func-math.go/add: now supports the general iterator interface

ast.go

@@ -83,8 +83,9 @@ func (self *ast) insert(tree, node *term) (root *term, err error) {
 		if tree.isComplete() {
 			var subRoot *term
 			last := tree.removeLastChild()
-			subRoot, err = self.insert(last, node)
+			if subRoot, err = self.insert(last, node); err == nil {
 				subRoot.setParent(tree)
+			}
 		} else {
 			node.setParent(tree)
 		}

context.go

@@ -36,7 +36,7 @@ type ExprContext interface {
 	setVar(varName string, value any)
 	EnumVars(func(name string) (accept bool)) (varNames []string)
 	EnumFuncs(func(name string) (accept bool)) (funcNames []string)
-	GetFuncInfo(name string) ExprFunc
+	GetFuncInfo(name string) (item ExprFunc, exists bool)
 	Call(name string, args []any) (result any, err error)
 	RegisterFunc(name string, f Functor, minArgs, maxArgs int)
 }

expr_test.go

@@ -21,6 +21,7 @@ func TestExpr(t *testing.T) {
 		/*   1 */ {`0?{}`, nil, nil},
 		/*   2 */ {`fact=func(n){(n)?{1}::{n*fact(n-1)}}; fact(5)`, int64(120), nil},
 		/*   3 */ {`f=openFile("test-file.txt"); line=readFile(f); closeFile(f); line`, "uno", nil},
+		/*   4 */ {`mynot=func(v){int(v)?{true}::{false}}; mynot(0)`, true, nil},
 	}
 
 	succeeded := 0

func-builtins.go

@@ -45,6 +45,10 @@ func intFunc(ctx ExprContext, name string, args []any) (result any, err error) {
 	return
 }
 
+func iteratorFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+	return
+}
+
 func ImportBuiltinsFuncs(ctx ExprContext) {
 	ctx.RegisterFunc("isNil", &simpleFunctor{f: isNilFunc}, 1, -1)
 	ctx.RegisterFunc("int", &simpleFunctor{f: intFunc}, 1, -1)

func-import.go

@@ -140,3 +140,7 @@ func ImportImportFuncs(ctx ExprContext) {
 	ctx.RegisterFunc("import", &simpleFunctor{f: importFunc}, 1, -1)
 	ctx.RegisterFunc("include", &simpleFunctor{f: includeFunc}, 1, -1)
 }
+
+func init() {
+	registerImport("import", ImportImportFuncs)
+}

func-math.go

@@ -23,15 +23,20 @@ func doAdd(ctx ExprContext, name string, it Iterator) (result any, err error) {
 	var v any
 
 	for v, err = it.Next(); err == nil; v, err = it.Next() {
+		if subIter, ok := v.(Iterator); ok {
+			if v, err = doAdd(ctx, name, subIter); err != nil {
+				break
+			}
+		} else {
 			if err = checkNumberParamExpected(name, v, it.Index()); err != nil {
 				break
 			}
-
 			if array, ok := v.([]any); ok {
 				if v, err = doAdd(ctx, name, NewFlatArrayIterator(array)); err != nil {
 					break
 				}
 			}
+		}
 
 		if !sumAsFloat && isFloat(v) {
 			sumAsFloat = true

func-os.go

@@ -162,3 +162,7 @@ func ImportOsFuncs(ctx ExprContext) {
 	ctx.RegisterFunc("readFile", &simpleFunctor{f: readFileFunc}, 1, 2)
 	ctx.RegisterFunc("closeFile", &simpleFunctor{f: closeFileFunc}, 1, 1)
 }
+
+func init() {
+	registerImport("os", ImportOsFuncs)
+}

iter-list.go

@@ -0,0 +1,42 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// iter-list.go
+package expr
+
+import "io"
+
+type FlatArrayIterator struct {
+	a     []any
+	index int
+}
+
+func NewFlatArrayIterator(array []any) *FlatArrayIterator {
+	return &FlatArrayIterator{a: array, index: 0}
+}
+
+func (it *FlatArrayIterator) Current() (item any, err error) {
+	if it.index >= 0 && it.index < len(it.a) {
+		item = it.a[it.index]
+	} else {
+		err = io.EOF
+	}
+	return
+}
+
+func (it *FlatArrayIterator) Next() (item any, err error) {
+	if item, err = it.Current(); err != io.EOF {
+		it.index++
+	}
+	// if it.index < len(it.a) {
+	// 	item = it.a[it.index]
+	// 	it.index++
+	// } else {
+	// 	err = io.EOF
+	// }
+	return
+}
+
+func (it *FlatArrayIterator) Index() int {
+	return it.index - 1
+}

