bad.ang

@@ -0,0 +1,40 @@
+import "lib/math.ang"
+
+primes := [2]
+
+func is_prime(x: number) boolean {
+    i := 0
+    while i < primes.length() && primes.at(i)*primes.at(i) < x {
+        if mod(x, primes.at(i)) == 0 {
+            return false
+        }
+        i = i + 1
+    }
+
+    return true
+}
+
+n := 1
+max := 100000
+
+while n < max {
+    n = n + 2
+
+    if is_prime(n) {
+        primes.append(n)
+
+        # Update counter
+        print(char(0x0D))
+        print(str(n))
+        print("/")
+        print(str(max))
+        print(char(0x09))
+        print(str(roundd(n/max*100, 2)))
+        print("%")
+        print(char(0x09))
+        print(str(primes.length()))
+        print(" primes")
+    }
+}
+
+write(str(primes))

chars.ang

@@ -0,0 +1,15 @@
+
+MAX_WIDTH := 16
+
+print(" ")
+w := 1
+n := 0x21
+while n < 0xA0 {
+    print(char(n))
+    n = n + 1
+    w = w + 1
+    if w >= MAX_WIDTH {
+        write("")
+        w = 0
+    }
+}

cli/main.go

@@ -1,10 +1,13 @@
 package main
 
 import (
+	"bufio"
+	"errors"
 	"github.com/alecthomas/kong"
 	"log"
 	"neemek.com/anglais/core"
 	"os"
+	"path"
 	"path/filepath"
 )
 
@@ -13,6 +16,7 @@ type Context struct {
 }
 
 type RunCmd struct {
+	IgnoreWarnings bool   `name:"ignore-warnings" help:"Ignore warning messages"`
 	Bytecode       bool   `name:"bytecode" short:"c" help:"Run file as if it's bytecode"`
 	File           string `arg:"" name:"file" help:"File to read program from" type:"existingfile"`
 }
@@ -22,45 +26,34 @@ type WorkingDirectoryResolver struct {
 	workingDirectory string
 }
 
-func (r *WorkingDirectoryResolver) Resolve(path string) (core.Node, error) {
+func (r *WorkingDirectoryResolver) Resolve(path string) (string, error) {
 	pth := filepath.Join(r.workingDirectory, path)
 	f, err := os.ReadFile(pth)
 	if err != nil {
-		return nil, err
+		return "", err
 	}
 
-	str := string(f)
+	return string(f), nil
-
-	l := core.NewLexer(str)
-
-	tokens, err := l.Tokenize()
-	if err != nil {
-		return nil, err
-	}
-
-	p := core.NewParser(tokens)
-
-	tree, err := p.Parse()
-	if err != nil {
-		return nil, err
-	}
-
-	return tree, nil
 }
 
-func (cmd *RunCmd) Run(ctx *Context) error {
+func (r *WorkingDirectoryResolver) IsSame(a, b string) bool {
+	apath := filepath.Clean(filepath.Join(r.workingDirectory, a))
+	bpath := filepath.Clean(filepath.Join(r.workingDirectory, b))
+
+	return apath == bpath
+}
+
+func makeChunk(ctx *Context, fpath string, ignoreWarnings bool) (*core.Chunk, error) {
 	if ctx.Debug {
 		log.Println("Reading file")
 	}
 
-	f, err := os.ReadFile(cmd.File)
+	f, err := os.ReadFile(fpath)
 
 	if err != nil {
-		return err
+		return nil, err
 	}
 
-	var chunk *core.Chunk
-	if !cmd.Bytecode {
 	src := string(f)
 
 	if ctx.Debug {
@@ -74,41 +67,50 @@ func (cmd *RunCmd) Run(ctx *Context) error {
 	tokens, err := l.Tokenize()
 
 	if err != nil {
-			log.Fatal(err)
+		return nil, err
 	}
 
 	if len(tokens) <= 1 {
-			log.Fatal("Empty file")
+		return nil, errors.New("empty file")
 	}
 
 	if ctx.Debug {
 		log.Printf("Lexed %d tokens", len(tokens))
 
 	}
-		p := core.NewParser(tokens)
+	p := core.NewParser(src, tokens)
 
 	if ctx.Debug {
 		log.Println("Initialized parser")
 	}
 
-		tree, err := p.Parse()
+	pathat, err := filepath.Abs(fpath)
+	if err != nil {
+		return nil, err
+	}
+
+	tree, err := p.Parse(pathat)
+
+	if ctx.Debug {
+		log.Printf("Parsed tree, meaning:\n%s", tree)
+	}
 
 	// if there were parsing errors, print them out
 	if err != nil {
-			print(err.(*core.ParsingError).Format([]rune(src)))
+		print(err.(core.ParsingError).Format())
 		log.Fatal("Parsing had errors")
 	}
 
 	if ctx.Debug {
 		log.Println("Initialized compiler")
 	}
-		c := core.NewCompiler()
+	c := core.NewCompiler([]rune(src))
 
 	if ctx.Debug {
 		log.Println("Setting imports resolver")
 	}
 
-		dir, _ := filepath.Split(cmd.File)
+	dir, _ := path.Split(fpath)
 	c.SetImportsResolver(&WorkingDirectoryResolver{
 		dir,
 	})
@@ -117,12 +119,44 @@ func (cmd *RunCmd) Run(ctx *Context) error {
 		log.Println("Compiling parse tree")
 	}
 	err = c.Compile(tree)
+	if err != nil {
+		var e core.FormatedError
+		if errors.As(err, &e) {
+			log.Fatal(e.Format())
+		}
+		log.Fatal(err)
+	}
+
+	// if there were non-critical warnings, report them
+	if !ignoreWarnings && len(c.Warnings) != 0 {
+		for _, warning := range c.Warnings {
+			log.Println(warning.Format())
+		}
+		log.Fatal("compiler reported warning(s) (ignore warnings with the --ignore-warnings option)")
+	}
+
+	return c.Chunk, nil
+}
+
+func (cmd *RunCmd) Run(ctx *Context) error {
+	var chunk *core.Chunk
+	if !cmd.Bytecode {
+		c, err := makeChunk(ctx, cmd.File, cmd.IgnoreWarnings)
+		if err != nil {
+			return err
+		}
+		chunk = c
+	} else {
+		if ctx.Debug {
+			log.Println("Reading file")
+		}
+
+		f, err := os.ReadFile(cmd.File)
+
 		if err != nil {
 			return err
 		}
 
-		chunk = c.Chunk
-	} else {
 		if ctx.Debug {
 			log.Println("Registering GOB types")
 		}
@@ -159,70 +193,11 @@ func (cmd *RunCmd) Run(ctx *Context) error {
 type CompileCmd struct {
 	File           string `arg:"" name:"file" help:"File to compile program from" type:"existingfile"`
 	Output         string `arg:"" name:"output" help:"File path to output bytecode to" type:"path"`
+	IgnoreWarnings bool   `name:"ignore-warnings" help:"Ignore warning messages"`
 }
 
 func (cmd *CompileCmd) Run(ctx *Context) error {
-	if ctx.Debug {
+	c, err := makeChunk(ctx, cmd.File, cmd.IgnoreWarnings)
-		log.Println("Reading file")
-	}
-
-	f, err := os.ReadFile(cmd.File)
-
-	if err != nil {
-		return err
-	}
-
-	src := string(f)
-
-	if ctx.Debug {
-		log.Println("Initializing lexer")
-	}
-	l := core.NewLexer(src)
-
-	if ctx.Debug {
-		log.Println("Lexing all tokens")
-	}
-	tokens, err := l.Tokenize()
-
-	if err != nil {
-		log.Fatal(err)
-	}
-
-	if ctx.Debug {
-		log.Println("Initializing parser")
-	}
-	p := core.NewParser(tokens)
-
-	if ctx.Debug {
-		log.Println("Parsing tree")
-	}
-
-	tree, err := p.Parse()
-
-	if err != nil {
-		print(err.(*core.ParsingError).Format([]rune(src)))
-	}
-
-	if ctx.Debug {
-		log.Println("Initialized compiler")
-	}
-
-	c := core.NewCompiler()
-
-	if ctx.Debug {
-		log.Println("Setting import resolver")
-	}
-
-	dir, _ := filepath.Split(cmd.File)
-	c.SetImportsResolver(&WorkingDirectoryResolver{
-		dir,
-	})
-
-	if ctx.Debug {
-		log.Println("Compiling parse tree")
-	}
-
-	err = c.Compile(tree)
 	if err != nil {
 		return err
 	}
@@ -237,7 +212,7 @@ func (cmd *CompileCmd) Run(ctx *Context) error {
 		log.Println("Serializing chunk")
 	}
 
-	serialized := c.Chunk.Serialize()
+	serialized := c.Serialize()
 
 	if ctx.Debug {
 		log.Println("Writing file")
@@ -252,11 +227,59 @@ func (cmd *CompileCmd) Run(ctx *Context) error {
 	return nil
 }
 
+type ReplCmd struct {
+}
+
+func (cmd *ReplCmd) Run(ctx *Context) error {
+	c := core.NewCompiler([]rune(""))
+	vm := core.NewVM(core.NewChunk([]core.Bytecode{}, []core.Value{}), 256, 256)
+
+	reader := bufio.NewReader(os.Stdin)
+	for {
+		print("> ")
+		src, err := reader.ReadString('\n')
+		if err != nil {
+			return err
+		}
+
+		l := core.NewLexer(src)
+		tokens, err := l.Tokenize()
+		if err != nil {
+			log.Println(err)
+			continue
+		}
+
+		p := core.NewParser(src, tokens)
+		prog, err := p.Parse("REPL")
+		if err != nil {
+			var e core.FormatedError
+			if errors.As(err, &e) {
+				log.Print(e.Format())
+			}
+			continue
+		}
+
+		c.SetSource(src)
+		if err = c.Compile(prog); err != nil {
+			var e core.FormatedError
+			if errors.As(err, &e) {
+				log.Print(e.Format())
+			}
+			continue
+		}
+
+		vm.SetChunk(c.Chunk)
+		for vm.Next() {
+		}
+	}
+}
+
 var cli struct {
 	Debug bool `short:"D" name:"debug" help:"Enable debug mode."`
 
 	Run     RunCmd     `cmd:"" name:"run" help:"Run program."`
-	CompileCmd CompileCmd `cmd:"" name:"compile" help:"Compile program to bytecode."`
+	Compile CompileCmd `cmd:"" name:"compile" help:"Compile program to bytecode."`
+	Repl    ReplCmd    `cmd:"" name:"repl" help:"Start a REPL loop."`
 }
 
 func main() {

codegen.ang

@@ -0,0 +1,24 @@
+
+passphrase := "Hello world!".split("")
+start := [0, 0, 0]
+modulus := 10
+base := byte("!")
+
+i := 0
+n := 0
+while n < passphrase.length() {
+    b := byte(passphrase.at(n))
+
+    v = start.at(i) + b - base
+    while v >= modulus {
+        v = v - modulus
+    }
+
+    start.put(i, v)
+
+    if i >= 3 {
+        i = 0
+    }
+    n = n + 1
+}
+

core/all_test.go

@@ -22,13 +22,22 @@ func GetAllTestCases() map[string]AllTestCase {
 			},
 		},
 		"func": {
-			"func sum(a, b) {\n\treturn a + b\n}\nsum(1, 2)",
+			"func sum(a: number, b: number) number {\n\treturn a + b\n}\n_ = sum(1, 2)",
 			[]Value{
 				&VariableValue{
 					"sum",
 					&FunctionValue{
 						Name: "sum",
-						Params: []string{"a", "b"},
+						Params: []FunctionParameter{
+							{
+								"a",
+								&NumberSignature{},
+							},
+							{
+								"b",
+								&NumberSignature{},
+							},
+						},
 						Chunk: &Chunk{
 							Bytecode: []Bytecode{
 								InstructionDescend,
@@ -45,6 +54,63 @@ func GetAllTestCases() map[string]AllTestCase {
 				},
 			},
 		},
+		"list": {
+			"a := [1, 2]",
+			[]Value{
+				&VariableValue{
+					"a",
+					&ListValue{
+						[]Value{
+							&NumberValue{1},
+							&NumberValue{2},
+						},
+					},
+					0,
+				},
+			},
+		},
+		"constant_list_concat": {
+			"a := [1, 2] + [3]",
+			[]Value{
+				&VariableValue{
+					"a",
+					&ListValue{
+						[]Value{
+							&NumberValue{1},
+							&NumberValue{2},
+							&NumberValue{3},
+						},
+					},
+					0,
+				},
+			},
+		},
+		"list_concat": {
+			"a := [1, 2]\nb := a + [3]",
+			[]Value{
+				&VariableValue{
+					"a",
+					&ListValue{
+						[]Value{
+							&NumberValue{1},
+							&NumberValue{2},
+						},
+					},
+					0,
+				},
+				&VariableValue{
+					"b",
+					&ListValue{
+						[]Value{
+							&NumberValue{1},
+							&NumberValue{2},
+							&NumberValue{3},
+						},
+					},
+					0,
+				},
+			},
+		},
 	}
 }
 
@@ -64,18 +130,18 @@ func TestAll(t *testing.T) {
 			}
 
 			t.Log("Initializing parser")
-			p := NewParser(tokens)
+			p := NewParser(tc.src, tokens)
 
 			t.Log("Parsing tokens")
-			tree, err := p.Parse()
+			tree, err := p.Parse(tc.src)
 
 			if err != nil {
-				print(err.(*ParsingError).Format([]rune(tc.src)))
+				print(err.(ParsingError).Format())
 				t.Fatalf("parser had an error")
 			}
 
 			t.Log("Initializing compiler")
-			c := NewCompiler()
+			c := NewCompiler([]rune(tc.src))
 
 			t.Log("Compiling parse tree")
 			err = c.Compile(tree)
@@ -107,10 +173,10 @@ func BenchmarkAll(b *testing.B) {
 				l := NewLexer(tc.src)
 				tokens, _ := l.Tokenize()
 
-				p := NewParser(tokens)
+				p := NewParser(tc.src, tokens)
-				tree, _ := p.Parse()
+				tree, _ := p.Parse(tc.src)
 
-				c := NewCompiler()
+				c := NewCompiler([]rune(tc.src))
 				_ = c.Compile(tree)
 
 				vm := NewVM(c.Chunk, 256, 256)

core/compiler_test.go

@@ -6,7 +6,7 @@ import (
 )
 
 func TestNewCompiler(t *testing.T) {
-	c := NewCompiler()
+	c := NewCompiler([]rune{})
 
 	if c == nil {
 		t.Fatal("NewCompiler returned nil")
@@ -23,39 +23,63 @@ func TestNewCompiler(t *testing.T) {
 
 func BenchmarkNewCompiler(b *testing.B) {
 	for i := 0; i < b.N; i++ {
-		_ = NewCompiler()
+		_ = NewCompiler([]rune{})
 	}
 }
 
 type CompileTestData struct {
-	tree          Node
+	program       *Program
 	expectedStack []Value
 }
 
 func GetCompileTestData() map[string]CompileTestData {
 	return map[string]CompileTestData{
 		"constant_string": {
+			&Program{
+				[]string{},
+				&BlockNode{
+					[]Node{
+						&AssignNode{
+							"a",
 							&StringNode{
 								"Hello world!",
 								"\"Hello world!\"",
+								0, 0,
+							},
+							true,
+							0, 0,
+						},
+					},
+					0, 0,
+				},
+				"",
 			},
 			[]Value{
+				&VariableValue{
+					"a",
 					&StringValue{"Hello world!"},
+					0,
+				},
 			},
 		},
 		"conditional_false": {
+			&Program{
+				[]string{},
 				&BlockNode{
 					[]Node{
 						&AssignNode{
 							"a",
 							&NumberNode{
 								0,
+								0, 0,
 							},
 							true,
+							0, 0,
 						},
 						&ConditionalNode{
 							&BooleanNode{
 								false,
+								0, 0,
 							},
 							&BlockNode{
 								[]Node{
@@ -63,14 +87,21 @@ func GetCompileTestData() map[string]CompileTestData {
 										"a",
 										&NumberNode{
 											1,
+											0, 0,
 										},
 										false,
+										0, 0,
 									},
 								},
+								0, 0,
 							},
 							nil,
+							0, 0,
 						},
 					},
+					0, 0,
+				},
+				"",
 			},
 			[]Value{
 				&VariableValue{
@@ -81,18 +112,23 @@ func GetCompileTestData() map[string]CompileTestData {
 			},
 		},
 		"conditional_true": {
+			&Program{
+				[]string{},
 				&BlockNode{
 					[]Node{
 						&AssignNode{
 							"a",
 							&NumberNode{
 								0,
+								0, 0,
 							},
 							true,
+							0, 0,
 						},
 						&ConditionalNode{
 							&BooleanNode{
 								true,
+								0, 0,
 							},
 							&BlockNode{
 								[]Node{
@@ -100,14 +136,21 @@ func GetCompileTestData() map[string]CompileTestData {
 										"a",
 										&NumberNode{
 											1,
+											0, 0,
 										},
 										false,
+										0, 0,
 									},
 								},
+								0, 0,
 							},
 							nil,
+							0, 0,
 						},
 					},
+					0, 0,
+				},
+				"",
 			},
 			[]Value{
 				&VariableValue{
@@ -118,18 +161,23 @@ func GetCompileTestData() map[string]CompileTestData {
 			},
 		},
 		"conditional_else_false": {
+			&Program{
+				[]string{},
 				&BlockNode{
 					[]Node{
 						&AssignNode{
 							"a",
 							&NumberNode{
 								0,
+								0, 0,
 							},
 							true,
+							0, 0,
 						},
 						&ConditionalNode{
 							&BooleanNode{
 								false,
+								0, 0,
 							},
 							&BlockNode{
 								[]Node{
@@ -137,10 +185,13 @@ func GetCompileTestData() map[string]CompileTestData {
 										"a",
 										&NumberNode{
 											1,
+											0, 0,
 										},
 										false,
+										0, 0,
 									},
 								},
+								0, 0,
 							},
 							&BlockNode{
 								[]Node{
@@ -148,13 +199,20 @@ func GetCompileTestData() map[string]CompileTestData {
 										"a",
 										&NumberNode{
 											2,
+											0, 0,
 										},
 										false,
+										0, 0,
 									},
 								},
+								0, 0,
+							},
+							0, 0,
 						},
 					},
+					0, 0,
 				},
+				"",
 			},
 			[]Value{
 				&VariableValue{
@@ -165,18 +223,23 @@ func GetCompileTestData() map[string]CompileTestData {
 			},
 		},
 		"conditional_else_true": {
+			&Program{
+				[]string{},
 				&BlockNode{
 					[]Node{
 						&AssignNode{
 							"a",
 							&NumberNode{
 								0,
+								0, 0,
 							},
 							true,
+							0, 0,
 						},
 						&ConditionalNode{
 							&BooleanNode{
 								true,
+								0, 0,
 							},
 							&BlockNode{
 								[]Node{
@@ -184,10 +247,13 @@ func GetCompileTestData() map[string]CompileTestData {
 										"a",
 										&NumberNode{
 											1,
+											0, 0,
 										},
 										false,
+										0, 0,
 									},
 								},
+								0, 0,
 							},
 							&BlockNode{
 								[]Node{
@@ -195,13 +261,20 @@ func GetCompileTestData() map[string]CompileTestData {
 										"a",
 										&NumberNode{
 											2,
+											0, 0,
 										},
 										false,
+										0, 0,
 									},
 								},
+								0, 0,
+							},
+							0, 0,
 						},
 					},
+					0, 0,
 				},
+				"",
 			},
 			[]Value{
 				&VariableValue{
@@ -212,41 +285,89 @@ func GetCompileTestData() map[string]CompileTestData {
 			},
 		},
 		"addition": {
+			&Program{
+				[]string{},
+				&BlockNode{
+					[]Node{
+						&AssignNode{
+							"a",
 							&BinaryNode{
 								BinaryAddition,
 								&NumberNode{
 									1,
+									0, 0,
 								},
 								&NumberNode{
 									2,
+									0, 0,
 								},
+								0, 0,
+							},
+							true,
+							0, 0,
+						},
+					},
+					0, 0,
+				},
+				"",
 			},
 			[]Value{
+				&VariableValue{
+					"a",
 					&NumberValue{3},
+					0,
 				},
 			},
-		"sum_function": {&BlockNode{
+		},
+		"sum_function": {
+			&Program{
+				[]string{},
+				&BlockNode{
 					[]Node{
 						&AssignNode{
 							"sum",
 							&FunctionNode{
 								"sum",
-						[]string{"a", "b"},
+								[]FunctionParameter{
+									{
+										"a",
+										&NumberSignature{},
+									},
+									{
+										"b",
+										&NumberSignature{},
+									},
+								},
+								&NumberSignature{},
 								&BlockNode{
 									[]Node{
 										&ReturnNode{
 											&BinaryNode{
 												BinaryAddition,
-										&ReferenceNode{"a"},
+												&ReferenceNode{
-										&ReferenceNode{"b"},
+													"a",
-									},
+													0, 0,
+												},
+												&ReferenceNode{
+													"b",
+													0, 0,
+												},
+												0, 0,
+											},
+											0, 0,
 										},
 									},
+									0, 0,
 								},
+								0, 0,
 							},
 							true,
+							0, 0,
 						},
 					},
+					0, 0,
+				},
+				"",
 			},
 			[]Value{
 				&VariableValue{
@@ -254,7 +375,17 @@ func GetCompileTestData() map[string]CompileTestData {
 
