diff --git a/parser.go b/parser.go
index 19d46e8..e61d80b 100644
--- a/parser.go
+++ b/parser.go
@@ -18,13 +18,13 @@ func NewParser() (p *parser) {
 	return p
 }
 
-func (self *parser) parseFuncCall(scanner *scanner, allowVarRef bool, tk *Token) (tree *term, err error) {
+func (parser *parser) parseFuncCall(scanner *scanner, allowVarRef bool, tk *Token) (tree *term, err error) {
 	args := make([]*term, 0, 10)
 	itemExpected := false
 	lastSym := SymUnknown
 	for lastSym != SymClosedRound && lastSym != SymEos {
 		var subTree *ast
-		if subTree, err = self.parseItem(scanner, allowVarRef, SymComma, SymClosedRound); err != nil {
+		if subTree, err = parser.parseItem(scanner, allowVarRef, SymComma, SymClosedRound); err != nil {
 			break
 		}
 		prev := scanner.Previous()
@@ -48,7 +48,7 @@ func (self *parser) parseFuncCall(scanner *scanner, allowVarRef bool, tk *Token)
 	return
 }
 
-func (self *parser) parseFuncDef(scanner *scanner) (tree *term, err error) {
+func (parser *parser) parseFuncDef(scanner *scanner) (tree *term, err error) {
 	// Example: "add = func(x,y) {x+y}
 	var body *ast
 	args := make([]*term, 0)
@@ -65,7 +65,7 @@ func (self *parser) parseFuncDef(scanner *scanner) (tree *term, err error) {
 			if tk.Sym == SymEqual {
 				var paramExpr *ast
 				defaultParamsStarted = true
-				if paramExpr, err = self.parseItem(scanner, false, SymComma, SymClosedRound); err != nil {
+				if paramExpr, err = parser.parseItem(scanner, false, SymComma, SymClosedRound); err != nil {
 					break
 				}
 				param.forceChild(paramExpr.root)
@@ -88,7 +88,7 @@ func (self *parser) parseFuncDef(scanner *scanner) (tree *term, err error) {
 	if err == nil {
 		tk = scanner.Next()
 		if tk.IsSymbol(SymOpenBrace) {
-			body, err = self.parseGeneral(scanner, true, true, SymClosedBrace)
+			body, err = parser.parseGeneral(scanner, true, true, SymClosedBrace)
 		} else {
 			err = tk.ErrorExpectedGot("{")
 		}
@@ -104,7 +104,7 @@ func (self *parser) parseFuncDef(scanner *scanner) (tree *term, err error) {
 	return
 }
 
-func (self *parser) parseList(scanner *scanner, parsingIndeces bool, allowVarRef bool) (subtree *term, err error) {
+func (parser *parser) parseList(scanner *scanner, parsingIndeces bool, allowVarRef bool) (subtree *term, err error) {
 	r, c := scanner.lastPos()
 	args := make([]*term, 0)
 	lastSym := SymUnknown
@@ -112,7 +112,7 @@ func (self *parser) parseList(scanner *scanner, parsingIndeces bool, allowVarRef
 	for lastSym != SymClosedSquare && lastSym != SymEos {
 		var subTree *ast
 		zeroRequired := scanner.current.Sym == SymColon
-		if subTree, err = self.parseItem(scanner, allowVarRef, SymComma, SymClosedSquare); err == nil {
+		if subTree, err = parser.parseItem(scanner, allowVarRef, SymComma, SymClosedSquare); err == nil {
 			root := subTree.root
 			if root != nil {
 				if !parsingIndeces && root.symbol() == SymColon {
@@ -153,14 +153,14 @@ func (self *parser) parseList(scanner *scanner, parsingIndeces bool, allowVarRef
 	return
 }
 
-func (self *parser) parseIterDef(scanner *scanner, allowVarRef bool) (subtree *term, err error) {
+func (parser *parser) parseIterDef(scanner *scanner, allowVarRef bool) (subtree *term, err error) {
 	tk := scanner.Previous()
 	args := make([]*term, 0)
 	lastSym := SymUnknown
 	itemExpected := false
 	for lastSym != SymClosedRound && lastSym != SymEos {
 		var subTree *ast
-		if subTree, err = self.parseItem(scanner, allowVarRef, SymComma, SymClosedRound); err == nil {
+		if subTree, err = parser.parseItem(scanner, allowVarRef, SymComma, SymClosedRound); err == nil {
 			if subTree.root != nil {
 				args = append(args, subTree.root)
 			} else if itemExpected {
@@ -184,7 +184,7 @@ func (self *parser) parseIterDef(scanner *scanner, allowVarRef bool) (subtree *t
 	return
 }
 