iterator.go

@@ -4,37 +4,8 @@
 // iterator.go
 package expr
 
-import "io"
-
 type Iterator interface {
-	Reset()
 	Next() (item any, err error) // must return io.EOF after the last item
+	Current() (item any, err error)
 	Index() int
 }
-
-type FlatArrayIterator struct {
-	a     []any
-	index int
-}
-
-func NewFlatArrayIterator(array []any) *FlatArrayIterator {
-	return &FlatArrayIterator{a: array, index: 0}
-}
-
-func (it *FlatArrayIterator) Reset() {
-	it.index = 0
-}
-
-func (it *FlatArrayIterator) Next() (item any, err error) {
-	if it.index < len(it.a) {
-		item = it.a[it.index]
-		it.index++
-	} else {
-		err = io.EOF
-	}
-	return
-}
-
-func (it *FlatArrayIterator) Index() int {
-	return it.index - 1
-}

operand-dict.go

@@ -0,0 +1,38 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operand-dict.go
+package expr
+
+// -------- dict term
+// func newDictTermA(args ...*term) *term {
+// 	return newDictTerm(args)
+// }
+
+func newDictTerm(args map[any]*term) *term {
+	return &term{
+		tk:       *NewValueToken(0, 0, SymDict, "{}", args),
+		parent:   nil,
+		children: nil,
+		position: posLeaf,
+		priority: priValue,
+		evalFunc: evalDict,
+	}
+}
+
+// -------- dict func
+func evalDict(ctx ExprContext, self *term) (v any, err error) {
+	dict, _ := self.value().(map[any]*term)
+	items := make(map[any]any, len(dict))
+	for key, tree := range dict {
+		var param any
+		if param, err = tree.compute(ctx); err != nil {
+			break
+		}
+		items[key] = param
+	}
+	if err == nil {
+		v = items
+	}
+	return
+}

operand-func.go

@@ -12,8 +12,6 @@ import (
 func newFuncCallTerm(tk *Token, args []*term) *term {
 	return &term{
 		tk:       *tk,
-		// class:    classVar,
-		// kind:     kindUnknown,
 		parent:   nil,
 		children: args,
 		position: posLeaf,
@@ -44,7 +42,7 @@ func evalFuncCall(parentCtx ExprContext, self *term) (v any, err error) {
 			}
 			// Export functions
 			for _, refName := range ctx.EnumFuncs(func(name string) bool { return exportAll || name[0] == '@' }) {
-				if info := ctx.GetFuncInfo(refName); info != nil {
+				if info, _ := ctx.GetFuncInfo(refName); info != nil {
 					exportFunc(parentCtx, refName, info)
 				}
 			}

operand-iterator.go

@@ -0,0 +1,152 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operand-iterator.go
+package expr
+
+import (
+	"fmt"
+	"io"
+)
+
+// -------- iterator term
+
+const (
+	initName    = "init"
+	nextName    = "next"
+	currentName = "current"
+)
+
+type dataCursor struct {
+	ds          map[any]*term
+	ctx         ExprContext
+	index       int
+	resource    any
+	nextFunc    Functor
+	currentFunc Functor
+}
+
+func (dc *dataCursor) String() string {
+	var s string
+	if item, err := dc.Current(); err == nil {
+		s = fmt.Sprintf("%v", item)
+	} else {
+		s = "(nil)"
+	}
+	return s
+}
+
+func (dc *dataCursor) Current() (item any, err error) { // must return io.EOF at the last item
+	if item, err = dc.currentFunc.Invoke(dc.ctx, currentName, []any{}); err == nil && item == nil {
+		err = io.EOF
+	}
+	return
+}
+
+func (dc *dataCursor) Next() (item any, err error) { // must return io.EOF after the last item
+	if item, err = dc.nextFunc.Invoke(dc.ctx, nextName, []any{}); err == nil {
+		if item == nil {
+			err = io.EOF
+		} else {
+			dc.index++
+		}
+	}
+	return
+}
+
+func (dc *dataCursor) Index() int {
+	return dc.index
+}
+
+func newIteratorTerm(tk *Token, dsTerm *term, args []*term) *term {
+	tk.Sym = SymIterator
+
+	children := make([]*term, 0, 1+len(args))
+	children = append(children, dsTerm)
+	children = append(children, args...)
+	return &term{
+		tk:       *tk,
+		parent:   nil,
+		children: children,
+		position: posLeaf,
+		priority: priValue,
+		evalFunc: evalIterator,
+	}
+}
+
+// -------- eval iterator
+
+func evalTermArray(ctx ExprContext, a []*term) (values []any, err error) {
+	values = make([]any, len(a))
+	for i, t := range a {
+		var value any
+		if value, err = t.compute(ctx); err == nil {
+			values[i] = value
+		} else {
+			break
+		}
+	}
+	return
+}
+
+func getDataSourceDict(ctx ExprContext, self *term) (ds map[string]Functor, err error) {
+	var value any
+	if len(self.children) < 1 || self.children[0] == nil {
+		err = self.Errorf("missing the data-source parameter")
+		return
+	}
+
+	if value, err = self.children[0].compute(ctx); err != nil {
+		return
+	}
+
+	if dictAny, ok := value.(map[any]any); ok {
+		ds = make(map[string]Functor)
+		for _, k := range []string{initName, currentName, nextName} {
+			if item, exists := dictAny[k]; exists && item != nil {
+				if functor, ok := item.(*funcDefFunctor); ok {
+					ds[k] = functor
+				}
+			} else if k != initName {
+				err = fmt.Errorf("the data-source must provide a non-nil %q operator", k)
+				break
+			}
+		}
+	} else {
+		err = self.Errorf("the first param (data-source) of an iterator must be a dict, not a %T", value)
+	}
+	return
+}
+
+func evalIterator(ctx ExprContext, self *term) (v any, err error) {
+	var ds map[string]Functor
+
+	if ds, err = getDataSourceDict(ctx, self); err != nil {
+		return
+	}
+
+	dc := &dataCursor{
+		index: -1,
+		ctx:   ctx.Clone(),
+	}
+
+	if initFunc, exists := ds[initName]; exists && initFunc != nil {
+		var args []any
+		if len(self.children) > 1 {
+			if args, err = evalTermArray(ctx, self.children[1:]); err != nil {
+				return
+			}
+		} else {
+			args = []any{}
+		}
+		if dc.resource, err = initFunc.Invoke(dc.ctx, initName, args); err != nil {
+			return
+		}
+	}
+
+	dc.nextFunc, _ = ds[nextName]
+	dc.currentFunc, _ = ds[currentName]
+	v = dc
+
+	return
+}