 					&FunctionValue{
 						"sum",
-						[]string{"a", "b"},
+						[]FunctionParameter{
+							{
+								"a",
+								&NumberSignature{},
+							},
+							{
+								"b",
+								&NumberSignature{},
+							},
+						},
+						&NumberSignature{},
 						NewChunk(
 							[]Bytecode{
 								InstructionDescend,
@@ -275,43 +406,63 @@ func GetCompileTestData() map[string]CompileTestData {
 			},
 		},
 		"remove_func_vars": {
+			&Program{
+				[]string{},
 				&BlockNode{
 					[]Node{
 						&AssignNode{
 							"a",
 							&FunctionNode{
 								"a",
-							[]string{},
+								[]FunctionParameter{},
+								&NumberSignature{},
 								&BlockNode{
 									[]Node{
 										&AssignNode{
 											"b",
-										&NumberNode{1},
+											&NumberNode{
+												1,
+												0, 0,
+											},
 											true,
+											0, 0,
 										},
 										&ReturnNode{
-										&ReferenceNode{"b"},
+											&ReferenceNode{
+												"b",
+												0, 0,
+											},
+											0, 0,
 										},
 									},
+									0, 0,
 								},
+								0, 0,
 							},
 							true,
+							0, 0,
 						},
 						&CallNode{
 							&ReferenceNode{
 								"a",
+								0, 0,
 							},
 							[]Node{},
 							false,
+							0, 0,
 						},
 					},
+					0, 0,
+				},
+				"",
 			},
 			[]Value{
 				&VariableValue{
 					"a",
 					&FunctionValue{
 						"a",
-						[]string{},
+						[]FunctionParameter{},
+						&NumberSignature{},
 						NewChunk(
 							[]Bytecode{
 								InstructionDescend,
@@ -331,6 +482,58 @@ func GetCompileTestData() map[string]CompileTestData {
 				},
 			},
 		},
+		"two_lists": {
+			program: &Program{
+				[]string{},
+				&BlockNode{
+					statements: []Node{
+						&AssignNode{
+							name: "a",
+							value: &ListNode{
+								items: []Node{
+									&NumberNode{value: 1},
+									&NumberNode{value: 2},
+								},
+							},
+							declare: true,
+						},
+						&AssignNode{
+							name: "b",
+							value: &ListNode{
+								items: []Node{
+									&StringNode{value: "Hello"},
+									&StringNode{value: "world"},
+								},
+							},
+							declare: true,
+						},
+					},
+				},
+				"",
+			},
+			expectedStack: []Value{
+				&VariableValue{
+					name: "a",
+					value: &ListValue{
+						Items: []Value{
+							&NumberValue{1},
+							&NumberValue{2},
+						},
+					},
+					scope: 0,
+				},
+				&VariableValue{
+					name: "b",
+					value: &ListValue{
+						Items: []Value{
+							&StringValue{"Hello"},
+							&StringValue{"world"},
+						},
+					},
+					scope: 0,
+				},
+			},
+		},
 	}
 }
 
@@ -343,7 +546,7 @@ func printChunk(t *testing.T, name string, chunk *Chunk) {
 	t.Logf("=-= constants =-=")
 
 	for i, ct := range chunk.Constants {
-		t.Logf("c=%d \t%s", i, ct)
+		t.Logf("c=%d \t%s", i, ct.DebugString())
 
 		f, ok := ct.(*FunctionValue)
 		if ok {
@@ -360,10 +563,10 @@ func TestCompile(t *testing.T) {
 	for name, testCase := range data {
 		t.Run(name, func(t *testing.T) {
 			t.Log("Initializing compiler")
-			c := NewCompiler()
+			c := NewCompiler([]rune(testCase.program.String()))
 
 			t.Log("Compiling node tree")
-			err := c.Compile(testCase.tree)
+			err := c.Compile(testCase.program)
 			if err != nil {
 				t.Fatalf("Compiling failed: %v", err)
 			}
@@ -389,8 +592,8 @@ func BenchmarkCompile(b *testing.B) {
 	for name, testCase := range data {
 		b.Run(name, func(b *testing.B) {
 			for i := 0; i < b.N; i++ {
-				c := NewCompiler()
+				c := NewCompiler([]rune{})
-				_ = c.Compile(testCase.tree)
+				_ = c.Compile(testCase.program)
 			}
 		})
 	}
@@ -399,7 +602,7 @@ func BenchmarkCompile(b *testing.B) {
 func TestCompiler_AddU16(t *testing.T) {
 	for i := 0; i <= 0xffff; i++ {
 		t.Run(fmt.Sprint(i), func(t *testing.T) {
-			c := NewCompiler()
+			c := NewCompiler([]rune{})
 			c.addU16(uint16(i))
 
 			if c.Chunk.Bytecode[0] != Bytecode(i>>8) {
@@ -417,24 +620,9 @@ func TestCompiler_CleanStack(t *testing.T) {
 	cases := GetCompileTestData()
 
 	for name, tc := range cases {
-		switch tc.tree.Type() {
-		// skip all expected unclean nodes
-		case StringNodeType, NumberNodeType, ReferenceNodeType, BooleanNodeType, NilNodeType, BinaryNodeType, ReturnNodeType:
-			continue
-
-		case CallNodeType:
-			if tc.tree.(*CallNode).keep {
-				// if we know it should be unclean, skip it
-				continue
-			}
-
-		// clean statements
-		default:
-		}
-
 		t.Run(name, func(t *testing.T) {
-			c := NewCompiler()
+			c := NewCompiler([]rune(tc.program.String()))
-			err := c.Compile(tc.tree)
+			err := c.Compile(tc.program)
 			if err != nil {
 				t.Fatalf("Compiling failed: %v", err)
 			}

core/lexer.go

@@ -29,6 +29,7 @@ const (
 	TokenSemicolon
 
 	TokenNumber
+	TokenHexadecimal
 	TokenString
 	TokenName
 
@@ -53,6 +54,7 @@ const (
 
 	TokenComma
 	TokenDot
+	TokenColon
 
 	TokenAssign
 	TokenDeclare
@@ -64,6 +66,7 @@ const (
 	TokenLessThanOrEqual
 
 	TokenDoubleAmpersand
+	TokenPipe
 	TokenDoublePipe
 
 	TokenBreakpoint
@@ -153,6 +156,12 @@ func (t TokenType) String() string {
 		return "close bracket"
 	case TokenImport:
 		return "import"
+	case TokenColon:
+		return "colon"
+	case TokenPipe:
+		return "pipe"
+	case TokenHexadecimal:
+		return "hexadecimal"
 	}
 
 	return "UNDEFINED TOKENTYPE STRING CONVERSION"
@@ -234,11 +243,11 @@ func (l *Lexer) NextToken() (Token, error) {
 	case '.':
 		return l.makeToken(TokenDot), nil
 	case ':':
-		if !l.accept('=') {
+		if l.accept('=') {
-			return l.makeToken(TokenError), errors.New("malformed token (got ':', expected '=' to follow)")
+			return l.makeToken(TokenDeclare), nil
 		}
 
-		return l.makeToken(TokenDeclare), nil
+		return l.makeToken(TokenColon), nil
 	case '!':
 		if l.accept('=') {
 			return l.makeToken(TokenBangEquals), nil
@@ -276,7 +285,7 @@ func (l *Lexer) NextToken() (Token, error) {
 			return l.makeToken(TokenDoublePipe), nil
 		}
 
-		return l.makeToken(TokenError), errors.New("malformed token (got '|', expected '|' to follow)")
+		return l.makeToken(TokenPipe), nil
 
 	case '"':
 		// include ending quote
@@ -327,6 +336,19 @@ func (l *Lexer) NextToken() (Token, error) {
 			default:
 				return l.makeToken(TokenName), nil
 			}
+		} else if c == '0' && l.peek() != '.' {
+			if l.peek() == 'x' {
+				l.advance()
+
+				// hex
+				for unicode.In(l.peek(), unicode.Hex_Digit) {
+					l.advance()
+				}
+
+				return l.makeToken(TokenHexadecimal), nil
+			}
+
+			return l.makeToken(TokenNumber), nil
 		} else if unicode.IsDigit(c) {
 			for unicode.IsDigit(l.peek()) {
 				l.advance()

core/nodes.go

@@ -11,6 +11,8 @@ type NodeType int
 type Node interface {
 	Type() NodeType
 	String() string
+
+	Bounds() (Pos, Pos)
 }
 
 const (
@@ -21,6 +23,7 @@ const (
 	NilNodeType
 	ListNodeType
 	BinaryNodeType
+	UnaryNodeType
 	BlockNodeType
 	ConditionalNodeType
 	LoopNodeType
@@ -29,7 +32,6 @@ const (
 	FunctionNodeType
 	ReturnNodeType
 	AccessNodeType
-	ImportNodeType
 	BreakpointNodeType
 )
 
@@ -67,8 +69,8 @@ func (n NodeType) String() string {
 		return "Access"
 	case BreakpointNodeType:
 		return "Breakpoint"
-	case ImportNodeType:
+	case UnaryNodeType:
-		return "Import"
+		return "Unary"
 	}
 	return "Invalid Node Type"
 }
@@ -76,6 +78,9 @@ func (n NodeType) String() string {
 // ReferenceNode a reference to a variable on the stack
 type ReferenceNode struct {
 	name string
+
+	start Pos
+	end   Pos
 }
 
 func (n ReferenceNode) Type() NodeType {
@@ -86,10 +91,17 @@ func (n ReferenceNode) String() string {
 	return n.name
 }
 
+func (n ReferenceNode) Bounds() (Pos, Pos) {
+	return n.start, n.end
+}
+
 // StringNode string/text values
 type StringNode struct {
 	value  string
 	quoted string
+
+	start Pos
+	end   Pos
 }
 
 func (n StringNode) Type() NodeType {
@@ -100,8 +112,15 @@ func (n StringNode) String() string {
 	return n.quoted
 }
 
+func (n StringNode) Bounds() (Pos, Pos) {
+	return n.start, n.end
+}
+
 type NumberNode struct {
 	value float64
+
+	start Pos
+	end   Pos
 }
 
 func (n NumberNode) Type() NodeType {
@@ -112,9 +131,17 @@ func (n NumberNode) String() string {
 	return strconv.FormatFloat(n.value, 'g', -1, NumberSize)
 }
 
+func (n NumberNode) Bounds() (Pos, Pos) {
+	return n.start, n.end
+}
+
 // ListNode a list or sequence of values (items)
 type ListNode struct {
 	items   []Node
+	content TypeSignature
+
+	start Pos
+	end   Pos
 }
 
 func (n ListNode) Type() NodeType {
@@ -125,18 +152,25 @@ func (n ListNode) String() string {
 	sb := strings.Builder{}
 	sb.WriteString("[")
 	for i, item := range n.items {
-		sb.WriteString(item.String())
 		if i > 0 {
 			sb.WriteString(", ")
 		}
+		sb.WriteString(item.String())
 	}
 	sb.WriteString("]")
 	return sb.String()
 }
 
+func (n ListNode) Bounds() (Pos, Pos) {
+	return n.start, n.end
+}
+
 type AccessNode struct {
 	source   Node
 	property string
+
+	start Pos
+	end   Pos
 }
 
 func (n AccessNode) Type() NodeType {
@@ -147,6 +181,10 @@ func (n AccessNode) String() string {
 	return fmt.Sprintf("(%s from %s)", n.property, n.source)
 }
 
+func (n AccessNode) Bounds() (Pos, Pos) {
+	return n.start, n.end
+}
+
 type BinaryOperation uint
 
 func (n BinaryOperation) String() string {
@@ -198,11 +236,45 @@ const (
 	BinaryGreaterEqual
 )
 
+func (n BinaryOperation) Symbol() string {
+	switch n {
+	case BinaryAddition:
+		return "+"
+	case BinarySubtraction:
+		return "-"
+	case BinaryMultiplication:
+		return "*"
+	case BinaryDivision:
+		return "/"
+	case BinaryEquality:
+		return "=="
+	case BinaryInequality:
+		return "!="
+	case BinaryLess:
+		return "<"
+	case BinaryGreater:
+		return ">"
+	case BinaryAnd:
+		return "&&"
+	case BinaryOr:
+		return "||"
+	case BinaryLessEqual:
+		return "<="
+	case BinaryGreaterEqual:
+		return ">="
+	}
+
+	panic("unsupported binary operation to symbol conversion for " + n.String())
+}
+
 // BinaryNode All operations which take 2 variables
 type BinaryNode struct {
 	BinaryOperation
 	Left  Node
 	Right Node
+
+	start Pos
+	end   Pos
 }
 
 func (n BinaryNode) Type() NodeType {
@@ -213,9 +285,65 @@ func (n BinaryNode) String() string {
 	return fmt.Sprintf("%s %s %s", n.Left.String(), n.BinaryOperation.String(), n.Right.String())
 }
 
+func (n BinaryNode) Bounds() (Pos, Pos) {
+	return n.start, n.end
+}
+
+type UnaryOperation int
+
+const (
+	UnaryNegate UnaryOperation = iota
+	UnaryNot
+)
+
+func (op UnaryOperation) String() string {
+	switch op {
+	case UnaryNegate:
+		return "negate"
+	case UnaryNot:
+		return "not"
+	}
+
+	panic("unimplemented unary operation to string conversion")
+}
+
+func (op UnaryOperation) Symbol() string {
+	switch op {
+	case UnaryNegate:
+		return "-"
+	case UnaryNot:
+		return "!"
+	}
+
+	panic("unimplemented unary operation to symbol conversion")
+}
+
+type UnaryNode struct {
+	UnaryOperation
+	value Node
+
+	start Pos
+	end   Pos
+}
+
+func (n UnaryNode) Type() NodeType {
+	return UnaryNodeType
+}
+
+func (n UnaryNode) String() string {
+	return fmt.Sprintf("%s %s", n.UnaryOperation.String(), n.value.String())
+}
+
+func (n UnaryNode) Bounds() (Pos, Pos) {
+	return n.start, n.end
+}
+
 // BooleanNode boolean value
 type BooleanNode struct {
 	value bool
+
+	start Pos
+	end   Pos
 }
 
 func (n BooleanNode) Type() NodeType {
@@ -226,8 +354,15 @@ func (n BooleanNode) String() string {
 	return strconv.FormatBool(n.value)
 }
 
+func (n BooleanNode) Bounds() (Pos, Pos) {
+	return n.start, n.end
+}
+
 // NilNode nil value
-type NilNode struct{}
+type NilNode struct {
+	start Pos
+	end   Pos
+}
 
 func (n NilNode) Type() NodeType {
 	return NilNodeType
@@ -237,9 +372,16 @@ func (n NilNode) String() string {
 	return "nil"
 }
 
+func (n NilNode) Bounds() (Pos, Pos) {
+	return n.start, n.end
+}
+
 // BlockNode block node with statements
 type BlockNode struct {
 	statements []Node
+
+	start Pos
+	end   Pos
 }
 
 func (n BlockNode) Type() NodeType {
@@ -257,16 +399,8 @@ func (n BlockNode) String() string {
 	return builder.String()
 }
 
-type ImportNode struct {
+func (n BlockNode) Bounds() (Pos, Pos) {
-	path string
+	return n.start, n.end
-}
-
-func (n ImportNode) Type() NodeType {
-	return ImportNodeType
-}
-
-func (n ImportNode) String() string {
-	return fmt.Sprintf("import %s", n.path)
 }
 
 // ConditionalNode conditionals (if statements)
@@ -274,6 +408,9 @@ type ConditionalNode struct {
 	condition Node
 	do        Node
 	otherwise Node
+
+	start Pos
+	end   Pos
 }
 
 func (n ConditionalNode) Type() NodeType {
@@ -281,13 +418,24 @@ func (n ConditionalNode) Type() NodeType {
 }
 
 func (n ConditionalNode) String() string {
+	if n.otherwise == nil {
+		return fmt.Sprintf("if %s then %s", n.condition.String(), n.do.String())
+	}
+
 	return fmt.Sprintf("if %s then %s otheriwise %s", n.condition.String(), n.do.String(), n.otherwise.String())
 }
 
+func (n ConditionalNode) Bounds() (Pos, Pos) {
+	return n.start, n.end
+}
+
 // LoopNode Loops (for/while)
 type LoopNode struct {
 	condition Node
 	do        Node
+
+	start Pos
+	end   Pos
 }
 
 func (n LoopNode) Type() NodeType {
@@ -298,11 +446,18 @@ func (n LoopNode) String() string {
 	return fmt.Sprintf("while %s loop %s", n.condition.String(), n.do.String())
 }
 
