Add set index in list, and update lib+examples+tests

core/compiler.go

@@ -977,6 +977,41 @@ func (c *Compiler) compileAssignFromStack(to Node, sig TypeSignature, declare bo
 		}
 
 		return sig, nil
+	case IndexNodeType:
+		if declare {
+			return nil, c.error(fmt.Sprintf("cannot declare an indexed item"), to)
+		}
+
+		n := to.(*IndexNode)
+
+		ssig, err := c.compile(n.source)
+		if err != nil {
+			return nil, err
+		}
+
+		isig, err := c.compile(n.index)
+		if err != nil {
+			return nil, err
+		}
+
+		if isig.Type() != TypeInteger {
+			return nil, c.error(fmt.Sprintf("cannot index into list with non-integer (%s)", isig), n.index)
+		}
+
+		switch ssig.Type() {
+		case TypeList:
+			lsig := ssig.(*ListSignature)
+			if !c.typeMatches(sig, lsig.Contents) {
+				return nil, c.error(fmt.Sprintf("cannot assign value of type %s to list with items of type %s", sig, lsig.Contents), to)
+			}
+
+			c.add(InstructionSetIndexList)
+		default:
+			return nil, c.error(fmt.Sprintf("cannot set index of %s", ssig.Type()), n.source)
+		}
+
+		return sig, nil
+
 	default:
 		return nil, c.error(fmt.Sprintf("cannot assign to %s", to.Type()), to)
 	}