operand-var.go

@@ -23,8 +23,13 @@ func newVarTerm(tk *Token) *term {
 // -------- eval func
 func evalVar(ctx ExprContext, self *term) (v any, err error) {
 	var exists bool
-	if v, exists = ctx.GetVar(self.tk.source); !exists {
+	name := self.source()
-		err = fmt.Errorf("undefined variable %q", self.tk.source)
+	if v, exists = ctx.GetVar(name); !exists {
+		if info, exists := ctx.GetFuncInfo(name); exists {
+			v = info.Functor()
+		} else {
+			err = fmt.Errorf("undefined variable or function %q", name)
+		}
 	}
 	return
 }

operator-assign.go

@@ -31,7 +31,7 @@ func evalAssign(ctx ExprContext, self *term) (v any, err error) {
 		if functor, ok := v.(Functor); ok {
 			ctx.RegisterFunc(leftTerm.source(), functor, 0, -1)
 		} else {
-			ctx.setVar(leftTerm.tk.source, v)
+			ctx.setVar(leftTerm.source(), v)
 		}
 	}
 	return

operator-coalesce.go

@@ -34,11 +34,11 @@ func evalNullCoalesce(ctx ExprContext, self *term) (v any, err error) {
 	if leftValue, exists := ctx.GetVar(leftTerm.source()); exists {
 		v = leftValue
 	} else if rightValue, err = self.children[1].compute(ctx); err == nil {
-		if _, ok := rightValue.(Functor); ok {
+		// if _, ok := rightValue.(Functor); ok {
-			err = errCoalesceNoFunc(self.children[1])
+		// 	err = errCoalesceNoFunc(self.children[1])
-		} else {
+		// } else {
 		v = rightValue
-		}
+		// }
 	}
 	return
 }
@@ -71,8 +71,8 @@ func evalAssignCoalesce(ctx ExprContext, self *term) (v any, err error) {
 	if leftValue, exists := ctx.GetVar(leftTerm.source()); exists {
 		v = leftValue
 	} else if rightValue, err = self.children[1].compute(ctx); err == nil {
-		if _, ok := rightValue.(Functor); ok {
+		if functor, ok := rightValue.(Functor); ok {
-			err = errCoalesceNoFunc(self.children[1])
+			ctx.RegisterFunc(leftTerm.source(), functor, 0, -1)
 		} else {
 			v = rightValue
 			ctx.setVar(leftTerm.source(), rightValue)
@@ -82,9 +82,9 @@ func evalAssignCoalesce(ctx ExprContext, self *term) (v any, err error) {
 }
 
 // utils
-func errCoalesceNoFunc(t *term) error {
+// func errCoalesceNoFunc(t *term) error {
-	return t.Errorf("the right operand of a coalescing operation cannot be a function definition")
+// 	return t.Errorf("the right operand of a coalescing operation cannot be a function definition")
-}
+// }
 