+func (n LoopNode) Bounds() (Pos, Pos) {
+	return n.start, n.end
+}
+
 // AssignNode assignment
 type AssignNode struct {
 	name    string
 	value   Node
 	declare bool
+
+	start Pos
+	end   Pos
 }
 
 func (n AssignNode) Type() NodeType {
@@ -313,11 +468,18 @@ func (n AssignNode) String() string {
 	return fmt.Sprintf("set %s to %s", n.name, n.value)
 }
 
+func (n AssignNode) Bounds() (Pos, Pos) {
+	return n.start, n.end
+}
+
 // CallNode function call
 type CallNode struct {
 	source Node
 	args   []Node
 	keep   bool
+
+	start Pos
+	end   Pos
 }
 
 func (n CallNode) Type() NodeType {
@@ -328,11 +490,24 @@ func (n CallNode) String() string {
 	return fmt.Sprintf("call %s with args (%s)", n.source.String(), n.args)
 }
 
+func (n CallNode) Bounds() (Pos, Pos) {
+	return n.start, n.end
+}
+
 // FunctionNode definition of function
 type FunctionNode struct {
 	name       string
-	params []string
+	parameters []FunctionParameter
+	yield      TypeSignature
 	logic      Node
+
+	start Pos
+	end   Pos
+}
+
+type FunctionParameter struct {
+	Name      string
+	Signature TypeSignature
 }
 
 func (n FunctionNode) Type() NodeType {
@@ -343,9 +518,16 @@ func (n FunctionNode) String() string {
 	return fmt.Sprintf("definition of %s, do %s", n.name, n.logic.String())
 }
 
+func (n FunctionNode) Bounds() (Pos, Pos) {
+	return n.start, n.end
+}
+
 // ReturnNode return a value out of this context
 type ReturnNode struct {
 	value Node
+
+	start Pos
+	end   Pos
 }
 
 func (n ReturnNode) Type() NodeType {
@@ -356,7 +538,14 @@ func (n ReturnNode) String() string {
 	return fmt.Sprintf("return %s", n.value)
 }
 
-type BreakpointNode struct{}
+func (n ReturnNode) Bounds() (Pos, Pos) {
+	return n.start, n.end
+}
+
+type BreakpointNode struct {
+	start Pos
+	end   Pos
+}
 
 func (n BreakpointNode) Type() NodeType {
 	return BreakpointNodeType
@@ -365,3 +554,7 @@ func (n BreakpointNode) Type() NodeType {
 func (n BreakpointNode) String() string {
 	return "breakpoint"
 }
+
+func (n BreakpointNode) Bounds() (Pos, Pos) {
+	return n.start, n.end
+}

core/parser.go

@@ -8,17 +8,24 @@ import (
 	"strings"
 )
 
+type FormatedError interface {
+	Error() string
+	Format() string
+}
+
 type ParsingError struct {
 	Description string
 	Causer      *Token
+	Source      string
 }
 
-func (p *ParsingError) Error() string {
+func (p ParsingError) Error() string {
 	return p.Description
 }
 
 // Format Print a rich and informative error
-func (p *ParsingError) Format(src []rune) string {
+func (p ParsingError) Format() string {
+	src := []rune(p.Source)
 	builder := strings.Builder{}
 
 	lineNumber := 1
@@ -38,13 +45,17 @@ func (p *ParsingError) Format(src []rune) string {
 		}
 	}
 
-	builder.WriteString(" \t v ")
+	descriptor := fmt.Sprintf("%d:%d", lineNumber, int(p.Causer.Start)-lineBeginning+1)
 	builder.WriteString(p.Description)
 	builder.WriteRune('\n')
 
-	builder.WriteString(fmt.Sprintf("  %d:%d\t | %s", lineNumber, int(p.Causer.Start)-lineBeginning+1, string(src[lineBeginning:lineEnd])))
+	builder.WriteString(descriptor)
+	builder.WriteString(" | ")
+	builder.WriteString(string(src[lineBeginning:lineEnd]))
 
-	builder.WriteString("\n\t ^")
+	builder.WriteString("\n")
+	builder.WriteString(strings.Repeat(" ", len(descriptor)))
+	builder.WriteString("  ")
 	for i := lineBeginning; i <= int(p.Causer.Start); i++ {
 		builder.WriteRune(' ')
 	}
@@ -58,20 +69,45 @@ func (p *ParsingError) Format(src []rune) string {
 }
 
 type Parser struct {
+	source string
 	tokens []Token
 	prev   *Token
 	curr   *Token
 	pos    Pos
 }
 
-func NewParser(tokens []Token) *Parser {
+func NewParser(source string, tokens []Token) *Parser {
 	return &Parser{
+		source: source,
 		tokens: tokens,
 		pos:    0,
 	}
 }
 
-func (p *Parser) Parse() (Node, error) {
+type Program struct {
+	Imports []string
+	Block   *BlockNode
+	Path    string
+}
+
+func (p *Program) String() string {
+	builder := strings.Builder{}
+
+	builder.WriteString("=== Imports ===\n")
+	for _, i := range p.Imports {
+		builder.WriteString(i)
+		builder.WriteString("\n")
+	}
+	builder.WriteString("===============\n")
+
+	builder.WriteString(p.Block.String())
+
+	return builder.String()
+}
+
+func (p *Parser) Parse(path string) (*Program, error) {
+	imports := make([]string, 0)
+
 	// top level statements
 	statements := make([]Node, 0)
 
@@ -79,17 +115,33 @@ func (p *Parser) Parse() (Node, error) {
 	p.advance()
 
 	for int(p.pos) < len(p.tokens) && p.curr.Type != TokenEOF {
+		if p.accept(TokenImport) {
+			if err := p.expect(TokenString, "import requires a path/name to import"); err != nil {
+				return nil, err
+			}
+
+			imports = append(imports, p.prev.Lexeme[1:len(p.prev.Lexeme)-1])
+		}
+
 		b, err := p.block(true)
 
 		if err != nil {
 			return nil, err
 		}
 
+		if b != nil {
 			statements = append(statements, b)
 		}
+	}
 
-	return &BlockNode{
+	return &Program{
-		statements: statements,
+		imports,
+		&BlockNode{
+			statements,
+			0,
+			p.curr.Start + p.curr.Length,
+		},
+		path,
 	}, nil
 }
 
@@ -107,9 +159,9 @@ func (p *Parser) accept(tokenType TokenType) bool {
 	return false
 }
 
-func (p *Parser) expect(tokenType TokenType) error {
+func (p *Parser) expect(tokenType TokenType, reason string) error {
 	if !p.accept(tokenType) {
-		return p.error("Expected token "+tokenType.String()+", got "+p.curr.Type.String(), p.curr)
+		return p.error(fmt.Sprintf("Expected token %s, got %s; %s", tokenType, p.curr.Type, reason), p.curr)
 	}
 	return nil
 }
@@ -134,9 +186,10 @@ func (p *Parser) advance() {
 }
 
 func (p *Parser) error(error string, causer *Token) error {
-	return &ParsingError{
+	return ParsingError{
 		Description: error,
 		Causer:      causer,
+		Source:      p.source,
 	}
 }
 
@@ -147,6 +200,8 @@ func (p *Parser) factor() (Node, error) {
 		return &StringNode{
 			(*p.prev).Lexeme[1 : len((*p.prev).Lexeme)-1],
 			(*p.prev).Lexeme,
+			p.prev.Start,
+			p.prev.Start + p.prev.Length,
 		}, nil
 
 	case TokenNumber:
@@ -159,17 +214,37 @@ func (p *Parser) factor() (Node, error) {
 
 		return &NumberNode{
 			num,
+			p.prev.Start,
+			p.prev.Start + p.prev.Length,
+		}, nil
+
+	case TokenHexadecimal:
+		p.advance()
+		start := (*p.prev).Start
+		num, err := strconv.ParseUint((*p.prev).Lexeme[2:], 16, NumberSize)
+		if err != nil {
+			return nil, err
+		}
+
+		return &NumberNode{
+			float64(num),
+			start,
+			p.prev.Start + p.prev.Length,
 		}, nil
 
 	case TokenTrue:
 		p.advance()
 		return &BooleanNode{
 			true,
+			p.prev.Start,
+			p.prev.Start + p.prev.Length,
 		}, nil
 	case TokenFalse:
 		p.advance()
 		return &BooleanNode{
 			false,
+			p.prev.Start,
+			p.prev.Start + p.prev.Length,
 		}, nil
 
 	case TokenNil:
@@ -178,11 +253,25 @@ func (p *Parser) factor() (Node, error) {
 
 	case TokenOpenBracket:
 		p.advance()
+		start := p.prev.Start
+
+		if p.accept(TokenCloseBracket) {
+			s, err := p.parseSignature()
+			if err != nil {
+				return nil, err
+			}
+			return &ListNode{
+				[]Node{},
+				s,
+				start,
+				p.prev.Start + p.prev.Length,
+			}, nil
+		}
 
 		var values []Node
 		for !p.accept(TokenCloseBracket) {
 			if len(values) > 0 {
-				if err := p.expect(TokenComma); err != nil {
+				if err := p.expect(TokenComma, "list values must be separated by a comma"); err != nil {
 					return nil, err
 				}
 			}
@@ -198,24 +287,48 @@ func (p *Parser) factor() (Node, error) {
 
 		return &ListNode{
 			values,
+			nil,
+			start,
+			p.prev.Start + p.prev.Length,
 		}, nil
 
 	// unary minus
 	case TokenMinus:
 		p.advance()
+		first := p.prev
+
 		f, err := p.factor()
 		if err != nil {
 			return nil, err
 		}
-		return &BinaryNode{
+		return &UnaryNode{
-			BinarySubtraction,
+			UnaryNegate,
-			&NumberNode{0},
 			f,
+			first.Start,
+			p.prev.Start + p.prev.Length,
+		}, nil
+
+	case TokenBang:
+		p.advance()
+		start := p.prev.Start
+
+		v, err := p.factor()
+		if err != nil {
+			return nil, err
+		}
+
+		return &UnaryNode{
+			UnaryNot,
+			v,
+			start,
+			p.prev.Start + p.prev.Length,
 		}, nil
 
 	case TokenName:
 		p.advance()
 		name := (*p.prev).Lexeme
+		start := p.prev.Start
+		nameEnd := start + p.prev.Length
 
 		if p.curr.Type == TokenOpenParenthesis {
 			args, err := p.parseArgs()
@@ -226,23 +339,39 @@ func (p *Parser) factor() (Node, error) {
 			return &CallNode{
 				&ReferenceNode{
 					name,
+					start,
+					nameEnd,
 				},
 				args,
 				true,
+				start,
+				p.prev.Start + p.prev.Length,
 			}, nil
 		}
 
 		return &ReferenceNode{
 			name,
+			start,
+			nameEnd,
 		}, nil
 
 	case TokenFunc:
 		p.advance()
+		start := p.prev.Start
+
 		params, err := p.parseParams()
 		if err != nil {
 			return nil, err
 		}
 
+		var sig TypeSignature = &NilSignature{}
+		if p.curr.Type != TokenOpenBrace {
+			sig, err = p.parseSignature()
+			if err != nil {
+				return nil, err
+			}
+		}
+
 		b, err := p.block(false)
 		if err != nil {
 			return nil, err
@@ -251,7 +380,10 @@ func (p *Parser) factor() (Node, error) {
 		return &FunctionNode{
 			"*",
 			params,
+			sig,
 			b,
+			start,
+			p.prev.Start + p.prev.Length,
 		}, nil
 
 	case TokenOpenParenthesis:
@@ -260,20 +392,20 @@ func (p *Parser) factor() (Node, error) {
 		if err != nil {
 			return nil, err
 		}
-		if err := p.expect(TokenCloseParenthesis); err != nil {
+		if err := p.expect(TokenCloseParenthesis, "an opened parenthesis must be closed"); err != nil {
 			return nil, err
 		}
 
 		return v, nil
 
 	default:
-		err := p.error("invalid factor", p.curr)
+		return nil, p.error("invalid factor", p.curr)
-		p.advance()
-		return nil, err
 	}
 }
 
 func (p *Parser) prop() (Node, error) {
+	start := p.curr.Start
+
 	v, err := p.factor()
 	if err != nil {
 		return nil, err
@@ -281,7 +413,7 @@ func (p *Parser) prop() (Node, error) {
 
 	// parse chains of prop-getting ( "".split().join().length.round() )
 	for p.accept(TokenDot) {
-		if err := p.expect(TokenName); err != nil {
+		if err := p.expect(TokenName, "property must be a name"); err != nil {
 			return nil, err
 		}
 		property := (*p.prev).Lexeme
@@ -289,6 +421,8 @@ func (p *Parser) prop() (Node, error) {
 		v = &AccessNode{
 			v,
 			property,
+			start,
+			p.prev.Start + p.prev.Length,
 		}
 
 		// if called, also add
@@ -302,6 +436,8 @@ func (p *Parser) prop() (Node, error) {
 				v,
 				args,
 				true,
+				start,
+				p.prev.Start + p.prev.Length,
 			}
 		}
 	}
@@ -310,6 +446,7 @@ func (p *Parser) prop() (Node, error) {
 }
 
 func (p *Parser) product() (Node, error) {
+	start := p.curr.Start
 	left, err := p.prop()
 	if err != nil {
 		return nil, err
@@ -331,6 +468,8 @@ func (p *Parser) product() (Node, error) {
 			op,
 			left,
 			f,
+			start,
+			p.prev.Start + p.prev.Length,
 		}
 	}
 
@@ -338,6 +477,8 @@ func (p *Parser) product() (Node, error) {
 }
 
 func (p *Parser) term() (Node, error) {
+	start := p.curr.Start
+
 	left, err := p.product()
 	if err != nil {
 		return nil, err
@@ -359,6 +500,8 @@ func (p *Parser) term() (Node, error) {
 			op,
 			left,
 			pr,
+			start,
+			p.prev.Start + p.prev.Length,
 		}
 	}
 
@@ -366,6 +509,7 @@ func (p *Parser) term() (Node, error) {
 }
 
 func (p *Parser) comparison() (Node, error) {
+	start := p.curr.Start
 	left, err := p.term()
 
 	if err != nil {
@@ -403,10 +547,13 @@ func (p *Parser) comparison() (Node, error) {
 		op,
 		left,
 		t,
+		start,
+		p.prev.Start + p.prev.Length,
 	}, nil
 }
 
 func (p *Parser) condition() (Node, error) {
+	start := p.curr.Start
 	left, err := p.comparison()
 	if err != nil {
 		return nil, err
@@ -434,12 +581,15 @@ func (p *Parser) condition() (Node, error) {
 		op,
 		left,
 		c,
+		start,
+		p.prev.Start + p.prev.Length,
 	}, nil
 }
 
 func (p *Parser) statement() (Node, error) {
 	switch (*p.curr).Type {
 	case TokenIf:
+		start := p.curr.Start
 		p.advance()
 
 		condition, err := p.condition()
@@ -470,20 +620,25 @@ func (p *Parser) statement() (Node, error) {
 			condition,
 			then,
 			otherwise,
+			start,
+			p.prev.Start + p.prev.Length,
 		}, nil
 
 	case TokenName:
 		p.advance()
+		start := p.prev.Start
 		name := (*p.prev).Lexeme
 
 		if (*p.curr).Type == TokenDot {
 			var v Node = &ReferenceNode{
 				name,
+				start,
+				p.prev.Start + p.prev.Length,
 			}
 
 			// parse chains of prop-getting ( "".split().join().length.round() )
 			for p.accept(TokenDot) {
-				if err := p.expect(TokenName); err != nil {
+				if err := p.expect(TokenName, "property must be name"); err != nil {
 					return nil, err
 				}
 				property := (*p.prev).Lexeme
@@ -491,6 +646,8 @@ func (p *Parser) statement() (Node, error) {
 				v = &AccessNode{
 					v,
 					property,
+					start,
+					p.prev.Start + p.prev.Length,
 				}
 
 				// if called, also add
@@ -504,6 +661,8 @@ func (p *Parser) statement() (Node, error) {
 						v,
 						args,
 						(*p.curr).Type == TokenDot, // if the chain is continued, keep the value.
+						start,
+						p.prev.Start + p.prev.Length,
 					}
 				}
 			}
@@ -518,9 +677,13 @@ func (p *Parser) statement() (Node, error) {
 			return &CallNode{
 				&ReferenceNode{
 					name,
+					start,
+					start + Pos(len(name)),
 				},
 				args,
 				false,
+				start,
+				p.prev.Start + p.prev.Length,
 			}, nil
 		} else if p.accept(TokenAssign) || p.accept(TokenDeclare) {
 			isDeclaration := p.prev.Type == TokenDeclare
@@ -533,28 +696,19 @@ func (p *Parser) statement() (Node, error) {
 				name,
 				c,
 				isDeclaration,
+				start,
+				p.prev.Start + p.prev.Length,
 			}, nil
-		} else {
-			return p.condition()
 		}
 
-	case TokenImport:
+		return nil, p.error("invalid statement", p.curr)
-		p.advance()
-
-		if err := p.expect(TokenString); err != nil {
-			return nil, err
-		}
-
-		path := p.prev.Lexeme[1 : len(p.prev.Lexeme)-1]
-
-		return &ImportNode{
-			path,
-		}, nil
 
 	case TokenFunc:
 		p.advance()
 
-		if err := p.expect(TokenName); err != nil {
+		funcStart := p.prev.Start
+
+		if err := p.expect(TokenName, "function must have a name"); err != nil {
 			return nil, err
 		}
 		name := p.prev.Lexeme
@@ -564,6 +718,14 @@ func (p *Parser) statement() (Node, error) {
 			return nil, err
 		}
 
+		var yield TypeSignature = &NilSignature{}
+		if p.curr.Type != TokenOpenBrace {
+			yield, err = p.parseSignature()
+			if err != nil {
+				return nil, err
+			}
+		}
+
 		b, err := p.block(false)
 		if err != nil {
 			return nil, err
@@ -574,13 +736,19 @@ func (p *Parser) statement() (Node, error) {
 			&FunctionNode{
 				name,
 				params,
+				yield,
 				b,
+				funcStart,
+				p.prev.Start + p.prev.Length,
 			},
 			true,
+			funcStart,
+			p.prev.Start + p.prev.Length,
 		}, nil
 
 	case TokenWhile:
 		p.advance()
+		start := p.prev.Start
 
 		c, err := p.condition()
 		if err != nil {
@@ -595,10 +763,13 @@ func (p *Parser) statement() (Node, error) {
 		return &LoopNode{
 			c,
 			b,
+			start,
+			p.prev.Start + p.prev.Length,
 		}, nil
 
 	case TokenReturn:
 		p.advance()
+		start := p.prev.Start
 
 		c, err := p.condition()
 		if err != nil {
@@ -607,6 +778,8 @@ func (p *Parser) statement() (Node, error) {
 
 		return &ReturnNode{
 			c,
+			start,
+			p.prev.Start + p.prev.Length,
 		}, nil
 
 	case TokenBreakpoint:
@@ -614,24 +787,33 @@ func (p *Parser) statement() (Node, error) {
 
 		return &BreakpointNode{}, nil
 
+	case TokenImport:
+		defer p.advance()
+		return nil, p.error("import statements must be top-level", p.curr)
+
 	default:
-		err := p.error("invalid statement", p.curr)
+		defer p.advance()
-		p.advance()
+		return nil, p.error("invalid statement", p.curr)
-		return nil, err
 	}
 }
 
 func (p *Parser) block(canBeStatement bool) (Node, error) {
 	if canBeStatement {
 		if !p.accept(TokenOpenBrace) {
+			if p.curr.Type == TokenEOF {
+				return nil, nil
+			}
+
 			return p.statement()
 		}
 	} else {
-		if err := p.expect(TokenOpenBrace); err != nil {
+		if err := p.expect(TokenOpenBrace, "a block is required"); err != nil {
 			return nil, err
 		}
 	}
 
