add general assert builtin

core/vm.go

@@ -470,6 +470,26 @@ var DefaultGlobals = map[string]Value{
 		nil,
 		true,
 	},
+	"assert": &BuiltinFunctionValue{
+		"assert",
+		&FunctionSignature{
+			[]TypeSignature{
+				&BooleanSignature{},
+			},
+			&NilSignature{},
+		},
+		func(vm *VM, this Value, params []Value) (Value, error) {
+			b := params[0].(*BoolValue)
+
+			if !b.Boolean {
+				return nil, errors.New(fmt.Sprintf("assertion failed: %s", b))
+			}
+
+			return &NilValue{}, nil
+		},
+		nil,
+		false,
+	},
 	"assertEq": &BuiltinFunctionValue{
 		"assertEq",
 		&FunctionSignature{

tests/conditions.ang

@@ -8,3 +8,6 @@ assertEq([3, 1, 4, 1], [3, 1, 4, 1])
 
 # Inequality
 assertNotEq(2, 3)
+
+assert(1 < 2)
+assert(1.0 < 2.0)