 // init
 func init() {

operator-dot.go

@@ -4,6 +4,8 @@
 // operator-dot.go
 package expr
 
+import "fmt"
+
 // -------- dot term
 func newDotTerm(tk *Token) (inst *term) {
 	return &term{
@@ -23,15 +25,13 @@ func evalDot(ctx ExprContext, self *term) (v any, err error) {
 	}
 
 	indexTerm := self.children[1]
-	if !isInteger(rightValue) {
+
-		err = indexTerm.Errorf("index expression must be integer, got %T", rightValue)
+	if isList(leftValue) {
+		var index int
+		if index, err = indexTerm.toInt(rightValue, "index expression value must be integer"); err != nil {
 			return
 		}
 
-	index64, _ := rightValue.(int64)
-	index := int(index64)
-
-	if isList(leftValue) {
 		list, _ := leftValue.([]any)
 		if index >= 0 && index < len(list) {
 			v = list[index]
@@ -41,6 +41,11 @@ func evalDot(ctx ExprContext, self *term) (v any, err error) {
 			err = indexTerm.Errorf("index %v out of bounds", index)
 		}
 	} else if isString(leftValue) {
+		var index int
+		if index, err = indexTerm.toInt(rightValue, "index expression value must be integer"); err != nil {
+			return
+		}
+
 		s, _ := leftValue.(string)
 		if index >= 0 && index < len(s) {
 			v = string(s[index])
@@ -49,6 +54,12 @@ func evalDot(ctx ExprContext, self *term) (v any, err error) {
 		} else {
 			err = indexTerm.Errorf("index %v out of bounds", index)
 		}
+	} else if isDict(leftValue) {
+		var ok bool
+		d, _ := leftValue.(map[any]any)
+		if v, ok = d[rightValue]; !ok {
+			err = fmt.Errorf("key %v does not belong to the dictionary", rightValue)
+		}
 	} else {
 		err = self.errIncompatibleTypes(leftValue, rightValue)
 	}

operator-iter-value.go

@@ -0,0 +1,38 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-iter-value.go
+package expr
+
+
+//-------- iter value term
+
+func newIterValueTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 1),
+		position: posPrefix,
+		priority: priIterValue,
+		evalFunc: evalIterValue,
+	}
+}
+
+func evalIterValue(ctx ExprContext, self *term) (v any, err error) {
+	var leftValue any
+
+	if leftValue, err = self.evalPrefix(ctx); err != nil {
+		return
+	}
+
+	if dc, ok := leftValue.(*dataCursor); ok {
+		v, err = dc.Current()
+	} else {
+		err = self.errIncompatibleType(leftValue)
+	}
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymOpenClosedRound, newIterValueTerm)
+}

operator-post-inc.go

@@ -0,0 +1,41 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-post-inc.go
+package expr
+
+// -------- post increment term
+
+func newPostIncTerm(tk *Token) *term {
+	return &term{
+		tk:       *tk,
+		parent:   nil,
+		children: make([]*term, 0, 1),
+		position: posPostfix,
+		priority: priPrePost,
+		evalFunc: evalPostInc,
+	}
+}
+
+func evalPostInc(ctx ExprContext, self *term) (v any, err error) {
+	var leftValue any
+	if leftValue, err = self.evalPrefix(ctx); err != nil {
+		return
+	}
+
+	if dc, ok := leftValue.(*dataCursor); ok {
+		v, err = dc.Next()
+	} else if isInteger(leftValue) && self.children[0].symbol() == SymIdentifier {
+		v = leftValue
+		i, _ := leftValue.(int64)
+		ctx.SetVar(self.children[0].source(), i+1)
+	} else {
+		self.errIncompatibleType(leftValue)
+	}
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymDoublePlus, newPostIncTerm)
+}

parser.go

@@ -58,23 +58,72 @@ func (self *parser) parseFuncCall(scanner *scanner, allowVarRef bool, tk *Token)
 	return
 }
 