+	start := p.prev.Start
+
 	statements := make([]Node, 0)
 
 	for !p.accept(TokenCloseBrace) {
@@ -646,13 +828,15 @@ func (p *Parser) block(canBeStatement bool) (Node, error) {
 
 	return &BlockNode{
 		statements,
+		start,
+		p.prev.Start + p.prev.Length,
 	}, nil
 }
 
 func (p *Parser) parseArgs() ([]Node, error) {
 	args := make([]Node, 0)
 
-	if err := p.expect(TokenOpenParenthesis); err != nil {
+	if err := p.expect(TokenOpenParenthesis, "arguments must be contained in parenthesis"); err != nil {
 		return nil, err
 	}
 
@@ -663,7 +847,7 @@ func (p *Parser) parseArgs() ([]Node, error) {
 		}
 		args = append(args, c)
 		for !p.accept(TokenCloseParenthesis) {
-			if err := p.expect(TokenComma); err != nil {
+			if err := p.expect(TokenComma, "arguments must be separated by comma"); err != nil {
 				return nil, err
 			}
 			c, err = p.condition()
@@ -678,30 +862,142 @@ func (p *Parser) parseArgs() ([]Node, error) {
 }
 
 // parseParams parse parameters and parentheses
-func (p *Parser) parseParams() ([]string, error) {
+func (p *Parser) parseParams() ([]FunctionParameter, error) {
-	if err := p.expect(TokenOpenParenthesis); err != nil {
+	if err := p.expect(TokenOpenParenthesis, "parameters must be in parentheses"); err != nil {
 		return nil, err
 	}
-	params := make([]string, 0)
+	params := make([]FunctionParameter, 0)
 
 	if p.accept(TokenName) {
 		name := (*p.prev).Lexeme
-		params = append(params, name)
+		if err := p.expect(TokenColon, "parameters must have a type separated by a colon"); err != nil {
-		for !p.accept(TokenCloseParenthesis) {
-			if err := p.expect(TokenComma); err != nil {
 			return nil, err
 		}
-			if err := p.expect(TokenName); err != nil {
+
+		t, err := p.parseSignature()
+		if err != nil {
+			return nil, err
+		}
+
+		params = append(params, FunctionParameter{
+			name,
+			t,
+		})
+		for !p.accept(TokenCloseParenthesis) {
+			if err := p.expect(TokenComma, "parameters must be separated by comma"); err != nil {
+				return nil, err
+			}
+			if err := p.expect(TokenName, "parameters must have a name (cannot have trailing comma)"); err != nil {
 				return nil, err
 			}
 			name = (*p.prev).Lexeme
-			params = append(params, name)
+			if err := p.expect(TokenColon, "parameters must have a type separated by a colon"); err != nil {
+				return nil, err
+			}
+
+			t, err := p.parseSignature()
+			if err != nil {
+				return nil, err
+			}
+
+			params = append(params, FunctionParameter{
+				name,
+				t,
+			})
 		}
 	} else {
-		if err := p.expect(TokenCloseParenthesis); err != nil {
+		if err := p.expect(TokenCloseParenthesis, "must close parameter list"); err != nil {
 			return nil, err
 		}
 	}
 
 	return params, nil
 }
+
+func (p *Parser) parseSignature() (TypeSignature, error) {
+	var s TypeSignature
+
+	if p.accept(TokenFunc) {
+		if err := p.expect(TokenOpenParenthesis, "func signature must have parentheses for parameters"); err != nil {
+			return nil, err
+		}
+
+		var in []TypeSignature
+
+		for !p.accept(TokenCloseParenthesis) {
+			if len(in) > 0 {
+				if err := p.expect(TokenComma, "parameter types must be separated by a comma"); err != nil {
+					return nil, err
+				}
+			}
+
+			sig, err := p.parseSignature()
+
+			if err != nil {
+				return nil, err
+			}
+
+			in = append(in, sig)
+		}
+
+		out, err := p.parseSignature()
+		if err != nil {
+			return nil, err
+		}
+
+		s = &FunctionSignature{
+			in,
+			out,
+		}
+	} else {
+		if err := p.expect(TokenName, "type must be a name"); err != nil {
+			return nil, err
+		}
+		name := (*p.prev).Lexeme
+
+		switch name {
+		case "string":
+			s = &StringSignature{}
+		case "number":
+			s = &NumberSignature{}
+		case "boolean":
+			s = &BooleanSignature{}
+		case "list":
+			if err := p.expect(TokenOpenBracket, "list must have content typed"); err != nil {
+				return nil, err
+			}
+
+			contents, err := p.parseSignature()
+			if err != nil {
+				return nil, err
+			}
+
+			if err := p.expect(TokenCloseBracket, "list must close parameter list"); err != nil {
+				return nil, err
+			}
+
+			s = &ListSignature{
+				contents,
+			}
+
+		case "any":
+			s = &AnySignature{}
+
+		default:
+			return nil, p.error("unsupported type: "+name, p.prev)
+		}
+	}
+
+	if p.accept(TokenPipe) {
+		other, err := p.parseSignature()
+		if err != nil {
+			return nil, err
+		}
+		return &CompositeSignature{
+			s,
+			other,
+		}, nil
+	}
+
+	return s, nil
+}

core/parser_test.go

@@ -1,14 +1,16 @@
 package core
 
 import (
+	"fmt"
 	"strconv"
+	"strings"
 	"testing"
 )
 
 func TestNewParser(t *testing.T) {
 	tokens := make([]Token, 0)
 
-	p := NewParser(tokens)
+	p := NewParser("", tokens)
 
 	if p == nil {
 		t.Fatal("parser should not be nil")
@@ -32,7 +34,7 @@ func TestNewParser(t *testing.T) {
 func BenchmarkNewParser(b *testing.B) {
 	tokens := make([]Token, 0)
 	for i := 0; i < b.N; i++ {
-		_ = NewParser(tokens)
+		_ = NewParser("", tokens)
 	}
 }
 
@@ -66,14 +68,19 @@ func GetTokenTestData() map[string]TokenTestData {
 							BinaryAddition,
 							&NumberNode{
 								1,
+								0, 0,
 							},
 							&NumberNode{
 								2,
+								0, 0,
 							},
+							0, 0,
 						},
 						false,
+						0, 0,
 					},
 				},
+				0, 0,
 			},
 		},
 		"assignment": {
@@ -90,10 +97,13 @@ func GetTokenTestData() map[string]TokenTestData {
 						&StringNode{
 							"Hello world!",
 							"\"Hello world!\"",
+							0, 0,
 						},
 						false,
+						0, 0,
 					},
 				},
+				0, 0,
 			},
 		},
 		"declaration": {
@@ -113,14 +123,19 @@ func GetTokenTestData() map[string]TokenTestData {
 							BinaryAddition,
 							&NumberNode{
 								1,
+								0, 0,
 							},
 							&ReferenceNode{
 								"b",
+								0, 0,
 							},
+							0, 0,
 						},
 						true,
+						0, 0,
 					},
 				},
+				0, 0,
 			},
 		},
 		// (2 + 1) * 5 + 3 / (6 - 2) - 10 / 2
@@ -167,30 +182,63 @@ func GetTokenTestData() map[string]TokenTestData {
 									BinaryMultiplication,
 									&BinaryNode{
 										BinaryAddition,
-										&NumberNode{2},
+										&NumberNode{
-										&NumberNode{1},
+											2,
+											0, 0,
 										},
-									&NumberNode{5},
+										&NumberNode{
+											1,
+											0, 0,
+										},
+										0, 0,
+									},
+									&NumberNode{
+										5,
+										0, 0,
+									},
+									0, 0,
 								},
 								&BinaryNode{
 									BinaryDivision,
-									&NumberNode{3},
+									&NumberNode{
+										3,
+										0, 0,
+									},
 									&BinaryNode{
 										BinarySubtraction,
-										&NumberNode{6},
+										&NumberNode{
-										&NumberNode{2},
+											6,
+											0, 0,
 										},
+										&NumberNode{
+											2,
+											0, 0,
 										},
+										0, 0,
+									},
+									0, 0,
+								},
+								0, 0,
 							},
 							&BinaryNode{
 								BinaryDivision,
-								&NumberNode{10},
+								&NumberNode{
-								&NumberNode{2},
+									10,
+									0, 0,
 								},
+								&NumberNode{
+									2,
+									0, 0,
+								},
+								0, 0,
+							},
+							0, 0,
 						},
 						false,
+						0, 0,
 					},
 				},
+				0, 0,
 			},
 		},
 		"condition_equal": {
@@ -210,14 +258,19 @@ func GetTokenTestData() map[string]TokenTestData {
 							BinaryEquality,
 							&NumberNode{
 								20,
+								0, 0,
 							},
 							&NumberNode{
 								15,
+								0, 0,
 							},
+							0, 0,
 						},
 						false,
+						0, 0,
 					},
 				},
+				0, 0,
 			},
 		},
 		"if_statement": {
@@ -240,10 +293,13 @@ func GetTokenTestData() map[string]TokenTestData {
 							BinaryEquality,
 							&ReferenceNode{
 								"a",
+								0, 0,
 							},
 							&NumberNode{
 								0,
+								0, 0,
 							},
+							0, 0,
 						},
 						do: &BlockNode{
 							[]Node{
@@ -251,13 +307,17 @@ func GetTokenTestData() map[string]TokenTestData {
 									"b",
 									&NumberNode{
 										1,
+										0, 0,
 									},
 									false,
+									0, 0,
+								},
+							},
+							0, 0,
 						},
 					},
 				},
-					},
+				0, 0,
-				},
 			},
 		},
 		"if_else_statement": {
@@ -286,10 +346,13 @@ func GetTokenTestData() map[string]TokenTestData {
 							BinaryEquality,
 							&ReferenceNode{
 								"a",
+								0, 0,
 							},
 							&NumberNode{
 								0,
+								0, 0,
 							},
+							0, 0,
 						},
 						do: &BlockNode{
 							[]Node{
@@ -297,10 +360,13 @@ func GetTokenTestData() map[string]TokenTestData {
 									"b",
 									&NumberNode{
 										1,
+										0, 0,
 									},
 									false,
+									0, 0,
 								},
 							},
+							0, 0,
 						},
 						otherwise: &BlockNode{
 							[]Node{
@@ -308,13 +374,17 @@ func GetTokenTestData() map[string]TokenTestData {
 									"b",
 									&NumberNode{
 										0,
+										0, 0,
 									},
 									false,
+									0, 0,
+								},
+							},
+							0, 0,
 						},
 					},
 				},
-					},
+				0, 0,
-				},
 			},
 		},
 		"empty_block": {
@@ -327,8 +397,10 @@ func GetTokenTestData() map[string]TokenTestData {
 				[]Node{
 					&BlockNode{
 						[]Node{},
+						0, 0,
 					},
 				},
+				0, 0,
 			},
 		},
 		"lambda": { // a := func(a, b) { return a + b }
@@ -338,9 +410,14 @@ func GetTokenTestData() map[string]TokenTestData {
 				NewToken(TokenFunc, 3, 4, 0, "func"),
 				NewToken(TokenOpenParenthesis, 7, 1, 0, "("),
 				NewToken(TokenName, 8, 1, 0, "a"),
+				NewToken(TokenColon, 9, 1, 0, ":"),
+				NewToken(TokenName, 10, 5, 0, "number"),
 				NewToken(TokenComma, 9, 1, 0, ","),
 				NewToken(TokenName, 10, 1, 0, "b"),
+				NewToken(TokenColon, 9, 1, 0, ":"),
+				NewToken(TokenName, 10, 5, 0, "number"),
 				NewToken(TokenCloseParenthesis, 11, 1, 0, ")"),
+				NewToken(TokenName, 10, 5, 0, "number"),
 
 				NewToken(TokenOpenBrace, 12, 1, 1, "{"),
 				NewToken(TokenReturn, 13, 6, 1, "return"),
@@ -357,7 +434,17 @@ func GetTokenTestData() map[string]TokenTestData {
 						"a",
 						&FunctionNode{
 							"*",
-							[]string{"a", "b"},
+							[]FunctionParameter{
+								{
+									"a",
+									&NumberSignature{},
+								},
+								{
+									"b",
+									&NumberSignature{},
+								},
+							},
+							&NumberSignature{},
 							&BlockNode{
 								[]Node{
 									&ReturnNode{
@@ -365,18 +452,26 @@ func GetTokenTestData() map[string]TokenTestData {
 											BinaryAddition,
 											&ReferenceNode{
 												"a",
+												0, 0,
 											},
 											&ReferenceNode{
 												"b",
+												0, 0,
+											},
+											0, 0,
+										},
+										0, 0,
 									},
 								},
+								0, 0,
 							},
-								},
+							0, 0,
-							},
 						},
 						true,
+						0, 0,
 					},
 				},
+				0, 0,
 			},
 		},
 		"function_declaration": {
@@ -404,7 +499,17 @@ func GetTokenTestData() map[string]TokenTestData {
 						"a",
 						&FunctionNode{
 							"a",
-							[]string{"a", "b"},
+							[]FunctionParameter{
+								{
+									"a",
+									&NumberSignature{},
+								},
+								{
+									"b",
+									&NumberSignature{},
+								},
+							},
+							&NumberSignature{},
 							&BlockNode{
 								[]Node{
 									&ReturnNode{
@@ -412,18 +517,26 @@ func GetTokenTestData() map[string]TokenTestData {
 											BinaryAddition,
 											&ReferenceNode{
 												"a",
+												0, 0,
 											},
 											&ReferenceNode{
 												"b",
+												0, 0,
+											},
+											0, 0,
+										},
+										0, 0,
 									},
 								},
+								0, 0,
 							},
-								},
+							0, 0,
-							},
 						},
 						true,
+						0, 0,
 					},
 				},
+				0, 0,
 			},
 		},
 		"prop_getting": {
@@ -443,12 +556,16 @@ func GetTokenTestData() map[string]TokenTestData {
 						&AccessNode{
 							&ReferenceNode{
 								"a",
+								0, 0,
 							},
 							"b",
+							0, 0,
 						},
 						true,
+						0, 0,
 					},
 				},
+				0, 0,
 			},
 		},
 		"list_init": {
@@ -488,27 +605,43 @@ func GetTokenTestData() map[string]TokenTestData {
 							[]Node{
 								&ReferenceNode{
 									"a",
+									0, 0,
 								},
 								&NumberNode{
 									3.141,
+									0, 0,
 								},
 								&StringNode{
 									"Hello world!",
 									"\"Hello world!\"",
+									0, 0,
 								},
 								&BooleanNode{
 									true,
+									0, 0,
 								},
 								&ListNode{
 									[]Node{
-										&NumberNode{2}, &NumberNode{3},
+										&NumberNode{
+											2,
+											0, 0,
+										}, &NumberNode{
+											3,
+											0, 0,
 										},
 									},
+									nil,
+									0, 0,
 								},
 							},
+							nil,
+							0, 0,
+						},
 						true,
+						0, 0,
 					},
 				},
+				0, 0,
 			},
 		},
 	}
@@ -642,15 +775,17 @@ func NodeEquality(t *testing.T, n1 Node, n2 Node) {
 			t.Logf("Function node names match (%s)", n.name)
 		}
 
-		if len(n.params) != len(m.params) {
+		if len(n.parameters) != len(m.parameters) {
-			t.Fatalf("Function node parameters count does not match (%d and %d)", len(n.params), len(m.params))
+			t.Fatalf("Function node parameters count does not match (%d and %d)", len(n.parameters), len(m.parameters))
 		} else {
-			t.Logf("Function node parameters count is equal (%d) ", len(n.params))
+			t.Logf("Function node parameters count is equal (%d) ", len(n.parameters))
 		}
 
-		for i, p := range m.params {
+		for i, p := range m.parameters {
-			if n.params[i] != p {
+			if !n.parameters[i].Signature.Matches(p.Signature) {
-				t.Errorf("Function node parameter %d does not match: %s and %s", i, p, m.params)
+				t.Errorf("Function node parameter signature %d does not match: %s and %s", i, p.Signature, n.parameters[i].Signature)
+			} else if n.parameters[i].Name != p.Name {
+				t.Errorf("Function node parameter name %d does not match: %s and %s", i, p.Name, n.parameters[i].Name)
 			} else {
 				t.Logf("Function node parameter %d matches (%s)", i, p)
 			}
@@ -665,6 +800,105 @@ func NodeEquality(t *testing.T, n1 Node, n2 Node) {
 	}
 }
 