-func (self *parser) parseDictKey(scanner *scanner, allowVarRef bool) (key any, err error) {
+func (parser *parser) parseDictKey(scanner *scanner, allowVarRef bool) (key any, err error) {
 	tk := scanner.Next()
 	if tk.Sym == SymError {
 		err = tk.Error()
@@ -206,14 +206,14 @@ func (self *parser) parseDictKey(scanner *scanner, allowVarRef bool) (key any, e
 	return
 }
 
-func (self *parser) parseDictionary(scanner *scanner, allowVarRef bool) (subtree *term, err error) {
+func (parser *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 {
+		if key, err = parser.parseDictKey(scanner, allowVarRef); err != nil {
 			break
 		} else if key == nil {
 			tk := scanner.Previous()
@@ -223,10 +223,10 @@ func (self *parser) parseDictionary(scanner *scanner, allowVarRef bool) (subtree
 			}
 			break
 		}
-		if subTree, err = self.parseItem(scanner, allowVarRef, SymComma, SymClosedBrace); err == nil {
+		if subTree, err = parser.parseItem(scanner, allowVarRef, SymComma, SymClosedBrace); err == nil {
 			if subTree.root != nil {
 				args[key] = subTree.root
-			} else if key != nil {
+			} else /*if key != nil*/ {
 				prev := scanner.Previous()
 				err = prev.ErrorExpectedGot("dictionary-value")
 				break
@@ -248,7 +248,7 @@ func (self *parser) parseDictionary(scanner *scanner, allowVarRef bool) (subtree
 	return
 }
 
-func (self *parser) parseSelectorCase(scanner *scanner, allowVarRef bool, defaultCase bool) (caseTerm *term, err error) {
+func (parser *parser) parseSelectorCase(scanner *scanner, allowVarRef bool, defaultCase bool) (caseTerm *term, err error) {
 	var filterList *term
 	var caseExpr *ast
 	tk := scanner.Next()
@@ -259,7 +259,7 @@ func (self *parser) parseSelectorCase(scanner *scanner, allowVarRef bool, defaul
 			err = tk.Errorf("case list in default clause")
 			return
 		}
-		if filterList, err = self.parseList(scanner, false, allowVarRef); err != nil {
+		if filterList, err = parser.parseList(scanner, false, allowVarRef); err != nil {
 			return
 		}
 		tk = scanner.Next()
@@ -270,7 +270,7 @@ func (self *parser) parseSelectorCase(scanner *scanner, allowVarRef bool, defaul
 	}
 
 	if tk.Sym == SymOpenBrace {
-		if caseExpr, err = self.parseGeneral(scanner, true, allowVarRef, SymClosedBrace); err != nil {
+		if caseExpr, err = parser.parseGeneral(scanner, true, allowVarRef, SymClosedBrace); err != nil {
 			return
 		}
 	} else {
@@ -296,25 +296,25 @@ func addSelectorCase(selectorTerm, caseTerm *term) {
 	caseTerm.parent = selectorTerm
 }
 
-func (self *parser) parseSelector(scanner *scanner, tree *ast, allowVarRef bool) (selectorTerm *term, err error) {
+func (parser *parser) parseSelector(scanner *scanner, tree *ast, allowVarRef bool) (selectorTerm *term, err error) {
 	var caseTerm *term
 	tk := scanner.makeToken(SymSelector, '?')
 	if selectorTerm, err = tree.addToken2(tk); err != nil {
 		return
 	}
 
-	if caseTerm, err = self.parseSelectorCase(scanner, allowVarRef, false); err == nil {
+	if caseTerm, err = parser.parseSelectorCase(scanner, allowVarRef, false); err == nil {
 		addSelectorCase(selectorTerm, caseTerm)
 	}
 	return
 }
 
-func (self *parser) parseItem(scanner *scanner, allowVarRef bool, termSymbols ...Symbol) (tree *ast, err error) {
-	return self.parseGeneral(scanner, false, allowVarRef, termSymbols...)
+func (parser *parser) parseItem(scanner *scanner, allowVarRef bool, termSymbols ...Symbol) (tree *ast, err error) {
+	return parser.parseGeneral(scanner, false, allowVarRef, termSymbols...)
 }
 