+// func (self *parser) parseFuncDef(scanner *scanner) (tree *term, err error) {
+// 	// Example: "add = func(x,y) {x+y}
+// 	var body *ast
+// 	args := make([]*term, 0)
+// 	tk := scanner.Next()
+// 	for tk.Sym != SymClosedRound && tk.Sym != SymEos {
+// 		if tk.Sym == SymIdentifier {
+// 			t := newTerm(tk, nil)
+// 			args = append(args, t)
+// 		} else {
+// 			err = tk.Errorf("invalid param %q, variable identifier expected", tk.source)
+// 			break
+// 		}
+// 		tk = scanner.Next()
+// 	}
+// 	if err == nil && tk.Sym != SymClosedRound {
+// 		err = tk.Errorf("unterminate function params list")
+// 	}
+// 	if err == nil {
+// 		tk = scanner.Next()
+// 		if tk.Sym == SymOpenBrace {
+// 			body, err = self.parseGeneral(scanner, true, true, SymClosedBrace)
+// 		}
+// 	}
+// 	if err == nil {
+// 		// TODO Check arguments
+// 		if scanner.Previous().Sym != SymClosedBrace {
+// 			err = scanner.Previous().Errorf("not properly terminated function body")
+// 		} else {
+// 			tk = scanner.makeValueToken(SymExpression, "", body)
+// 			tree = newFuncDefTerm(tk, args)
+// 		}
+// 	}
+// 	return
+// }
+
 func (self *parser) parseFuncDef(scanner *scanner) (tree *term, err error) {
 	// Example: "add = func(x,y) {x+y}
 	var body *ast
 	args := make([]*term, 0)
-	tk := scanner.Next()
+	lastSym := SymUnknown
-	for tk.Sym != SymClosedRound && tk.Sym != SymEos {
+	itemExpected := false
-		if tk.Sym == SymIdentifier {
+	tk := scanner.Previous()
-			t := newTerm(tk, nil)
+	for lastSym != SymClosedRound && lastSym != SymEos {
-			args = append(args, t)
+		var subTree *ast
+		if subTree, err = self.parseItem(scanner, true, SymComma, SymClosedRound); err == nil {
+			if subTree.root != nil {
+				if subTree.root.symbol() == SymIdentifier {
+					args = append(args, subTree.root)
 				} else {
-			err = tk.Errorf("invalid param %q, variable identifier expected", tk.source)
+					err = tk.Errorf("exptected identifier, got %q", subTree.root)
+				}
+			} else if itemExpected {
+				prev := scanner.Previous()
+				err = prev.Errorf("expected function parameter, got %q", prev)
 				break
 			}
-		tk = scanner.Next()
+		} else {
+			break
 		}
-	if err == nil && tk.Sym != SymClosedRound {
+		lastSym = scanner.Previous().Sym
-		err = tk.Errorf("unterminate function params list")
+		itemExpected = lastSym == SymComma
+	}
+
+	if err == nil && lastSym != SymClosedRound {
+		err = tk.Errorf("unterminated function parameters list")
 	}
 	if err == nil {
 		tk = scanner.Next()
@@ -97,16 +146,22 @@ func (self *parser) parseFuncDef(scanner *scanner) (tree *term, err error) {
 func (self *parser) parseList(scanner *scanner, allowVarRef bool) (subtree *term, err error) {
 	args := make([]*term, 0)
 	lastSym := SymUnknown
+	itemExpected := false
 	for lastSym != SymClosedSquare && lastSym != SymEos {
 		var subTree *ast
 		if subTree, err = self.parseItem(scanner, allowVarRef, SymComma, SymClosedSquare); err == nil {
 			if subTree.root != nil {
 				args = append(args, subTree.root)
+			} else if itemExpected {
+				prev := scanner.Previous()
+				err = prev.Errorf("expected list item, got %q", prev)
+				break
 			}
 		} else {
 			break
 		}
 		lastSym = scanner.Previous().Sym
+		itemExpected = lastSym == SymComma
 	}
 	if err == nil {
 		// TODO Check arguments
@@ -119,6 +174,115 @@ func (self *parser) parseList(scanner *scanner, allowVarRef bool) (subtree *term
 	return
 }
 