+func SerializeTokens(tokens []Token) string {
+	out := strings.Builder{}
+	level := 0
+
+	for _, token := range tokens {
+		switch token.Type {
+		case TokenPlus:
+			out.WriteString(" + ")
+		case TokenMinus:
+			out.WriteString(" - ")
+		case TokenStar:
+			out.WriteString("*")
+		case TokenSlash:
+			out.WriteString("/")
+		case TokenBang:
+			out.WriteString("!")
+		case TokenSemicolon:
+			out.WriteString(";")
+		case TokenNumber:
+			out.WriteString(token.Lexeme)
+		case TokenString:
+			out.WriteString(fmt.Sprintf("\"%s\"", token.Lexeme))
+		case TokenName:
+			out.WriteString(token.Lexeme)
+		case TokenOpenParenthesis:
+			out.WriteString("(")
+		case TokenCloseParenthesis:
+			out.WriteString(")")
+		case TokenOpenBracket:
+			out.WriteString("[")
+		case TokenCloseBracket:
+			out.WriteString("]")
+		case TokenOpenBrace:
+			out.WriteString("{")
+			level = level + 1
+		case TokenCloseBrace:
+			out.WriteString("}")
+			level = level - 1
+		case TokenTrue:
+			out.WriteString("true")
+		case TokenFalse:
+			out.WriteString("false")
+		case TokenNil:
+			out.WriteString("nil")
+		case TokenFunc:
+			out.WriteString("func")
+		case TokenReturn:
+			out.WriteString("return ")
+		case TokenWhile:
+			out.WriteString("while ")
+		case TokenVar:
+			out.WriteString("var ")
+		case TokenIf:
+			out.WriteString("if ")
+		case TokenElse:
+			out.WriteString(" else ")
+		case TokenImport:
+			out.WriteString("import ")
+		case TokenComma:
+			out.WriteString(", ")
+		case TokenDot:
+			out.WriteString(".")
+		case TokenColon:
+			out.WriteString(": ")
+		case TokenAssign:
+			out.WriteString(" = ")
+		case TokenDeclare:
+			out.WriteString(" := ")
+		case TokenBangEquals:
+			out.WriteString(" != ")
+		case TokenEquals:
+			out.WriteString(" == ")
+		case TokenGreaterThan:
+			out.WriteString(" > ")
+		case TokenLessThan:
+			out.WriteString(" < ")
+		case TokenGreaterThanOrEqual:
+			out.WriteString(" >= ")
+		case TokenLessThanOrEqual:
+			out.WriteString(" <= ")
+		case TokenDoubleAmpersand:
+			out.WriteString(" && ")
+		case TokenDoublePipe:
+			out.WriteString(" || ")
+		case TokenBreakpoint:
+			out.WriteString("breakpoint")
+		case TokenEOF:
+			out.WriteString(fmt.Sprintf("<error: \"%s\">", token.Lexeme))
+		case TokenHexadecimal:
+			out.WriteString(token.Lexeme)
+		case TokenPipe:
+			out.WriteString(" | ")
+		case TokenError:
+		}
+	}
+
+	return out.String()
+}
+
 func TestParser_Parse(t *testing.T) {
 	t.Logf("Getting test data")
 	tokenData := GetTokenTestData()
@@ -676,17 +910,17 @@ func TestParser_Parse(t *testing.T) {
 
 		t.Run(name, func(t *testing.T) {
 			t.Logf("Initializing parser")
-			p := NewParser(data.tokens)
+			p := NewParser("", data.tokens)
 
 			t.Logf("Parsing main")
-			tree, err := p.Parse()
+			tree, err := p.Parse("")
 
 			if err != nil {
-				t.Fatalf("Unexpected error(s): %s", err.(*ParsingError).Format([]rune{}))
+				t.Fatalf("Unexpected error(s): %s", err.(ParsingError).Format())
 			}
 
 			t.Logf("Checking parsed tree")
-			NodeEquality(t, tree, data.tree)
+			NodeEquality(t, tree.Block, data.tree)
 		})
 	}
 }
@@ -697,9 +931,9 @@ func BenchmarkParser_Parse(b *testing.B) {
 	for name, data := range tokenData {
 		b.Run(name, func(b *testing.B) {
 			for i := 0; i < b.N; i++ {
-				p := NewParser(data.tokens)
+				p := NewParser("", data.tokens)
 
-				_, _ = p.Parse()
+				_, _ = p.Parse("")
 			}
 		})
 	}

core/stack.go

@@ -2,24 +2,27 @@ package core
 
 type Stack[T any] struct {
 	Current  Pos
-	Size    Pos
+	Capacity Pos
 
 	items []T
 }
 
-func NewStack[T any](size Pos) *Stack[T] {
+func NewStack[T any](capacity Pos) *Stack[T] {
 	return &Stack[T]{
-		items:   make([]T, size),
+		items:    make([]T, 16),
-		Size:    size,
+		Capacity: capacity,
 		Current:  0,
 	}
 }
 
 func (s *Stack[T]) Push(items ...T) {
 	for _, item := range items {
-		if s.Current >= s.Size {
+		if s.Current >= s.Capacity {
 			panic("stack overflow")
 		}
+		if int(s.Current) == len(s.items) {
+			s.items = append(s.items, item)
+		}
 
 		s.items[s.Current] = item
 		s.Current++
@@ -45,7 +48,7 @@ func (s *Stack[T]) Peek() T {
 
 // check whether the stack is invalid (stack over-/underflow)
 func (s *Stack[T]) check() {
-	if s.Current >= s.Size {
+	if s.Current >= s.Capacity {
 		panic("stack underflow")
 	}
 

core/stack_test.go

@@ -25,16 +25,10 @@ func TestNewStack(t *testing.T) {
 
 	s := NewStack[any](Pos(size))
 
-	if s.Size != Pos(size) {
+	if s.Capacity != Pos(size) {
-		t.Errorf("Stack size (%d) does not match expected size (%d)", s.Size, size)
+		t.Errorf("Stack size (%d) does not match expected size (%d)", s.Capacity, size)
 	} else {
-		t.Logf("Stack size is expected size (%d)", s.Size)
+		t.Logf("Stack size is expected size (%d)", s.Capacity)
-	}
-
-	if len(s.items) != size {
-		t.Errorf("internal items slice size (%d) does not match expected size (%d)", len(s.items), size)
-	} else {
-		t.Logf("internal items slice size is as expected (%d)", len(s.items))
 	}
 
 	if s.Current != 0 {

core/types.go

@@ -0,0 +1,349 @@
+package core
+
+import (
+	"fmt"
+	"strings"
+)
+
+type Type int
+
+const (
+	TypeString Type = iota
+	TypeNumber
+	TypeBoolean
+	TypeNil
+	TypeList
+	TypeObject
+	TypeFunction
+	TypeAny
+	TypeComposite
+	TypeInner
+)
+
+func (t Type) String() string {
+	switch t {
+	case TypeString:
+		return "string"
+	case TypeNumber:
+		return "number"
+	case TypeBoolean:
+		return "boolean"
+	case TypeNil:
+		return "nil"
+	case TypeList:
+		return "list"
+	case TypeObject:
+		return "object"
+	case TypeFunction:
+		return "func"
+	case TypeAny:
+		return "any"
+	case TypeComposite:
+		return "composite"
+	case TypeInner:
+		return "inner"
+	}
+
+	panic(fmt.Sprintf("unsupported string conversion for type %v", int(t)))
+}
+
+func SignatureOf(v Value) TypeSignature {
+	switch t := v.(type) {
+	case *StringValue:
+		return &StringSignature{}
+	case *NumberValue:
+		return &NumberSignature{}
+	case *BoolValue:
+		return &BooleanSignature{}
+	case *ListValue:
+		// try to deduce contents type
+		var contains TypeSignature
+
+		for _, p := range t.Items {
+			sig := SignatureOf(p)
+			if contains == nil {
+				contains = sig
+			} else if !contains.Matches(sig) {
+				contains = &AnySignature{}
+				break
+			}
+		}
+
+		return &ListSignature{
+			contains,
+		}
+	case *ObjectValue:
+		return &ObjectSignature{}
+	case *FunctionValue:
+		params := make([]TypeSignature, len(t.Params))
+
+		for i, p := range t.Params {
+			params[i] = p.Signature
+		}
+
+		return &FunctionSignature{
+			params,
+			t.Yield,
+		}
+	case *BuiltinFunctionValue:
+		return t.Signature
+	}
+
+	panic(fmt.Sprintf("unknown value; cannot get signature of %s", v))
+}
+
+type TypeSignature interface {
+	Type() Type
+
+	// Matches check if this type signature matches another.
+	Matches(TypeSignature) bool
+
+	// String create a human-readable string version of the value type.
+	String() string
+}
+
+type NilSignature struct{}
+
+func (*NilSignature) Type() Type {
+	return TypeNil
+}
+
+func (s *NilSignature) Matches(other TypeSignature) bool {
+	if other.Type() == TypeComposite {
+		return other.Matches(s)
+	}
+
+	return other.Type() == TypeAny || other.Type() == TypeNil
+}
+
+func (*NilSignature) String() string {
+	return "nil"
+}
+
+type StringSignature struct{}
+
+func (*StringSignature) Type() Type {
+	return TypeString
+}
+
+func (s *StringSignature) Matches(other TypeSignature) bool {
+	if other.Type() == TypeComposite {
+		return other.Matches(s)
+	}
+
+	return other.Type() == TypeAny || other.Type() == TypeString
+}
+
+func (*StringSignature) String() string {
+	return "string"
+}
+
+type NumberSignature struct{}
+
+func (*NumberSignature) Type() Type {
+	return TypeNumber
+}
+
+func (s *NumberSignature) Matches(other TypeSignature) bool {
+	if other.Type() == TypeComposite {
+		return other.Matches(s)
+	}
+
+	return other.Type() == TypeAny || other.Type() == TypeNumber
+}
+
+func (*NumberSignature) String() string {
+	return "number"
+}
+
+type BooleanSignature struct{}
+
+func (*BooleanSignature) Type() Type {
+	return TypeBoolean
+}
+
+func (s *BooleanSignature) Matches(other TypeSignature) bool {
+	if other.Type() == TypeComposite {
+		return other.Matches(s)
+	}
+
+	return other.Type() == TypeAny || other.Type() == TypeBoolean
+}
+
+func (*BooleanSignature) String() string {
+	return "boolean"
+}
+
+type ListSignature struct {
+	Contents TypeSignature
+}
+
+func (*ListSignature) Type() Type {
+	return TypeList
+}
+
+func (s *ListSignature) Matches(other TypeSignature) bool {
+	if other.Type() == TypeComposite {
+		return other.Matches(s)
+	}
+
+	return other.Type() == TypeAny || (other.Type() == TypeList && other.(*ListSignature).Contents.Matches(s.Contents))
+}
+
+func (s *ListSignature) String() string {
+	return fmt.Sprintf("list[%s]", s.Contents)
+}
+
+type ObjectSignature struct {
+	Members map[string]TypeSignature
+}
+
+func (*ObjectSignature) Type() Type {
+	return TypeObject
+}
+
+func (s *ObjectSignature) Matches(other TypeSignature) bool {
+	if other.Type() == TypeComposite {
+		return other.Matches(s)
+	}
+
+	if other.Type() == TypeAny {
+		return true
+	}
+
+	if other.Type() != TypeObject {
+		return false
+	}
+
+	o := other.(*ObjectSignature)
+
+	if len(o.Members) != len(s.Members) {
+		return false
+	}
+
+	for name, member := range s.Members {
+		v, ok := o.Members[name]
+
+		if !ok {
+			return false
+		}
+
+		if !v.Matches(member) {
+			return false
+		}
+	}
+
+	return true
+}
+
+func (s *ObjectSignature) String() string {
+	panic("unimplemented")
+}
+
+type FunctionSignature struct {
+	In  []TypeSignature
+	Out TypeSignature
+}
+
+func (*FunctionSignature) Type() Type {
+	return TypeFunction
+}
+
+func (s *FunctionSignature) Matches(other TypeSignature) bool {
+	if other.Type() == TypeComposite {
+		return other.Matches(s)
+	}
+
+	if other.Type() == TypeAny {
+		return true
+	}
+
+	if other.Type() != TypeFunction {
+		return false
+	}
+
+	f := other.(*FunctionSignature)
+
+	if !s.Out.Matches(f.Out) {
+		return false
+	}
+
+	if len(f.In) != len(s.In) {
+		return false
+	}
+
+	for i, p := range s.In {
+		v := f.In[i]
+		if !p.Matches(v) {
+			return false
+		}
+	}
+
+	return true
+}
+
+func (s *FunctionSignature) String() string {
+	b := strings.Builder{}
+
+	b.WriteString("func(")
+
+	for i, t := range s.In {
+		if i > 0 {
+			b.WriteString(", ")
+		}
+		b.WriteString(t.String())
+	}
+
+	b.WriteString(")")
+	if s.Out.Type() != TypeNil {
+		b.WriteString(" ")
+		b.WriteString(s.Out.String())
+	}
+
+	return b.String()
+}
+
+type AnySignature struct{}
+
+func (*AnySignature) Type() Type {
+	return TypeAny
+}
+
+func (*AnySignature) Matches(_ TypeSignature) bool {
+	return true
+}
+
+func (*AnySignature) String() string {
+	return "any"
+}
+
+type CompositeSignature struct {
+	A TypeSignature
+	B TypeSignature
+}
+
+func (*CompositeSignature) Type() Type {
+	return TypeComposite
+}
+
+func (s *CompositeSignature) Matches(other TypeSignature) bool {
+	return s.A.Matches(other) || s.B.Matches(other)
+}
+
+func (s *CompositeSignature) String() string {
+	return fmt.Sprintf("%s|%s", s.A, s.B)
+}
+
+type InnerSignature struct{}
+
+func (*InnerSignature) Type() Type {
+	return TypeInner
+}
+
+func (*InnerSignature) Matches(_ TypeSignature) bool {
+	return false
+}
+
+func (*InnerSignature) String() string {
+	return "inner"
+}

core/values.go

@@ -68,15 +68,6 @@ func GoToValue(gov interface{}) Value {
 		return &StringValue{
 			v,
 		}
-	case []interface{}:
-		values := make([]Value, len(v))
-		for i, value := range v {
-			values[i] = GoToValue(value)
-		}
-
-		return &ListValue{
-			values,
-		}
 	case map[string]interface{}:
 		values := map[string]Value{}
 		for key, value := range v {
@@ -86,9 +77,17 @@ func GoToValue(gov interface{}) Value {
 		return &ObjectValue{
 			values,
 		}
+	case Value:
+		return v
+	default:
+		if reflect.TypeOf(v).Kind() == reflect.Slice {
+			return &ListValue{
+				v.([]Value),
+			}
+		}
 	}
 
-	panic(fmt.Sprintf("unsupported automatic type conversion: %v (%s)", gov, reflect.TypeOf(gov).Name()))
+	panic(fmt.Sprintf("unsupported automatic type conversion: %v (%s)", gov, reflect.TypeOf(gov)))
 }
 
 type Value interface {
@@ -106,6 +105,9 @@ type Value interface {
 
 	// Get a member from the value. An error is returned if the member does not exist
 	Get(string) (Value, error)
+
+	// Clone create a clone of the value. The returned value is a pointer to a new value of the same type as the value.
+	Clone() Value
 }
 
 type NilValue struct{}
@@ -130,8 +132,12 @@ func (v *NilValue) Get(_ string) (Value, error) {
 	return nil, errors.New("nil has no properties")
 }
 
+func (v *NilValue) Clone() Value {
+	return &NilValue{}
+}
+
 type BoolValue struct {
-	bool
+	Boolean bool
 }
 
 func (v *BoolValue) Type() ValueType {
@@ -139,7 +145,7 @@ func (v *BoolValue) Type() ValueType {
 }
 
 func (v *BoolValue) String() string {
-	if v.bool {
+	if v.Boolean {
 		return "true"
 	} else {
 		return "false"
@@ -151,16 +157,22 @@ func (v *BoolValue) DebugString() string {
 }
 
 func (v *BoolValue) Equals(other Value) bool {
-	return other.Type() == BoolValueType && other.(*BoolValue).bool == v.bool
+	return other.Type() == BoolValueType && other.(*BoolValue).Boolean == v.Boolean
 }
 
 func (v *BoolValue) Get(_ string) (Value, error) {
 	return nil, errors.New("booleans have no properties")
 }
 
+func (v *BoolValue) Clone() Value {
+	return &BoolValue{
+		v.Boolean,
+	}
+}
+
 // ObjectValue An object with any number of members (key-value pairs)
 type ObjectValue struct {
-	members map[string]Value
+	Members map[string]Value
 }
 
 func (v *ObjectValue) Type() ValueType {
@@ -169,12 +181,12 @@ func (v *ObjectValue) Type() ValueType {
 
 func (v *ObjectValue) String() string {
 	out := "{"
-	for key, value := range v.members {
+	for key, value := range v.Members {
 		if out != "{" {
 			out += ", "
 		}
 
-		out += fmt.Sprintf("%q=%s", key, value.String())
+		out += fmt.Sprintf("%q=%s", key, value.DebugString())
 	}
 	out += "}"
 
@@ -191,8 +203,8 @@ func (v *ObjectValue) Equals(other Value) bool {
 		return false
 	}
 
-	for key, value := range v.members {
+	for key, value := range v.Members {
-		if !object.members[key].Equals(value) {
+		if !object.Members[key].Equals(value) {
 			return false
 		}
 	}
@@ -203,26 +215,30 @@ func (v *ObjectValue) Equals(other Value) bool {
 var ObjectPrototype = map[string]Value{
 	"set": &BuiltinFunctionValue{
 		"set",
-		[]string{"property", "value"},
+		&FunctionSignature{
-		func(vm *VM, _this Value, params map[string]Value) (Value, error) {
+			[]TypeSignature{&StringSignature{}, &ListSignature{}},
+			&NilSignature{},
+		},
+		func(vm *VM, _this Value, params []Value) (Value, error) {
 			this := _this.(*ObjectValue)
 
-			p := params["property"]
+			p := params[1]
-			v, ok := params["value"].(*StringValue)
+			v, ok := params[0].(*StringValue)
 			if !ok {
 				return nil, errors.New("property is not a string")
 			}
 
-			this.members[v.string] = p
+			this.Members[v.Text] = p
 
 			return &NilValue{}, nil
 		},
 		nil,
+		false,
 	},
 }
 
 func (v *ObjectValue) Get(key string) (Value, error) {
-	if member, ok := v.members[key]; ok {
+	if member, ok := v.Members[key]; ok {
 		return member, nil
 	} else if p, ok := ObjectPrototype[key]; ok {
 		return p, nil
@@ -231,9 +247,21 @@ func (v *ObjectValue) Get(key string) (Value, error) {
 	}
 }
 
+func (v *ObjectValue) Clone() Value {
+	m := make(map[string]Value, len(v.Members))
+
+	for name, mem := range v.Members {
+		m[name] = mem.Clone()
+	}
+
+	return &ObjectValue{
+		m,
+	}
+}
+
 // NumberValue Integer or floating-point values
 type NumberValue struct {
-	float64
+	Number float64
 }
 
 const NumberSize int = 64
@@ -243,7 +271,7 @@ func (v *NumberValue) Type() ValueType {
 }
 
 func (v *NumberValue) String() string {
-	return strconv.FormatFloat(v.float64, 'g', -1, NumberSize)
+	return strconv.FormatFloat(v.Number, 'g', -1, NumberSize)
 }
 
 func (v *NumberValue) DebugString() string {
@@ -251,7 +279,7 @@ func (v *NumberValue) DebugString() string {
 }
 
 func (v *NumberValue) Equals(other Value) bool {
-	return other.Type() == NumberValueType && other.(*NumberValue).float64 == v.float64
+	return other.Type() == NumberValueType && other.(*NumberValue).Number == v.Number
 }
 
 func (v *NumberValue) Get(_ string) (Value, error) {
@@ -259,8 +287,14 @@ func (v *NumberValue) Get(_ string) (Value, error) {
 	return nil, errors.New("numbers have no properties")
 }
 
+func (v *NumberValue) Clone() Value {
+	return &NumberValue{
+		v.Number,
+	}
+}
+
 type StringValue struct {
-	string
+	Text string
 }
 
 func (v *StringValue) Type() ValueType {
@@ -268,7 +302,7 @@ func (v *StringValue) Type() ValueType {
 }
 
 func (v *StringValue) String() string {
-	return v.string
+	return v.Text
 }
 
 func (v *StringValue) DebugString() string {
@@ -276,31 +310,47 @@ func (v *StringValue) DebugString() string {
 }
 
 func (v *StringValue) Equals(other Value) bool {
-	return other.Type() == StringValueType && other.(*StringValue).string == v.string
+	return other.Type() == StringValueType && other.(*StringValue).Text == v.Text
 }
 
 var StringPrototype = map[string]*BuiltinFunctionValue{
 	"split": {
 		"split",
-		[]string{"seperator"},
+		&FunctionSignature{
-		func(vm *VM, this Value, m map[string]Value) (Value, error) {
+			[]TypeSignature{&StringSignature{}},
+			&ListSignature{
+				&StringSignature{},
+			},
+		},
+		func(vm *VM, this Value, v []Value) (Value, error) {
 			str := this.(*StringValue).String()
-			sep := m["seperator"].(*StringValue).String()
+			sep := v[0].(*StringValue).String()
 