-func (self *parser) Parse(scanner *scanner, termSymbols ...Symbol) (tree *ast, err error) {
-	return self.parseGeneral(scanner, true, false, termSymbols...)
+func (parser *parser) Parse(scanner *scanner, termSymbols ...Symbol) (tree *ast, err error) {
+	return parser.parseGeneral(scanner, true, false, termSymbols...)
 }
 
 func couldBeACollection(t *term) bool {
@@ -333,7 +333,7 @@ func couldBeACollection(t *term) bool {
 // 	return areOut
 // }
 
-func (self *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarRef bool, termSymbols ...Symbol) (tree *ast, err error) {
+func (parser *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarRef bool, termSymbols ...Symbol) (tree *ast, err error) {
 	var selectorTerm *term = nil
 	var currentTerm *term = nil
 	var tk *Token
@@ -371,21 +371,21 @@ func (self *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarRef
 		switch tk.Sym {
 		case SymOpenRound:
 			var subTree *ast
-			if subTree, err = self.parseGeneral(scanner, false, allowVarRef, SymClosedRound); err == nil {
+			if subTree, err = parser.parseGeneral(scanner, false, allowVarRef, SymClosedRound); err == nil {
 				subTree.root.priority = priValue
 				err = tree.addTerm(newExprTerm(subTree.root))
 				currentTerm = subTree.root
 			}
 		case SymFuncCall:
 			var funcCallTerm *term
-			if funcCallTerm, err = self.parseFuncCall(scanner, allowVarRef, tk); err == nil {
+			if funcCallTerm, err = parser.parseFuncCall(scanner, allowVarRef, tk); err == nil {
 				err = tree.addTerm(funcCallTerm)
 				currentTerm = funcCallTerm
 			}
 		case SymOpenSquare:
 			var listTerm *term
 			parsingIndeces := couldBeACollection(currentTerm)
-			if listTerm, err = self.parseList(scanner, parsingIndeces, allowVarRef); err == nil {
+			if listTerm, err = parser.parseList(scanner, parsingIndeces, allowVarRef); err == nil {
 				if parsingIndeces {
 					indexTk := NewToken(listTerm.tk.row, listTerm.tk.col, SymIndex, listTerm.source())
 					indexTerm := newTerm(indexTk)
@@ -402,7 +402,7 @@ func (self *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarRef
 				err = currentTerm.Errorf(`selector-case outside of a selector context`)
 			} else {
 				var mapTerm *term
-				if mapTerm, err = self.parseDictionary(scanner, allowVarRef); err == nil {
+				if mapTerm, err = parser.parseDictionary(scanner, allowVarRef); err == nil {
 					err = tree.addTerm(mapTerm)
 					currentTerm = mapTerm
 				}
@@ -413,13 +413,13 @@ func (self *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarRef
 			// }
 		case SymFuncDef:
 			var funcDefTerm *term
-			if funcDefTerm, err = self.parseFuncDef(scanner); err == nil {
+			if funcDefTerm, err = parser.parseFuncDef(scanner); err == nil {
 				err = tree.addTerm(funcDefTerm)
 				currentTerm = funcDefTerm
 			}
 		case SymDollarRound:
 			var iterDefTerm *term
-			if iterDefTerm, err = self.parseIterDef(scanner, allowVarRef); err == nil {
+			if iterDefTerm, err = parser.parseIterDef(scanner, allowVarRef); err == nil {
 				err = tree.addTerm(iterDefTerm)
 				currentTerm = iterDefTerm
 			}
@@ -430,13 +430,13 @@ func (self *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarRef
 				currentTerm, err = tree.addToken2(tk)
 			}
 		case SymQuestion:
-			if selectorTerm, err = self.parseSelector(scanner, tree, allowVarRef); err == nil {
+			if selectorTerm, err = parser.parseSelector(scanner, tree, allowVarRef); err == nil {
 				currentTerm = selectorTerm
 			}
 		case SymColon, SymDoubleColon:
 			var caseTerm *term
 			if selectorTerm != nil {
-				if caseTerm, err = self.parseSelectorCase(scanner, allowVarRef, tk.Sym == SymDoubleColon); err == nil {
+				if caseTerm, err = parser.parseSelectorCase(scanner, allowVarRef, tk.Sym == SymDoubleColon); err == nil {
 					addSelectorCase(selectorTerm, caseTerm)
 					currentTerm = caseTerm
 					if tk.Sym == SymDoubleColon {