+func (self *parser) parseIterDef(scanner *scanner, allowVarRef bool) (subtree *term, err error) {
+	var ds *term
+	tk := scanner.Previous()
+	args := make([]*term, 0)
+	lastSym := SymUnknown
+	dsExpected := true
+	itemExpected := false
+	for lastSym != SymClosedRound && lastSym != SymEos {
+		var subTree *ast
+		if subTree, err = self.parseItem(scanner, allowVarRef, SymComma, SymClosedRound); err == nil {
+			if subTree.root != nil {
+				if dsExpected {
+					if sym := subTree.root.symbol(); sym == SymDict || sym == SymIdentifier {
+						ds = subTree.root
+					} else {
+						err = subTree.root.Errorf("data-source dictionary expected, got %q", subTree.root.source())
+					}
+					dsExpected = false
+				} else {
+					args = append(args, subTree.root)
+				}
+			} else if itemExpected {
+				prev := scanner.Previous()
+				err = prev.Errorf("expected iterator argument, got %q", prev)
+				break
+			}
+		} else {
+			break
+		}
+		lastSym = scanner.Previous().Sym
+		itemExpected = lastSym == SymComma
+	}
+	if err == nil {
+		// TODO Check arguments
+		if lastSym != SymClosedRound {
+			err = scanner.Previous().Errorf("unterminate iterator param list")
+		} else if ds != nil {
+			subtree = newIteratorTerm(tk, ds, args)
+		} else {
+			tk.Errorf("missing data-source param")
+		}
+	}
+	return
+}
+
+func (self *parser) parseDictKey(scanner *scanner, allowVarRef bool) (key any, err error) {
+	tk := scanner.Next()
+	if tk.Sym == SymError {
+		err = tk.Error()
+		return
+	}
+	if tk.Sym == SymClosedBrace || tk.Sym == SymEos {
+		return
+	}
+	if tk.Sym == SymInteger || tk.Sym == SymString {
+		tkSep := scanner.Next()
+		if tkSep.Sym != SymColon {
+			err = tkSep.Errorf("expected \":\", got %q", tkSep)
+		} else {
+			key = tk.Value
+		}
+	} else {
+		err = tk.Errorf("expected dictionary key or closed brace, got %q", tk)
+	}
+	return
+}
+
+func (self *parser) parseDictionary(scanner *scanner, allowVarRef bool) (subtree *term, err error) {
+	args := make(map[any]*term, 0)
+	lastSym := SymUnknown
+	itemExpected := false
+	for lastSym != SymClosedBrace && lastSym != SymEos {
+		var subTree *ast
+		var key any
+		if key, err = self.parseDictKey(scanner, allowVarRef); err != nil {
+			break
+		} else if key == nil {
+			tk := scanner.Previous()
+			lastSym = tk.Sym
+			if itemExpected {
+				err = tk.Errorf("expected dictionary key, got %q", tk)
+			}
+			break
+		}
+		if subTree, err = self.parseItem(scanner, allowVarRef, SymComma, SymClosedBrace); err == nil {
+			if subTree.root != nil {
+				args[key] = subTree.root
+			} else if key != nil {
+				prev := scanner.Previous()
+				err = prev.Errorf("expected dictionary value, got %q", prev)
+				break
+			}
+		} else {
+			break
+		}
+		lastSym = scanner.Previous().Sym
+		itemExpected = lastSym == SymComma
+	}
+	if err == nil {
+		// TODO Check arguments
+		if lastSym != SymClosedBrace {
+			err = scanner.Previous().Errorf("unterminated dictionary")
+		} else {
+			subtree = newDictTerm(args)
+		}
+	}
+	return
+}
+
 func (self *parser) parseSelectorCase(scanner *scanner, allowVarRef bool, defaultCase bool) (caseTerm *term, err error) {
 	var filterList *term
 	var caseExpr *ast
@@ -241,6 +405,12 @@ func (self *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarRef
 				err = tree.addTerm(listTerm)
 				currentTerm = listTerm
 			}
+		case SymOpenBrace:
+			var mapTerm *term
+			if mapTerm, err = self.parseDictionary(scanner, allowVarRef); err == nil {
+				err = tree.addTerm(mapTerm)
+				currentTerm = mapTerm
+			}
 		case SymEqual:
 			if err = checkPrevSymbol(lastSym, SymIdentifier, tk); err == nil {
 				currentTerm, err = tree.addToken2(tk)
@@ -251,6 +421,12 @@ func (self *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarRef
 				err = tree.addTerm(funcDefTerm)
 				currentTerm = funcDefTerm
 			}
+		case SymDollarRound:
+			var iterDefTerm *term
+			if iterDefTerm, err = self.parseIterDef(scanner, allowVarRef); err == nil {
+				err = tree.addTerm(iterDefTerm)
+				currentTerm = iterDefTerm
+			}
 		case SymIdentifier:
 			if tk.source[0] == '@' && !allowVarRef {
 				err = tk.Errorf("variable references are not allowed in top level expressions: %q", tk.source)