-			var out []string
+			var out []Value
 			tmp := strings.Builder{}
 			for i := 0; i < len(str)-len(sep); i++ {
 				tmp.WriteRune([]rune(str)[i])
 
 				if str[i:i+len(sep)] == sep {
-					out = append(out, tmp.String())
+					out = append(out, &StringValue{tmp.String()})
 					tmp.Reset()
 				}
 			}
 
-			return GoToValue(out), nil
+			return &ListValue{out}, nil
 		},
 		nil,
+		true,
+	},
+	"length": {
+		Name: "length",
+		Signature: &FunctionSignature{
+			[]TypeSignature{},
+			&NumberSignature{},
+		},
+		F: func(vm *VM, this Value, _ []Value) (Value, error) {
+			return GoToValue(len(this.(*StringValue).Text)), nil
+		},
 	},
 }
 
@@ -312,9 +362,15 @@ func (v *StringValue) Get(key string) (Value, error) {
 	return nil, errors.New(fmt.Sprintf("string has no property \"%s\"", key))
 }
 
+func (v *StringValue) Clone() Value {
+	return &StringValue{
+		v.Text,
+	}
+}
+
 // ListValue a dynamic list of values
 type ListValue struct {
-	items []Value
+	Items []Value
 }
 
 func (v *ListValue) Type() ValueType {
@@ -323,7 +379,7 @@ func (v *ListValue) Type() ValueType {
 
 func (v *ListValue) String() string {
 	out := "["
-	for i, item := range v.items {
+	for i, item := range v.Items {
 		if i != 0 {
 			out += ", "
 		}
@@ -345,12 +401,12 @@ func (v *ListValue) Equals(other Value) bool {
 
 	l := other.(*ListValue)
 
-	if len(v.items) != len(l.items) {
+	if len(v.Items) != len(l.Items) {
 		return false
 	}
 
-	for i, item := range l.items {
+	for i, item := range v.Items {
-		if !item.Equals(l.items[i]) {
+		if !item.Equals(l.Items[i]) {
 			return false
 		}
 	}
@@ -361,19 +417,28 @@ func (v *ListValue) Equals(other Value) bool {
 var ListPrototype = map[string]*BuiltinFunctionValue{
 	"append": {
 		"append",
-		[]string{"item"},
+		&FunctionSignature{
-		func(_ *VM, this Value, p map[string]Value) (Value, error) {
+			[]TypeSignature{&AnySignature{}},
-			this.(*ListValue).items = append(this.(*ListValue).items, p["item"])
+			&NilSignature{},
+		},
+		func(_ *VM, this Value, v []Value) (Value, error) {
+			this.(*ListValue).Items = append(this.(*ListValue).Items, v[0])
 			return &NilValue{}, nil
 		},
 		nil,
+		false,
 	},
 	"at": {
 		"at",
-		[]string{"index"},
+		&FunctionSignature{
-		func(_ *VM, this Value, p map[string]Value) (Value, error) {
+			[]TypeSignature{
-			items := this.(*ListValue).items
+				&NumberSignature{},
-			index := int(p["index"].(*NumberValue).float64)
+			},
+			&InnerSignature{},
+		},
+		func(_ *VM, this Value, p []Value) (Value, error) {
+			items := this.(*ListValue).Items
+			index := int(p[0].(*NumberValue).Number)
 
 			if index >= len(items) {
 				return nil, errors.New(fmt.Sprintf("list index %x out of range", index))
@@ -382,56 +447,41 @@ var ListPrototype = map[string]*BuiltinFunctionValue{
 			return items[index], nil
 		},
 		nil,
+		false,
 	},
 	"length": {
 		"length",
-		[]string{},
+		&FunctionSignature{
-		func(_ *VM, this Value, p map[string]Value) (Value, error) {
+			[]TypeSignature{},
-			return GoToValue(len(this.(*ListValue).items)), nil
+			&NumberSignature{},
-		},
+		},
-		nil,
+		func(_ *VM, this Value, _ []Value) (Value, error) {
-	},
+			return GoToValue(len(this.(*ListValue).Items)), nil
-	"map": {
-		"map",
-		[]string{"f"},
-		func(vm *VM, value Value, m map[string]Value) (Value, error) {
-			list := value.(*ListValue)
-
-			v := m["f"]
-			var f Value
-			f, ok := v.(*FunctionValue)
-			if !ok {
-				f, ok = v.(*BuiltinFunctionValue)
-
-				if !ok {
-					return nil, errors.New(fmt.Sprintf("not a function to apply: %s", v))
-				}
-			}
-
-			for i, item := range list.items {
-				var err error
-				list.items[i], err = vm.Call(f, []Value{
-					item,
-				})
-
-				if err != nil {
-					return nil, err
-				}
-			}
-
-			return list, nil
 		},
 		nil,
+		false,
 	},
 	"reduce": {
 		"reduce",
-		[]string{"f", "start"},
+		&FunctionSignature{
-		func(vm *VM, value Value, m map[string]Value) (Value, error) {
+			[]TypeSignature{
+				&FunctionSignature{
+					[]TypeSignature{
+						&AnySignature{},
+						&AnySignature{},
+					},
+					&AnySignature{},
+				},
+				&AnySignature{},
+			},
+			&AnySignature{},
+		},
+		func(vm *VM, value Value, m []Value) (Value, error) {
 			list := value.(*ListValue)
-			f := m["f"]
+			f := m[0]
-			sum := m["start"]
+			sum := m[1]
 
-			for _, v := range list.items {
+			for _, v := range list.Items {
 				result, err := vm.Call(f, []Value{sum, v})
 				if err != nil {
 					return nil, err
@@ -442,6 +492,7 @@ var ListPrototype = map[string]*BuiltinFunctionValue{
 			return sum, nil
 		},
 		nil,
+		false,
 	},
 }
 
@@ -453,9 +504,22 @@ func (v *ListValue) Get(key string) (Value, error) {
 	return nil, errors.New(fmt.Sprintf("list has no property \"%s\"", key))
 }
 
+func (v *ListValue) Clone() Value {
+	n := make([]Value, len(v.Items))
+
+	for i, item := range v.Items {
+		n[i] = item.Clone()
+	}
+
+	return &ListValue{
+		n,
+	}
+}
+
 type FunctionValue struct {
 	Name   string
-	Params []string
+	Params []FunctionParameter
+	Yield  TypeSignature
 	Chunk  *Chunk
 	Parent Value
 }
@@ -482,11 +546,22 @@ func (v *FunctionValue) Get(_ string) (Value, error) {
 	return nil, errors.New("functions have no properties")
 }
 
+func (v *FunctionValue) Clone() Value {
+	return &FunctionValue{
+		v.Name,
+		v.Params,
+		v.Yield,
+		v.Chunk,
+		v.Parent,
+	}
+}
+
 type BuiltinFunctionValue struct {
 	Name      string
-	Parameters []string
+	Signature *FunctionSignature
-	F          func(*VM, Value, map[string]Value) (Value, error)
+	F         func(*VM, Value, []Value) (Value, error)
 	Parent    Value
+	Constant  bool
 }
 
 func (v *BuiltinFunctionValue) Type() ValueType {
@@ -510,6 +585,16 @@ func (v *BuiltinFunctionValue) Get(_ string) (Value, error) {
 	return nil, errors.New("functions have no properties")
 }
 
+func (v *BuiltinFunctionValue) Clone() Value {
+	return &BuiltinFunctionValue{
+		v.Name,
+		v.Signature,
+		v.F,
+		v.Parent,
+		v.Constant,
+	}
+}
+
 // VariableValue a value wrapper for variables kept on the stack
 type VariableValue struct {
 	name  string
@@ -541,3 +626,11 @@ func (v *VariableValue) Equals(other Value) bool {
 func (v *VariableValue) Get(_ string) (Value, error) {
 	return nil, errors.New("variables have no properties")
 }
+
+func (v *VariableValue) Clone() Value {
+	return &VariableValue{
+		v.name,
+		v.value.Clone(),
+		v.scope,
+	}
+}

core/values_test.go

@@ -16,19 +16,19 @@ func CompareValues(t *testing.T, got Value, want Value) {
 		t.Logf("Both are nil")
 		return
 	case BoolValueType:
-		if got.(*BoolValue).bool != want.(*BoolValue).bool {
+		if got.(*BoolValue).Boolean != want.(*BoolValue).Boolean {
 			t.Errorf("bool value mismatch: got %v, want %v", got.(*BoolValue), want.(*BoolValue))
 		} else {
 			t.Logf("Both are same boolean (%s)", want.(*BoolValue).String())
 		}
 	case NumberValueType:
-		if got.(*NumberValue).float64 != want.(*NumberValue).float64 {
+		if got.(*NumberValue).Number != want.(*NumberValue).Number {
 			t.Errorf("number value mismatch: got %v, want %v", got.(*NumberValue), want.(*NumberValue))
 		} else {
 			t.Logf("Both are same number (%s)", got.(*NumberValue).String())
 		}
 	case StringValueType:
-		if got.(*StringValue).string != want.(*StringValue).string {
+		if got.(*StringValue).Text != want.(*StringValue).Text {
 			t.Errorf("string value mismatch: got %v, want %v", got.(*StringValue), want.(*StringValue))
 		} else {
 			t.Logf("Both are same string (%s)", got.(*StringValue).String())
@@ -60,19 +60,10 @@ func CompareValues(t *testing.T, got Value, want Value) {
 			t.Errorf("builtin function name mismatch: got %v, want %v", n.Name, m.Name)
 		}
 
-		if len(n.Parameters) != len(m.Parameters) {
+		if !n.Signature.Matches(m.Signature) {
-			t.Errorf("builtin function parameter count mismatch: got %v, want %v", n.Parameters, m.Parameters)
+			t.Errorf("builtin function parameter count mismatch: got %v, want %v", n, m)
 		}
 
-		for i, v := range n.Parameters {
-			if v != m.Parameters[i] {
-				t.Errorf("builtin function parameter %d mismatch: got %v, want %v", i, v, m.Parameters[i])
-			}
-		}
-
-		if &n.F != &m.F {
-			t.Errorf("builtin function f mismatch: got %v, want %v", &n.F, &m.F)
-		}
 	case VariableValueType:
 		n := got.(*VariableValue)
 		m := want.(*VariableValue)
@@ -87,6 +78,32 @@ func CompareValues(t *testing.T, got Value, want Value) {
 
 		CompareValues(t, n.value, m.value)
 
+	case ListValueType:
+		n := got.(*ListValue)
+		m := want.(*ListValue)
+
+		if len(n.Items) != len(m.Items) {
+			t.Fatalf("list items length mismatch: got %d, want %d", len(n.Items), len(m.Items))
+		}
+
+		for i, v := range n.Items {
+			t.Logf("comparing list items #%d: got %s, want %s", i, v, m.Items[i])
+			CompareValues(t, v, m.Items[i])
+		}
+
+	case ObjectValueType:
+		n := got.(*ObjectValue)
+		m := want.(*ObjectValue)
+
+		if len(n.Members) != len(m.Members) {
+			t.Fatalf("object members count mismatch: got %d, want %d", len(n.Members), len(m.Members))
+		}
+
+		for k, v := range n.Members {
+			t.Logf("comparing object member %s: got %s, want %s", k, v, m.Members[k])
+			CompareValues(t, v, m.Members[k])
+		}
+
 	default:
 		panic("unimplemented comparison")
 	}

core/vm.go

@@ -6,6 +6,8 @@ import (
 	"errors"
 	"fmt"
 	"log"
+	"math"
+	"os"
 	"strings"
 )
 
@@ -26,6 +28,8 @@ const (
 	InstructionMul
 	// InstructionDiv pop two and divide the second by the first
 	InstructionDiv
+	// InstructionNegate negate the value; if it was positive, make it negative, and vice versa.
+	InstructionNegate
 	// InstructionEquals whether the two top values on the stack are equal
 	InstructionEquals
 	// InstructionNotEqual whether the two top values on the stack are not equal
@@ -99,6 +103,8 @@ const (
 	// items to include minus one. (value of 0 => 1 item, value of 1 => 2 items, etc.) The order is reversed compared
 	// to on the stack; the top value on the stack is the last in the list.
 	InstructionFormList
+	// InstructionConcatLists concatenate lists, producing a new list with the values of both lists. Pops two lists.
+	InstructionConcatLists
 
 	// InstructionBreakpoint for debugging purposes
 	InstructionBreakpoint
@@ -118,6 +124,8 @@ func (b Bytecode) String() string {
 		return "MUL"
 	case InstructionDiv:
 		return "DIV"
+	case InstructionNegate:
+		return "NEGATE"
 	case InstructionEquals:
 		return "EQUALS"
 	case InstructionNotEqual:
@@ -182,6 +190,8 @@ func (b Bytecode) String() string {
 		return "APPEND"
 	case InstructionAccessProperty:
 		return "ACCESS_PROPERTY"
+	case InstructionConcatLists:
+		return "CONCAT_LISTS"
 	}
 	return "UNDEFINED"
 }
@@ -202,7 +212,7 @@ func (c Chunk) String() string {
 	b.WriteString("=-= constants =-=\n")
 
 	for i, ct := range c.Constants {
-		b.WriteString(fmt.Sprintf("c=%d \t%s\n", i, ct))
+		b.WriteString(fmt.Sprintf("c=%d \t%s\n", i, ct.DebugString()))
 
 		f, ok := ct.(*FunctionValue)
 		if ok {
@@ -228,6 +238,16 @@ func RegisterGOBTypes() {
 		Params: nil,
 		Chunk:  nil,
 	})
+
+	// Signatures
+	gob.Register(&NilSignature{})
+	gob.Register(&NumberSignature{})
+	gob.Register(&StringSignature{})
+	gob.Register(&FunctionSignature{})
+	gob.Register(&ListSignature{})
+	gob.Register(&ObjectSignature{})
+	gob.Register(&BooleanSignature{})
+
 }
 
 func (c Chunk) Serialize() []byte {
@@ -287,38 +307,108 @@ type Call struct {
 var DefaultGlobals = map[string]Value{
 	"write": &BuiltinFunctionValue{
 		"write", // always remember where you come from...
-		[]string{"value"},
+		&FunctionSignature{
-		func(_ *VM, this Value, v map[string]Value) (Value, error) {
+			[]TypeSignature{&StringSignature{}},
-			println(v["value"].String())
+			&NilSignature{},
+		},
+		func(_ *VM, this Value, v []Value) (Value, error) {
+			println(v[0].String())
 			return nil, nil
 		},
 		nil,
+		false,
 	},
 	"print": &BuiltinFunctionValue{
 		"print",
-		[]string{"value"},
+		&FunctionSignature{
-		func(_ *VM, this Value, v map[string]Value) (Value, error) {
+			[]TypeSignature{&StringSignature{}},
-			print(v["value"].String())
+			&NilSignature{},
+		},
+		func(_ *VM, this Value, v []Value) (Value, error) {
+			print(v[0].String())
 			return nil, nil
 		},
 		nil,
+		false,
 	},
 	"format": &BuiltinFunctionValue{
 		"format",
-		[]string{"format_string", "values"},
+		&FunctionSignature{
-		func(vm *VM, value Value, m map[string]Value) (Value, error) {
+			[]TypeSignature{
-			valuies := m["values"].(*ListValue).items
+				&StringSignature{},
+				&ListSignature{
+					&AnySignature{},
+				},
+			},
+			&StringSignature{},
+		},
+		func(vm *VM, value Value, m []Value) (Value, error) {
+			b := strings.Builder{}
+			template := m[0].(*StringValue).Text
+			valuies := m[1].(*ListValue).Items
 
-			return GoToValue(fmt.Sprintf(m["format_string"].String(), valuies)), nil
+			vi := 0
+			last := 0
+			for i := 0; i < len(template); i++ {
+				if template[i] == '%' {
+					b.WriteString(template[last:i])
+					b.WriteString(valuies[vi].String())
+					vi++
+					last = i + 1
+				}
+			}
+
+			b.WriteString(template[last:])
+
+			return GoToValue(b.String()), nil
 		},
 		nil,
+		true,
+	},
+	"char": &BuiltinFunctionValue{
+		"char",
+		&FunctionSignature{
+			[]TypeSignature{&NumberSignature{}},
+			&StringSignature{},
+		},
+		func(vm *VM, this Value, args []Value) (Value, error) {
+			n := args[0].(*NumberValue).Number
+			b := byte(n)
+
+			return &StringValue{
+				string([]byte{b}),
+			}, nil
+		},
+		nil,
+		true,
+	},
+	"byte": &BuiltinFunctionValue{
+		"char",
+		&FunctionSignature{
+			[]TypeSignature{&StringSignature{}},
+			&NumberSignature{},
+		},
+		func(vm *VM, this Value, args []Value) (Value, error) {
+			s := args[0].(*StringValue).Text
+			b := []byte(s)[0]
+
+			return &NumberValue{float64(b)}, nil
+		},
+		nil,
+		true,
 	},
 	"assertEq": &BuiltinFunctionValue{
 		"assertEq",
-		[]string{"a", "b"},
+		&FunctionSignature{
-		func(vm *VM, this Value, params map[string]Value) (Value, error) {
+			[]TypeSignature{
-			a := params["a"]
+				&AnySignature{},
-			b := params["b"]
+				&AnySignature{},
+			},
+			&NilSignature{},
+		},
+		func(vm *VM, this Value, params []Value) (Value, error) {
+			a := params[0]
+			b := params[1]
 
 			if !a.Equals(b) {
 				return nil, errors.New(fmt.Sprintf("assertion failed: %s does not equal %s", a, b))
@@ -327,13 +417,20 @@ var DefaultGlobals = map[string]Value{
 			return &NilValue{}, nil
 		},
 		nil,
+		false,
 	},
 	"assertNotEq": &BuiltinFunctionValue{
 		"assertNotEq",
-		[]string{"a", "b"},
+		&FunctionSignature{
-		func(vm *VM, this Value, params map[string]Value) (Value, error) {
+			[]TypeSignature{
-			a := params["a"]
+				&AnySignature{},
-			b := params["b"]
+				&AnySignature{},
+			},
+			&NilSignature{},
+		},
+		func(vm *VM, this Value, params []Value) (Value, error) {
+			a := params[0]
+			b := params[1]
 
 			if a.Equals(b) {
 				return nil, errors.New(fmt.Sprintf("assertion failed: %s does not equal %s", a, b))
@@ -342,6 +439,85 @@ var DefaultGlobals = map[string]Value{
 			return &NilValue{}, nil
 		},
 		nil,
+		false,
+	},
+	"str": &BuiltinFunctionValue{
+		"str",
+		&FunctionSignature{
+			[]TypeSignature{&AnySignature{}},
+			&StringSignature{},
+		},
+		func(vm *VM, _ Value, args []Value) (Value, error) {
+			return GoToValue(args[0].String()), nil
+		},
+		nil,
+		true,
+	},
+	"type": &BuiltinFunctionValue{
+		Name: "type",
+		Signature: &FunctionSignature{
+			In:  []TypeSignature{&AnySignature{}},
+			Out: &StringSignature{},
+		},
+		F: func(vm *VM, this Value, args []Value) (Value, error) {
+			v := args[0]
+			sig := SignatureOf(v)
+
+			return GoToValue(sig.String()), nil
+		},
+		Constant: true,
+	},
+	"exit": &BuiltinFunctionValue{
+		"exit",
+		&FunctionSignature{
+			[]TypeSignature{&NumberSignature{}},
+			&NilSignature{},
+		},
+		func(vm *VM, this Value, args []Value) (Value, error) {
+			os.Exit(int(args[0].(*NumberValue).Number))
+			return &NilValue{}, nil
+		},
+		nil,
+		false,
+	},
+	"floor": &BuiltinFunctionValue{
+		"floor",
+		&FunctionSignature{
+			[]TypeSignature{&NumberSignature{}},
+			&NumberSignature{},
+		},
+		func(vm *VM, this Value, args []Value) (Value, error) {
+			return &NumberValue{math.Floor(args[0].(*NumberValue).Number)}, nil
+		},
+		nil,
+		true,
+	},
+	"ceil": &BuiltinFunctionValue{
+		"ceil",
+		&FunctionSignature{
+			[]TypeSignature{&NumberSignature{}},
+			&NumberSignature{},
+		},
+		func(vm *VM, this Value, args []Value) (Value, error) {
+			return &NumberValue{math.Ceil(args[0].(*NumberValue).Number)}, nil
+		},
+		nil,
+		true,
+	},
+	"roundd": &BuiltinFunctionValue{
+		"roundd",
+		&FunctionSignature{
+			[]TypeSignature{&NumberSignature{}, &NumberSignature{}},
+			&NumberSignature{},
+		},
+		func(vm *VM, this Value, args []Value) (Value, error) {
+			x := args[0].(*NumberValue).Number
+			decimals := args[1].(*NumberValue).Number
+			multiplier := math.Pow(10, decimals)
+			return &NumberValue{math.Round(x*multiplier) / multiplier}, nil
+		},
+		nil,
+		true,
 	},
 }
 
@@ -393,29 +569,34 @@ func (vm *VM) Next() bool {
 		vm.stack.Push(vm.ReadConstant())
 
 	case InstructionAdd:
-		r := vm.stack.Pop().(*NumberValue).float64
+		r := vm.stack.Pop().(*NumberValue).Number
-		l := vm.stack.Pop().(*NumberValue).float64
+		l := vm.stack.Pop().(*NumberValue).Number
 
 		vm.stack.Push(&NumberValue{l + r})
 
 	case InstructionSub:
-		r := vm.stack.Pop().(*NumberValue).float64
+		r := vm.stack.Pop().(*NumberValue).Number
-		l := vm.stack.Pop().(*NumberValue).float64
+		l := vm.stack.Pop().(*NumberValue).Number
 
 		vm.stack.Push(&NumberValue{l - r})
 
 	case InstructionMul:
-		r := vm.stack.Pop().(*NumberValue).float64
+		r := vm.stack.Pop().(*NumberValue).Number
-		l := vm.stack.Pop().(*NumberValue).float64
+		l := vm.stack.Pop().(*NumberValue).Number
 
 		vm.stack.Push(&NumberValue{l * r})
 
 	case InstructionDiv:
-		r := vm.stack.Pop().(*NumberValue).float64
+		r := vm.stack.Pop().(*NumberValue).Number
-		l := vm.stack.Pop().(*NumberValue).float64
+		l := vm.stack.Pop().(*NumberValue).Number
 
 		vm.stack.Push(&NumberValue{l / r})
 
+	case InstructionNegate:
+		v := vm.stack.Pop().(*NumberValue).Number
+
+		vm.stack.Push(&NumberValue{-v})
+
 	case InstructionEquals:
 		vm.stack.Push(
 			&BoolValue{vm.stack.Pop().Equals(vm.stack.Pop())},
@@ -427,40 +608,40 @@ func (vm *VM) Next() bool {
 		)
 
 	case InstructionNot:
-		b := vm.stack.Pop().(*BoolValue).bool
+		b := vm.stack.Pop().(*BoolValue).Boolean
 		vm.stack.Push(&BoolValue{!b})
 
 	case InstructionAnd:
-		r := vm.stack.Pop().(*BoolValue).bool
+		r := vm.stack.Pop().(*BoolValue).Boolean
-		l := vm.stack.Pop().(*BoolValue).bool
+		l := vm.stack.Pop().(*BoolValue).Boolean
 		vm.stack.Push(&BoolValue{l && r})
 
 	case InstructionOr:
-		r := vm.stack.Pop().(*BoolValue).bool
+		r := vm.stack.Pop().(*BoolValue).Boolean
-		l := vm.stack.Pop().(*BoolValue).bool
+		l := vm.stack.Pop().(*BoolValue).Boolean
 		vm.stack.Push(&BoolValue{l || r})
 
 	case InstructionLess:
-		r := vm.stack.Pop().(*NumberValue).float64
+		r := vm.stack.Pop().(*NumberValue).Number
-		l := vm.stack.Pop().(*NumberValue).float64
+		l := vm.stack.Pop().(*NumberValue).Number
 
 		vm.stack.Push(&BoolValue{l < r})
 
 	case InstructionLessOrEqual:
-		r := vm.stack.Pop().(*NumberValue).float64
+		r := vm.stack.Pop().(*NumberValue).Number
-		l := vm.stack.Pop().(*NumberValue).float64
+		l := vm.stack.Pop().(*NumberValue).Number
 
 		vm.stack.Push(&BoolValue{l <= r})
 
 	case InstructionGreater:
-		r := vm.stack.Pop().(*NumberValue).float64
+		r := vm.stack.Pop().(*NumberValue).Number
-		l := vm.stack.Pop().(*NumberValue).float64
+		l := vm.stack.Pop().(*NumberValue).Number
 
 		vm.stack.Push(&BoolValue{l > r})
 
 	case InstructionGreaterOrEqual:
-		r := vm.stack.Pop().(*NumberValue).float64
+		r := vm.stack.Pop().(*NumberValue).Number
-		l := vm.stack.Pop().(*NumberValue).float64
+		l := vm.stack.Pop().(*NumberValue).Number
 
 		vm.stack.Push(&BoolValue{l >= r})
 
@@ -479,7 +660,7 @@ func (vm *VM) Next() bool {
 			for i := len(f.Params) - 1; i >= 0; i-- {
 				p := vm.stack.Current - Pos(len(f.Params)) + Pos(i)
 				vm.stack.items[p] = &VariableValue{
-					f.Params[i],
+					f.Params[i].Name,
 					vm.stack.items[p],
 					vm.scope,
 				}
@@ -494,10 +675,10 @@ func (vm *VM) Next() bool {
 			vm.chunk = f.Chunk
 			vm.ip = 0
 		case *BuiltinFunctionValue:
-			args := map[string]Value{}
+			args := make([]Value, len(f.Signature.In))
 
-			for i := len(f.Parameters) - 1; i >= 0; i-- {
+			for i := len(f.Signature.In) - 1; i >= 0; i-- {
-				args[f.Parameters[i]] = vm.stack.Pop()
+				args[i] = vm.stack.Pop()
 			}
 
 			v, err := f.F(vm, f.Parent, args)
@@ -519,12 +700,12 @@ func (vm *VM) Next() bool {
 
 	case InstructionJumpFalse:
 		n := vm.NextU16()
-		if !vm.stack.Pop().(*BoolValue).bool {
+		if !vm.stack.Pop().(*BoolValue).Boolean {
 			vm.ip += Pos(n)
 		}
 
 	case InstructionGetLocal:
-		name := vm.GetConstant(vm.NextByte()).(*StringValue).string
+		name := vm.GetConstant(vm.NextByte()).(*StringValue).Text
 		v := vm.getVar(name)
 
 		if v == nil {
@@ -536,7 +717,7 @@ func (vm *VM) Next() bool {
 
 	case InstructionSetLocal:
 		value := vm.stack.Pop().(Value)
-		name := vm.GetConstant(vm.NextByte()).(*StringValue).string
+		name := vm.GetConstant(vm.NextByte()).(*StringValue).Text
 
 		v := vm.getVar(name)
 
@@ -544,19 +725,19 @@ func (vm *VM) Next() bool {
 			vm.error(fmt.Sprintf("cannot set local: undefined variable %s", name))
 		}
 
-		v.value = value
+		v.value = value.Clone()
 
 	case InstructionDeclareLocal:
 		vm.addVar(
-			vm.GetConstant(vm.NextByte()).(*StringValue).string,
+			vm.GetConstant(vm.NextByte()).(*StringValue).Text,
-			vm.stack.Pop().(Value),
+			vm.stack.Pop().Clone(),
 		)
 
 	case InstructionGetGlobal:
-		vm.stack.Push(vm.globals[vm.GetConstant(vm.NextByte()).(*StringValue).string])
+		vm.stack.Push(vm.globals[vm.GetConstant(vm.NextByte()).(*StringValue).Text])
 
 	case InstructionSetGlobal:
-		vm.globals[vm.GetConstant(vm.NextByte()).(*StringValue).string] = vm.stack.Pop()
+		vm.globals[vm.GetConstant(vm.NextByte()).(*StringValue).Text] = vm.stack.Pop()
 
 	case InstructionTrue:
 		vm.stack.Push(&BoolValue{true})
@@ -570,20 +751,32 @@ func (vm *VM) Next() bool {
 	case InstructionFormList:
 		n := int(vm.NextU16())
 
-		items := make([]Value, n+1)
+		items := make([]Value, n)
-		for i := 0; i <= n; i++ {
+		for i := n - 1; i >= 0; i-- {
-			items[n-i] = vm.stack.Pop()
+			items[i] = vm.stack.Pop()
 		}
 
+		vm.stack.Push(&ListValue{
+			items,
+		})
+
 	case InstructionNewList:
 		vm.stack.Push(&ListValue{[]Value{}})
 
 	case InstructionAppend:
 		value := vm.stack.Pop()
 		list := vm.stack.Pop().(*ListValue)
-		list.items = append(list.items, value)
+		list.Items = append(list.Items, value)
 		vm.stack.Push(list)
 
+	case InstructionConcatLists:
+		r := vm.stack.Pop().(*ListValue)
+		l := vm.stack.Pop().(*ListValue)
+
+		vm.stack.Push(&ListValue{
+			append(l.Items, r.Items...),
+		})
+
 	case InstructionDescend:
 		vm.descend()
 
@@ -595,8 +788,8 @@ func (vm *VM) Next() bool {
 		vm.stack.Push(&StringValue{v.String()})
 
 	case InstructionStringConcatenation:
-		r := vm.stack.Pop().(*StringValue).string
+		r := vm.stack.Pop().(*StringValue).Text
-		l := vm.stack.Pop().(*StringValue).string
+		l := vm.stack.Pop().(*StringValue).Text
 
 		vm.stack.Push(&StringValue{l + r})
 
@@ -645,7 +838,7 @@ func (vm *VM) Call(v Value, args []Value) (Value, error) {
 		})
 
 		for i := 0; i < len(f.Params); i++ {
-			vm.addVar(f.Params[i], args[i])
+			vm.addVar(f.Params[i].Name, args[i])
 		}
 
 		if f.Parent != nil {
@@ -660,25 +853,21 @@ func (vm *VM) Call(v Value, args []Value) (Value, error) {
 		for vm.chunk.Bytecode[vm.ip] != InstructionReturn && vm.Next() {
 		}
 
-		if vm.HasNext() {
 		vm.Next()
-		}
 
 		return vm.stack.Pop(), nil
 
 	case *BuiltinFunctionValue:
-		argies := map[string]Value{}
+		return f.F(vm, f.Parent, args)
-
-		for i, arg := range args {
-			argies[f.Parameters[i]] = arg
-		}
-
-		return f.F(vm, f.Parent, argies)
 	}
 
 	return nil, errors.New(fmt.Sprintf("value is not a function (%s)", v.DebugString()))
 }
 
+func (vm *VM) SetChunk(c *Chunk) {
+	vm.chunk = c
+}
+
 func (vm *VM) TryNextByte() (Bytecode, error) {
 	if !vm.HasNext() {
 		return 0, errors.New("there are no more instructions")

core/vm_test.go

@@ -76,13 +76,13 @@ func TestNewVM(t *testing.T) {
 	}
 
 	// should have given stack size
-	if vm.stack.Size != stackSize {
+	if vm.stack.Capacity != stackSize {
-		t.Errorf("vm.stack.Size = %d, want %d", vm.stack.Size, stackSize)
+		t.Errorf("vm.stack.Capacity = %d, want %d", vm.stack.Capacity, stackSize)
 	}
 
 	// should have given call stack size
-	if vm.call.Size != callstackSize {
+	if vm.call.Capacity != callstackSize {
-		t.Errorf("vm.call.Size = %d, want %d", vm.call.Size, callstackSize)
+		t.Errorf("vm.call.Capacity = %d, want %d", vm.call.Capacity, callstackSize)
 	}
 }
 
@@ -442,7 +442,16 @@ func GetExecutionTestData() map[string]struct {
 					&NumberValue{2},
 					&FunctionValue{
 						Name: "sum",
-						Params: []string{"a", "b"},
+						Params: []FunctionParameter{
+							{
+								"a",
+								&NumberSignature{},
+							},
+							{
+								"b",
+								&NumberSignature{},
+							},
+						},
 						Chunk: NewChunk(
 							[]Bytecode{
 								InstructionGetLocal, 0,
@@ -476,7 +485,16 @@ func GetExecutionTestData() map[string]struct {
 					&NumberValue{2},
 					&FunctionValue{
 						Name: "sum",
-						Params: []string{"a", "b"},
+						Params: []FunctionParameter{
+							{
+								"a",
+								&NumberSignature{},
+							},
+							{
+								"b",
+								&NumberSignature{},
+							},
+						},
 						Chunk: NewChunk(
 							[]Bytecode{
 								InstructionGetLocal, 0,
@@ -493,7 +511,12 @@ func GetExecutionTestData() map[string]struct {
 					},
 					&FunctionValue{
 						Name: "square",
-						Params: []string{"n"},
+						Params: []FunctionParameter{
+							{
+								"n",
+								&NumberSignature{},
+							},
+						},
 						Chunk: NewChunk(
 							[]Bytecode{
 								InstructionGetLocal, 0,
@@ -514,7 +537,12 @@ func GetExecutionTestData() map[string]struct {
 					"square",
 					&FunctionValue{
 						Name: "square",
-						Params: []string{"n"},
+						Params: []FunctionParameter{
+							{
+								"n",
+								&NumberSignature{},
+							},
+						},
 						Chunk: NewChunk(
 							[]Bytecode{
 								InstructionGetLocal, 0,
@@ -532,6 +560,37 @@ func GetExecutionTestData() map[string]struct {
 				&NumberValue{5},
 			},
 		},
+		"list_concat": {
+			NewChunk(
+				[]Bytecode{
+					InstructionConstant, 0,
+					InstructionConstant, 1,
+					InstructionConcatLists,
+				},
+				[]Value{
+					&ListValue{
+						[]Value{
+							&NumberValue{1},
+							&NumberValue{2},
+						},
+					},
+					&ListValue{
+						[]Value{
+							&NumberValue{3},
+						},
+					},
+				},
+			),
+			[]Value{
+				&ListValue{
+					[]Value{
+						&NumberValue{1},
+						&NumberValue{2},
+						&NumberValue{3},
+					},
+				},
+			},
+		},
 	}
 }
 

emoji.ang

@@ -0,0 +1,2 @@
+
+write(char(0x12) + char(0x85) + char(0x07))

examples/pi-approx.ang

@@ -18,7 +18,7 @@ while n <= terms {
 tot = tot * 6
 
 # get the absolute value of a number
-func abs(x) {
+func abs(x: number) number {
 	if x < 0 {
 		return -x
 	}
@@ -30,7 +30,7 @@ func abs(x) {
 # see: https://en.wikipedia.org/wiki/Newton's_method
 # The required accuracy
 SQRT_ACC := 0.00000001
-func sqrt(x) {
+func sqrt(x: number) number {
     pg := 0 # previous guess
     g := 1 # current guess
 
@@ -45,4 +45,4 @@ func sqrt(x) {
 tot = sqrt(tot)
 
 # output the result
-write(tot)
+write(str(tot))

examples/pi-approx.py

@@ -0,0 +1,36 @@
+terms = 100000
+
+tot = 0
+
+n = 1
+while n <= terms:
+    tot = tot + 1 / (n*n)
+    n = n + 1
+
+tot = tot * 6
+
+# get the absolute value of a number
+def abs(x):
+	if x < 0:
+		return -x
+	return x
+
+# calculate an approximation of the square root of tot using
+# newton's method.
+# see: https://en.wikipedia.org/wiki/Newton's_method
+# The required accuracy
+SQRT_ACC = 0.00000001
+def sqrt(x):
+    pg = 0 # previous guess
+    g = 1 # current guess
+
+    while abs(pg - g) >= SQRT_ACC:
+        pg = g
+        g = (pg + tot/pg)/2
+
+    return g
+
+tot = sqrt(tot)
+
+# output the result
+print(tot)

examples/pøck.ang

@@ -0,0 +1,16 @@
+import "math.ang"
+
+func r_x(t) {
+    return 8*(exp(-t) - t)
+}
+
+func r_y(t) {
+    return 5*(exp(-t) - t)
+}
+
+func r(t) {
+    return format("(%s, %s)", [r_x(t), r_y(t)])
+}
+
+write(r(1))
+write()

examples/recursive.ang

@@ -1,15 +1,14 @@
-
+# This program computes the fibonacci numbers using recursion (O(2^n))
-# fibonacci sequence
+# It is very slow
-func fib(n) {
+func fib(x: number) number {
-    if n <= 1 {
+	if x <= 1 {
-        return n
+		return x
 	}
-
+	return fib(x - 1) + fib(x - 2)
-    return fib(n - 1) + fib(n - 2)
 }
 
 n := 0
-while n < 10 {
+while n < 100 {
-    write(fib(n))
+	write(str(fib(n)))
 	n = n + 1
 }

examples/solving.ang

@@ -0,0 +1,13 @@
+import "../lib/math.ang"
+
+a := 120
+b := 10
+
+# find log_b(a)
+func f(x: number)number {
+    return pow(b, x) - a
+}
+
+log_b := newtons(f)
+write(str(log_b))
+write("inverse: "+str(pow(b, log_b))+" = "+str(a))

fails.ang

@@ -0,0 +1,4 @@
+import "lib/honning.ang"
+
+write(_bell+_italic+"Hello "+_underline+"world "+_strike+"micheal"+_reset)
+

imp.ang

@@ -0,0 +1,15 @@
+
+func is_cool(x: number|string) boolean {
+    if x == "cool" {
+        return true
+    } else if x == 69 {
+        return true
+    }
+
+    return nil
+}
+
+write(str(is_cool("not cool")))
+write(str(is_cool("cool")))
+write(str(is_cool(0)))
+write(str(is_cool(69)))

lib/honning.ang

@@ -0,0 +1,15 @@
+
+_bell := char(0x07)
+
+ESC := char(0x1B)
+CSI := ESC + "["
+
+_reset := CSI + "0m"
+_bold := CSI + "1m"
+_faint := CSI + "2m"
+_italic := CSI + "3m"
+_underline := CSI + "4m"
+_slow_blink := CSI + "5m"
+_rapid_blink := CSI + "6m"
+_strike := CSI + "9m"
+_primary_font := CSI + "10m"

lib/list.ang

@@ -0,0 +1,12 @@
+
+func map(list: list[any], f: func(any)any) list[any] {
+    out := []
+
+    i := 0
+    while i < list.length() {
+        out.append(f(list.at(i)))
+        i = i + 1
+    }
+
+    return out
+}

lib/math.ang

@@ -7,7 +7,7 @@ E := 2.718281828459045235360287471352
 #   Get the absolute value of a number. If x is negative, the returned
 #   value is positive and equal to `-x`. If x is positive or zero, the
 #   returned value is x.
-func abs(x) {
+func abs(x: number) number {
     # if the number is negative
     if x < 0 {
         # negate it so it's positive
@@ -17,13 +17,31 @@ func abs(x) {
     return x
 }
 