parser_test.go

@@ -7,6 +7,7 @@ package expr
 import (
 	"errors"
 	"fmt"
+	"reflect"
 	"strings"
 	"testing"
 )
@@ -117,9 +118,9 @@ func TestParser(t *testing.T) {
 		/*  96 */ {`x=2 but x*10`, int64(20), nil},
 		/*  97 */ {`false and true`, false, nil},
 		/*  98 */ {`false and (x==2)`, false, nil},
-		/*  99 */ {`false and (x=2 but x==2) or x==2`, nil, errors.New(`undefined variable "x"`)},
+		/*  99 */ {`false and (x=2 but x==2) or x==2`, nil, errors.New(`undefined variable or function "x"`)},
 		/* 100 */ {`false or true`, true, nil},
-		/* 101 */ {`false or (x==2)`, nil, errors.New(`undefined variable "x"`)},
+		/* 101 */ {`false or (x==2)`, nil, errors.New(`undefined variable or function "x"`)},
 		/* 102 */ {`a=5; a`, int64(5), nil},
 		/* 103 */ {`a=5; b=2; add(a, b*3)`, int64(11), nil},
 		/* 104 */ {`2=5`, nil, errors.New(`assign operator ("=") must be preceded by a variable`)},
@@ -134,13 +135,13 @@ func TestParser(t *testing.T) {
 		/* 113 */ {`import("test-funcs.expr"); (double(3+a) + 1) * two()`, int64(34), nil},
 		/* 114 */ {`x ?? "default"`, "default", nil},
 		/* 115 */ {`x="hello"; x ?? "default"`, "hello", nil},
-		/* 116 */ {`x ?? func(){}`, nil, errors.New(`[1:14] the right operand of a coalescing operation cannot be a function definition`)},
+		/* 116 */ {`y=x ?? func(){4}; y()`, int64(4), nil},
 		/* 117 */ {`x ?= "default"; x`, "default", nil},
 		/* 118 */ {`x="hello"; x ?= "default"; x`, "hello", nil},
 		/* 119 */ {`@x="hello"; @x`, nil, errors.New(`[1:3] variable references are not allowed in top level expressions: "@x"`)},
 		/* 120 */ {`f=func(){@x="hello"}; f(); x`, "hello", nil},
 		/* 121 */ {`f=func(@y){@y=@y+1}; f(2); y`, int64(3), nil},
-		/* 122 */ {`f=func(@y){g=func(){@x=5}; @y=@y+g()}; f(2); y+x`, nil, errors.New(`undefined variable "x"`)},
+		/* 122 */ {`f=func(@y){g=func(){@x=5}; @y=@y+g()}; f(2); y+x`, nil, errors.New(`undefined variable or function "x"`)},
 		/* 123 */ {`f=func(@y){g=func(){@x=5}; @z=g(); @y=@y+@z}; f(2); y+z`, int64(12), nil},
 		/* 124 */ {`f=func(@y){g=func(){@x=5}; g(); @z=x; @y=@y+@z}; f(2); y+z`, int64(12), nil},
 		/* 125 */ {`f=func(@y){g=func(){@x=5}; g(); @z=x; @x=@y+@z}; f(2); y+x`, int64(9), nil},
@@ -157,7 +158,11 @@ func TestParser(t *testing.T) {
 		/* 136 */ {`1 ? {"a"} : {"b"} ? ["a"] {"A"} :["b"] {"B"}`, "B", nil},
 		/* 137 */ {`2 + 1 ? {"a"} : {"b"} * 3`, "2bbb", nil},
 		/* 138 */ {`nil`, nil, nil},
-		/* 139 */ {`null`, nil, errors.New(`undefined variable "null"`)},
+		/* 139 */ {`null`, nil, errors.New(`undefined variable or function "null"`)},
+		/* 140 */ {`{"key"}`, nil, errors.New(`[1:8] expected ":", got "}"`)},
+		/* 141 */ {`{"key":}`, nil, errors.New(`[1:9] expected dictionary value, got "}"`)},
+		/* 142 */ {`{}`, map[any]any{}, nil},
+		/* 144 */ //{`3^2`, int64(9), nil},
 	}
 	check_env_expr_path := 113
 
@@ -165,7 +170,7 @@ func TestParser(t *testing.T) {
 	failed := 0
 
 	// inputs1 := []inputType{
-	// 	/* 140 */ {`isNil(nil)`, true, nil},
+	// 	/* 140 */ {`ds={}; $(ds)`, nil, nil},
 	// }
 
 	for i, input := range inputs {
@@ -190,7 +195,9 @@ func TestParser(t *testing.T) {
 			gotResult, gotErr = expr.Eval(ctx)
 		}
 
-		if gotResult != input.wantResult {
+		eq := reflect.DeepEqual(gotResult, input.wantResult)
+
+		if !eq /*gotResult != input.wantResult*/ {
 			t.Errorf("%d: %q -> result = %v [%T], want %v [%T]", i+1, input.source, gotResult, gotResult, input.wantResult, input.wantResult)
 			good = false
 		}
@@ -221,10 +228,6 @@ func TestListParser(t *testing.T) {
 		wantErr    error
 	}
 
-	// inputs1 := []inputType{
-	// 	{`add(1,2,3)`, int64(6), nil},
-	// }
-
 	inputs := []inputType{
 		/*  1 */ {`[]`, []any{}, nil},
 		/*  2 */ {`[1,2,3]`, []any{int64(1), int64(2), int64(3)}, nil},
@@ -244,6 +247,10 @@ func TestListParser(t *testing.T) {
 	succeeded := 0
 	failed := 0
 