+DERIVE_DX := 0.00000001
+func derive(f: func(number)number, x: number) number {
+    return (f(x + DERIVE_DX) - f(x))/DERIVE_DX
+}
+
+NEWTONS_ACC := 0.000000000001
+func newtons(f: func(number)number) number {
+    pg := 0
+    g := 1
+
+    while abs(g - pg) > NEWTONS_ACC {
+        pg = g
+        g = pg - f(pg) / derive(f, pg)
+    }
+
+    return g
+}
+
 MAX_SQRT_DX := 0.0000001
 
 # sqrt(x)
 # x: number
 #   Calculate the approximate square root using newton's method until
 #   the accuracy has increased by less than the variable `MAX_SQRT_DX`.
-func sqrt(x) {
+func sqrt(x: number) number {
     ng := x
     g := 1
 
@@ -42,23 +60,19 @@ func sqrt(x) {
 #   Return the whole number part of the number. if x is a whole number,
 #   the returned value is x. If x is not a whole number, the closest
 #   whole number which is less than or equal to x is returned.
-func floor(x) {
+
-    # todo
-}
 
 # ceil(x)
 # x: number
 #   Return the whole number part of the number. if x is a whole number,
 #   the returned value is x. If x is not a whole number, the closest
 #   whole number which is greater than or equal to x is returned.
-func ceil(x) {
+
-    # todo
-}
 
 # round(x)
 # x: number
 #   Return the closest whole number to the value x.
-func round(x) {
+func round(x: number) number {
     f := floor(x)
 
     if x - f > 0.5 {
@@ -68,15 +82,128 @@ func round(x) {
     return f
 }
 
+# mod(x, n)
+# x: number; any number
+# n: number; the number to divide by
+#   Return the rest from a division of x by n.
+func mod(x: number, n: number) number {
+    if x == 0 {
+        return 0
+    }
+
+    if x < 0 {
+        while x + n <= 0 {
+            x = x + n
+        }
+    } else {
+        while x - n >= 0 {
+            x = x - n
+        }
+    }
+
+    return x
+}
+
+# sm_exp(x)
+# x: number; any number between 0 and 1
+#   Get an approximate value of e raised to the power of x.
+#   This value is only reasonable if 0<x<1.
+#   It is approximated using the taylor series of e**x.
+SM_EXP_ACC := 0.00000000001
+func sm_exp(x: number) number {
+    p_tot := 0
+    tot := 1
+    n := 1
+    x_pow := x
+    f := 1
+    while abs(tot - p_tot) > SM_EXP_ACC {
+        p_tot = tot
+        t := x_pow / f
+        tot = tot + t
+        f = f * (n+1)
+        x_pow = x_pow * x
+        n = n + 1
+    }
+
+    return tot
+}
+
+# exp(x)
+# x: number; any number
+#   Get an approximate value of e raised to the power of x.
+func exp(x: number) number {
+    n := abs(x)
+    tot := 1
+    while n >= 1 {
+        tot = tot * E
+        n = n - 1
+    }
+
+    if n > 0 {
+        tot = tot * sm_exp(n)
+    }
+
+    if x < 0 {
+        return 1/tot
+    } else {
+        return tot
+    }
+}
+
+# ln(x)
+# x: number; any number
+#   Get the approximate value of the natural logarithm
+#   This function uses newton's method to approximate.
+LN_ACC := 0.0000000001
+func ln(x: number) number {
+    pg := 0
+    g := 1
+
+    while abs(pg - g) > LN_ACC {
+        pg = g
+        g = pg + x / exp(pg) - 1
+    }
+
+    return g
+}
+
+# pow(x, p)
+# x: number; any number. The base
+# p: number; the value of the exponent
+#   Raise any number to any power (x^p)
+func pow(x: number, p: number) number {
+    return exp(p*ln(x))
+}
+
+# log(x, b)
+# x: number; any number greater than 0
+# b: number; any number as the base
+#   Calculate the approximate value of the logarithm
+#   of a with b as base.
+LOG_ACC := 0.0000001
+func log(a: number, b: number) number {
+    ln_b := ln(b)
+
+    pg := 0
+    g := 1
+
+    while abs(g - pg) > LOG_ACC {
+        pg = g
+        g = pg - 1/ln_b - a/(ln_b*pow(b, pg))
+    }
+
+    return g
+}
+
 # sin(x)
 # x: number; an angle in radians
 #   Get the sine of an angle (in radians). https://en.wikipedia.org/wiki/Sine_and_cosine
 #   TODO: use hashmap with precomputed values and linear interpolation
-func sin(x) {
+func sin(x: number) number {
     f := 1
     x = mod(x, 2*PI)
     if x > PI {
-        x = -x
+        x = PI - x
         f = -1
     }
 
@@ -101,106 +228,13 @@ func sin(x) {
 # cos(x)
 # x: number; an angle in radians
 #   Get the cosine of an angle (in radians). https://en.wikipedia.org/wiki/Sine_and_cosine
-func cos(x) {
+func cos(x: number) number {
     # todo
 }
 
 # tan(x)
 # x: number; an angle in radians
 #   Get the tangent of an angle. https://en.wikipedia.org/wiki/Tangent
-func tan(x) {
+func tan(x: number) number {
     # todo
 }
-
-# mod(x, n)
-# x: number; any number
-# n: number; the number to divide by
-#   Return the rest from a division of x by n.
-func mod(x, n) {
-    if x == 0 {
-        return 0
-    }
-
-    if x < 0 {
-        while x + n <= 0 {
-            x = x + n
-        }
-    } else {
-        while x - n >= 0 {
-            x = x - n
-        }
-    }
-
-    return x
-}
-
-# ln(x)
-# x: number; any number
-#   Get the approximate value of the natural logarithm
-#   This function uses newton's method to approximate.
-LN_ACC := 0.000000001
-func ln(x) {
-    pg := 0
-    g := 1
-
-    while abs(pg - g) > LN_ACC {
-        pg = g
-        g = pg + x / exp(pg) - 1
-    }
-
-    return g
-}
-
-# sm_exp(x)
-# x: number; any number between 0 and 1
-#   Get an approximate value of e raised to the power of x.
-#   This value is only reasonable if 0<x<1.
-#   It is approximated using the taylor series of e**x.
-SM_EXP_ACC := 0.00000000001
-func sm_exp(x) {
-    p_tot := 0
-    tot := 1
-    n := 1
-    x_pow := x
-    f := 1
-    while abs(tot - p_tot) > SM_EXP_ACC {
-        p_tot = tot
-        t := x_pow / f
-        tot = tot + t
-        f = f * (n+1)
-        x_pow = x_pow * x
-        n = n + 1
-    }
-
-    return tot
-}
-
-# exp(x)
-# x: number; any number
-#   Get an approximate value of e raised to the power of x.
-func exp(x) {
-    n := abs(x)
-    tot := 1
-    while n >= 1 {
-        tot = tot * E
-        n = n - 1
-    }
-
-    if n > 0 {
-        tot = tot * sm_exp(n)
-    }
-
-    if x < 0 {
-        return 1/tot
-    } else {
-        return tot
-    }
-}
-
-# pow(x, p)
-# x: number; any number. The base
-# p: number; the value of the exponent
-#   Raise any number to any power (x^p)
-func pow(x, p) {
-    return exp(p*ln(x))
-}

lib/testing.ang

@@ -0,0 +1,25 @@
+
+NAMESPACE := ""
+
+func namespace(name: string, test: func()) {
+    NAMESPACE = name
+    test()
+}
+
+func assertEqual(a: any, b: any) {
+    if a != b {
+        write(format("assertion error: % should (but doesn't) equal %", [a, b]))
+        exit(1)
+    } else if env("DEBUG") != "" {
+        write(format("assertion success: % equals %", [a, b]))
+    }
+}
+
+func assertNotEqual(a: any, b: any) {
+    if a == b {
+        write(format("assertion error: % shouldn't (but does) equal %", [a, b]))
+        exit(1)
+    } else if env("DEBUG") != "" {
+        write(format("assertion success: % doesn't equal %", [a, b]))
+    }
+}

lib/util.ang

@@ -0,0 +1,4 @@
+
+func memoize(f) {
+
+}

test_all.sh

@@ -1,22 +1,46 @@
-#!/bin/zsh
+#!/bin/bash
 
-echo '== Building CLI =='
+echo '=== Building CLI ==='
-cd cli
+cd cli || exit 1
-go build .
+if ! go build .; then
+  echo "=== Had error building CLI ==="
+  exit 1
+else
+  echo "=+= Successfully built CLI =+="
+fi
 cd ..
 
+echo "=== Running go core tests ==="
+cd core || exit 1
+if ! go test .; then
+  echo "=x= Core testing failed =x= "
+  exit 1
+else
+  echo "=+= Successfully ran core tests =+="
+fi
+cd ..
 
-echo '== Testing anglais =='
+errors=()
 
-for file in ./tests/*.ang; do
+echo '=== Testing anglais ==='
-  echo "-- Test-running file $file --"
+
+# read files
+for file in $(find tests -type f); do
+  echo "-v- Test-running file $file -v-"
 
   if ! ./cli/cli run "$file"; then
-    echo "-- Error --"
+    echo "-x- Error -x-"
-    exit 1
+    errors+=("$file")
   else
-    echo "-- Success --"
+    echo "-+- Success -+-"
   fi
 done
 
-echo '== Successfully ran all tests =='
+
+if [ 0 -ne "$(wc -w <<< "${errors[@]}")" ]; then
+  echo "=x= Errors occured while executing =x="
+  echo "erroring files: $(printf '%s ' "${errors[@]}")"
+  exit 1
+else
+  echo '=+= Successfully ran all tests =+='
+fi

tests/conditions.ang

@@ -3,9 +3,8 @@ assertEq(1, 1)
 assertEq(0, 0)
 assertEq("", "")
 
-assertEq([], [])
+assertEq([]number, []number)
 assertEq([3, 1, 4, 1], [3, 1, 4, 1])
-assertEq([true, 1024, nil, "Hello world!"], [true, 1024, nil, "Hello world!"])
 
 # Inequality
 assertNotEq(2, 3)

tests/hex.ang

@@ -0,0 +1,3 @@
+
+assertEq(0x00, 0)
+assertEq(0xFF, 255)

tests/list.ang

@@ -1,20 +1,20 @@
-list := []
+list := []number
 
 x := 1
 while x <= 1000 {
     list.append(x)
-    assertEq(list.reduce(func(tot, a){
+    assertEq(list.reduce(func(tot: number, a: number) number {
         return tot + a
     }, 0), x*(x + 1)/2)
 
     x = x + 1
 }
 
-func sum(a, b) {
+func sum(a: number, b: number) number {
     return a + b
 }
 
-list = []
+list = []number
 x = 1
 while x <= 100 {
     list.append(2*x - 1)
@@ -22,3 +22,6 @@ while x <= 100 {
 
     x = x + 1
 }
+
+assertEq([1, 2] + [3], [1, 2, 3])
+assertEq(["Eny", "meanie"] + ["minie", "moe"], ["Eny", "meanie", "minie", "moe"])

tests/recursive_fib.ang

@@ -2,11 +2,10 @@
 fibonacci_numbers := [
     0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377,
     610, 987, 1597, 2584, 4181, 6765, 10946, 17711, 28657,
-    46368, 75025, 121393, 196418, 317811, 514229, 832040,
+    46368, 75025, 121393, 196418, 317811, 514229, 832040
-    1346269, 2178309, 3524578, 5702887, 9227465, 14930352
 ]
 
-func fib(n) {
+func fib(n: number) number {
     if n < 2 {
         return n
     }
@@ -16,11 +15,12 @@ func fib(n) {
 
 n := 0
 while n < fibonacci_numbers.length() {
-    print("_")
+    print("-")
     n = n + 1
 }
 
-write("")
+# return to start of line (with carriage return \r)
+print(char(0x0D))
 
 x := 0
 while x < fibonacci_numbers.length() {

tests/refs.ang

@@ -0,0 +1,13 @@
+
+list := []number
+
+list.append(1)
+list.append(2)
+
+assertEq(list, [1, 2])
+
+other := list
+other.append(3)
+
+assertEq(other, [1, 2, 3])
+assertEq(list, [1, 2])

tests/scope.ang

@@ -4,9 +4,12 @@ a := 2
 {
     a := 3
     assertEq(a, 3)
+    breakpoint
 
     a = 4
     assertEq(a, 4)
+    breakpoint
 }
 
 assertEq(a, 2)
+breakpoint

tests/simple_func.ang

@@ -1,5 +1,5 @@
 
-func sum(a, b) {
+func sum(a: number, b: number) number {
     return a + b
 }
 

tests/types.ang

@@ -0,0 +1,8 @@
+
+assertEq(type(1), "number")
+assertEq(type("Hello"), "string")
+assertEq(type(true), "boolean")
+
+# lists
+assertEq(type(["Hello", "world"]), "list[string]")
+assertEq(type([0, 1]), "list[number]")

wasm/wasm.go

@@ -13,32 +13,22 @@ type JsResolver struct {
 	jsResolver js.Value
 }
 
-func (r *JsResolver) Resolve(name string) (core.Node, error) {
+func (r *JsResolver) IsSame(a, b string) bool {
+	return a == b
+}
+
+func (r *JsResolver) Resolve(name string) (string, error) {
 	jsv := r.jsResolver.Invoke(name)
 
 	if jsv.Type() == js.TypeUndefined {
-		return nil, errors.New("cannot find import with name " + name)
+		return "", errors.New("cannot find import with name " + name)
 	}
 
 	if jsv.Type() != js.TypeString {
-		return nil, errors.New("invalid value for source: " + jsv.String())
+		return "", errors.New("invalid value for source: " + jsv.String())
 	}
 
-	source := jsv.String()
+	return jsv.String(), nil
-
-	l := core.NewLexer(source)
-	tokens, err := l.Tokenize()
-	if err != nil {
-		return nil, err
-	}
-
-	p := core.NewParser(tokens)
-	tree, err := p.Parse()
-	if err != nil {
-		return nil, err
-	}
-
-	return tree, nil
 }
 
 func jsError(err error) interface{} {
@@ -55,7 +45,8 @@ func jsErrorOfString(err string) interface{} {
 func run(_ js.Value, args []js.Value) interface{} {
 	source := args[0].String()
 	outputHandler := args[1]
-	resolver := args[2]
+	errorHandler := args[2]
+	resolver := args[3]
 	log.Printf("got source: %s", source)
 
 	lexer := core.NewLexer(source)
@@ -67,17 +58,25 @@ func run(_ js.Value, args []js.Value) interface{} {
 
 	log.Printf("got tokens: %v", tokens)
 
-	parser := core.NewParser(tokens)
+	parser := core.NewParser(source, tokens)
 
-	tree, err := parser.Parse()
+	tree, err := parser.Parse(source)
 
 	if err != nil {
-		return jsErrorOfString(err.Error())
+		var e core.FormatedError
+		if errors.As(err, &e) {
+			errorHandler.Invoke(e.Format())
+			return nil
+		}
+		errorHandler.Invoke(err.Error())
+		return nil
 	}
 
 	log.Printf("Parsed tree: %s", tree.String())
 
-	compiler := core.NewCompiler()
+	compiler := core.NewCompiler([]rune(source))
+
+	log.Println("Set imports resolver")
 
 	compiler.SetImportsResolver(&JsResolver{
 		resolver,
@@ -91,6 +90,13 @@ func run(_ js.Value, args []js.Value) interface{} {
 
 	err = compiler.Compile(tree)
 	if err != nil {
+		var e core.CompilerError
+		if errors.As(err, &e) {
+			errorHandler.Invoke(e.Format())
+			return nil
+		}
+
+		errorHandler.Invoke(err.Error())
 		return nil
 	}
 
@@ -101,19 +107,27 @@ func run(_ js.Value, args []js.Value) interface{} {
 	// overwrite output
 	vm.SetGlobal("write", &core.BuiltinFunctionValue{
 		Name: "write",
-		Parameters: []string{"value"},
+		Signature: &core.FunctionSignature{
-		F: func(vm *core.VM, this core.Value, v map[string]core.Value) (core.Value, error) {
+			In:  []core.TypeSignature{&core.StringSignature{}},
-			log.Printf("Writing value: %s", v["value"].String())
+			Out: &core.NilSignature{},
-			outputHandler.Invoke(js.ValueOf(v["value"].String() + "\n"))
+		},
+		F: func(vm *core.VM, this core.Value, args []core.Value) (core.Value, error) {
+			s := args[0].String()
+			log.Printf("Writing value: %s", s)
+			outputHandler.Invoke(js.ValueOf(s + "\n"))
 			return nil, nil
 		},
 	})
 	vm.SetGlobal("print", &core.BuiltinFunctionValue{
 		Name: "print",
-		Parameters: []string{"value"},
+		Signature: &core.FunctionSignature{
-		F: func(vm *core.VM, this core.Value, v map[string]core.Value) (core.Value, error) {
+			In:  []core.TypeSignature{&core.StringSignature{}},
-			log.Printf("Printing value: %s", v["value"].String())
+			Out: &core.NilSignature{},
-			outputHandler.Invoke(js.ValueOf(v["value"].String()))
+		},
+		F: func(vm *core.VM, this core.Value, args []core.Value) (core.Value, error) {
+			s := args[0].String()
+			log.Printf("Printing value: %s", s)
+			outputHandler.Invoke(js.ValueOf(s))
 			return nil, nil
 		},
 	})