+	// inputs1 := []inputType{
+	// 	/*  7 */ {`add([1,4,3,2])`, int64(10), nil},
+	// }
+
 	for i, input := range inputs {
 		var expr *ast
 		var gotResult any

scanner.go

@@ -86,13 +86,14 @@ func (self *scanner) Next() (tk *Token) {
 }
 
 func (self *scanner) fetchNextToken() (tk *Token) {
+	var ch byte
 	if err := self.skipBlanks(); err != nil {
 		return self.makeErrorToken(err)
 	}
 
 	escape := false
 	for {
-		ch, _ := self.readChar()
+		ch, _ = self.readChar()
 		switch ch {
 		case '+':
 			if next, _ := self.peek(); next == '+' {
@@ -143,6 +144,8 @@ func (self *scanner) fetchNextToken() (tk *Token) {
 			}
 		case ',':
 			tk = self.makeToken(SymComma, ch)
+		case '^':
+			tk = self.makeToken(SymCaret, ch)
 		case ':':
 			if next, _ := self.peek(); next == ':' {
 				tk = self.moveOn(SymDoubleColon, ch, next)
@@ -236,9 +239,18 @@ func (self *scanner) fetchNextToken() (tk *Token) {
 				tk = self.makeToken(SymGreater, ch)
 			}
 		case '$':
+			if next, _ := self.peek(); next == '(' {
+				tk = self.moveOn(SymDollarRound, ch, next)
+				tk.source += ")"
+			} else {
 				tk = self.makeToken(SymDollar, ch)
+			}
 		case '(':
+			if next, _ := self.peek(); next == ')' {
+				tk = self.moveOn(SymOpenClosedRound, ch, next)
+			} else {
 			tk = self.makeToken(SymOpenRound, ch)
+		}
 		case ')':
 			tk = self.makeToken(SymClosedRound, ch)
 		case '[':
@@ -271,6 +283,9 @@ func (self *scanner) fetchNextToken() (tk *Token) {
 			break
 		}
 	}
+	if tk == nil {
+		tk = NewErrorToken(self.row, self.column, fmt.Errorf("unknown symbol '%c'", ch))
+	}
 	return
 }
 

simple-func-store.go

@@ -50,8 +50,8 @@ func (ctx *SimpleFuncStore) Clone() ExprContext {
 	}
 }
 
-func (ctx *SimpleFuncStore) GetFuncInfo(name string) (info ExprFunc) {
+func (ctx *SimpleFuncStore) GetFuncInfo(name string) (info ExprFunc, exists bool) {
-	info, _ = ctx.funcStore[name]
+	info, exists = ctx.funcStore[name]
 	return
 }
 

simple-var-store.go

@@ -54,7 +54,7 @@ func (ctx *SimpleVarStore) EnumVars(acceptor func(name string) (accept bool)) (v
 	return
 }
 
-func (ctx *SimpleVarStore) GetFuncInfo(name string) (f ExprFunc) {
+func (ctx *SimpleVarStore) GetFuncInfo(name string) (f ExprFunc, exists bool) {
 	return
 }
 

symbol.go

@@ -61,6 +61,9 @@ const (
 	SymDoubleColon                       //  50: '::'
 	SymInsert                            //  51: '>>'
 	SymAppend                            //  52: '<<'
+	SymCaret                             //  53: '^'
+	SymDollarRound                       //  54: '$('
+	SymOpenClosedRound //  55: '()'
 	SymChangeSign
 	SymUnchangeSign
 	SymIdentifier
@@ -68,6 +71,7 @@ const (
 	SymInteger
 	SymFloat
 	SymString
+	SymIterator
 	SymOr
 	SymAnd
 	SymNot
@@ -75,6 +79,7 @@ const (
 	SymFuncCall
 	SymFuncDef
 	SymList
+	SymDict
 	SymExpression
 	SymSelector     // <selector> ::= <expr> "?" <selector-case> {":" <selector-case>} ["::" <default-selector-case>]
 	SymSelectorCase // <selector-case> ::= [<list>] "{" <multi-expr> "}"

term.go

@@ -23,7 +23,9 @@ const (
 	priSelector
 	priSign
 	priFact
+	priIterValue
 	priCoalesce
+	priPrePost
 	priDot
 	priValue
 )
@@ -127,6 +129,10 @@ func (self *term) setParent(parent *term) {
 	}
 }
 
+func (self *term) symbol() Symbol {
+	return self.tk.Sym
+}
+
 func (self *term) source() string {
 	return self.tk.source
 }
@@ -144,6 +150,15 @@ func (self *term) compute(ctx ExprContext) (v any, err error) {
 	return
 }
 
+func (self *term) toInt(computedValue any, valueDescription string) (i int, err error) {
+	if index64, ok := computedValue.(int64); ok {
+		i = int(index64)
+	} else {
+		err = self.Errorf("%s, got %T", valueDescription, computedValue)
+	}
+	return
+}
+
 func (self *term) errIncompatibleTypes(leftValue, rightValue any) error {
 	return self.tk.Errorf(
 		"left operand '%v' [%T] and right operand '%v' [%T] are not compatible with operator %q",

utils.go

@@ -26,6 +26,11 @@ func isList(v any) (ok bool) {
 	return ok
 }
 
+func isDict(v any) (ok bool) {
+	_, ok = v.(map[any]any)
+	return ok
+}
+
 func isNumber(v any) (ok bool) {
 	return isFloat(v) || isInteger(v)
 }