operator-post-inc.go: new post int decrement operator '--'

This feature is implemented by expansion, not by dedicated operators, e.g. a*=2+x is exapanded as a=a*(2+x)

ast.go

@@ -45,19 +45,19 @@ func (expr *ast) String() string {
 
 func (expr *ast) addTokens(tokens ...*Token) (err error) {
 	for _, tk := range tokens {
-		if err = expr.addToken(tk); err != nil {
+		if _, err = expr.addToken(tk); err != nil {
 			break
 		}
 	}
 	return
 }
 
-func (expr *ast) addToken(tk *Token) (err error) {
+// func (expr *ast) addToken(tk *Token) (err error) {
-	_, err = expr.addToken2(tk)
+// 	_, err = expr.addToken2(tk)
-	return
+// 	return
-}
+// }
 
-func (expr *ast) addToken2(tk *Token) (t *term, err error) {
+func (expr *ast) addToken(tk *Token) (t *term, err error) {
 	if t = newTerm(tk); t != nil {
 		err = expr.addTerm(t)
 	} else {

operator-post-inc.go

@@ -35,7 +35,39 @@ func evalPostInc(ctx ExprContext, opTerm *term) (v any, err error) {
 	return
 }
 
+// -------- post decrement term
+
+func newPostDecTerm(tk *Token) *term {
+	return &term{
+		tk:       *tk,
+		parent:   nil,
+		children: make([]*term, 0, 1),
+		position: posPostfix,
+		priority: priIncDec,
+		evalFunc: evalPostDec,
+	}
+}
+
+func evalPostDec(ctx ExprContext, opTerm *term) (v any, err error) {
+	var childValue any
+	if childValue, err = opTerm.evalPrefix(ctx); err != nil {
+		return
+	}
+
+	/* if it, ok := childValue.(Iterator); ok {
+		v, err = it.Next()
+	} else  */if IsInteger(childValue) && opTerm.children[0].symbol() == SymVariable {
+		v = childValue
+		i, _ := childValue.(int64)
+		ctx.SetVar(opTerm.children[0].source(), i-1)
+	} else {
+		err = opTerm.errIncompatibleType(childValue)
+	}
+	return
+}
+
 // init
 func init() {
 	registerTermConstructor(SymDoublePlus, newPostIncTerm)
+	registerTermConstructor(SymDoubleMinus, newPostDecTerm)
 }

parser.go

@@ -19,7 +19,8 @@ func NewParser() (p *parser) {
 }
 
 func (parser *parser) Next(scanner *scanner) (tk *Token) {
-	for tk=scanner.Next(); tk.IsSymbol(SymComment); tk=scanner.Next() {}
+	for tk = scanner.Next(); tk.IsSymbol(SymComment); tk = scanner.Next() {
+	}
 	return
 }
 
@@ -304,7 +305,7 @@ func addSelectorCase(selectorTerm, caseTerm *term) {
 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 {
+	if selectorTerm, err = tree.addToken(tk); err != nil {
 		return
 	}
 
@@ -342,13 +343,14 @@ func (parser *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarR
 	var selectorTerm *term = nil
 	var currentTerm *term = nil
 	var tk *Token
+
 	tree = NewAst()
 	firstToken := true
 	// lastSym := SymUnknown
 	for tk = parser.Next(scanner); err == nil && tk != nil && !tk.IsTerm(termSymbols); /*&& !areSymbolsOutOfCtx(tk, selectorTerm, SymColon, SymDoubleColon)*/ tk = parser.Next(scanner) {
-		if tk.Sym == SymComment {
+		// if tk.Sym == SymComment {
-			continue
+		// 	continue
-		}
+		// }
 
 		if tk.Sym == SymSemiColon {
 			if allowForest {
@@ -414,7 +416,7 @@ func (parser *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarR
 			}
 		case SymEqual:
 			// if err = checkPrevSymbol(lastSym, SymIdentifier, tk); err == nil {
-			currentTerm, err = tree.addToken2(tk)
+			currentTerm, err = tree.addToken(tk)
 			// }
 		case SymFuncDef:
 			var funcDefTerm *term
@@ -432,7 +434,7 @@ func (parser *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarR
 			if tk.source[0] == '@' && !allowVarRef {
 				err = tk.Errorf("variable references are not allowed in top level expressions: %q", tk.source)
 			} else {
-				currentTerm, err = tree.addToken2(tk)
+				currentTerm, err = tree.addToken(tk)
 			}
 		case SymQuestion:
 			if selectorTerm, err = parser.parseSelector(scanner, tree, allowVarRef); err == nil {
@@ -449,14 +451,16 @@ func (parser *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarR
 					}
 				}
 			} else {
-				currentTerm, err = tree.addToken2(tk)
+				currentTerm, err = tree.addToken(tk)
 			}
 			if tk.IsSymbol(SymColon) {
 				// Colon outside a selector term acts like a separator
 				firstToken = true
 			}
+		case SymPlusEqual, SymMinusEqual, SymStarEqual:
+			currentTerm, err = parser.expandOpAssign(scanner, tree, tk, allowVarRef)
 		default:
-			currentTerm, err = tree.addToken2(tk)
+			currentTerm, err = tree.addToken(tk)
 		}
 
 		if currentTerm != nil && currentTerm.tk.Sym != SymSelector && currentTerm.parent != nil && currentTerm.parent.tk.Sym != SymSelector {
@@ -465,6 +469,7 @@ func (parser *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarR
 		}
 		// lastSym = tk.Sym
 	}
+
 	if err == nil {
 		err = tk.Error()
 	}
@@ -477,3 +482,49 @@ func (parser *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarR
 // 	}
 // 	return
 // }
+
+func (parser *parser) expandOpAssign(scanner * scanner, tree *ast, tk *Token, allowVarRef bool) (t *term, err error) {
+	var opSym Symbol
+	var opString string
+
+	if tree.root != nil {
+		switch tk.Sym {
+		case SymPlusEqual:
+			opString = "+"
+			opSym = SymPlus
+		case SymMinusEqual:
+			opString = "-"
+			opSym = SymMinus
+		case SymStarEqual:
+			opString = "*"
+			opSym = SymStar
+		default:
+			err = tk.Errorf("unsopported operator %q", tk.source)
+			return
+		}
+		leftExpr := tree.root.Clone()
+		leftExpr.setParent(nil)
+		if t, err = tree.addToken(NewToken(tk.row, tk.col, SymEqual, "=")); err == nil {
+			t = leftExpr
+			if err = tree.addTerm(leftExpr); err == nil {
+				if t, err = tree.addToken(NewToken(tk.row, tk.col, opSym, opString)); err == nil {
+
+					var subTree *ast
+					if subTree, err = parser.parseGeneral(scanner, false, allowVarRef, SymSemiColon, SymClosedRound, SymClosedBrace, SymClosedSquare); err == nil {
+						if scanner.Previous().IsOneOfA(SymSemiColon, SymClosedRound, SymClosedBrace, SymClosedSquare) {
+							if err = scanner.UnreadToken(); err != nil {
+								return
+							}
+						}
+						subTree.root.priority = priValue
+						err = tree.addTerm(newExprTerm(subTree.root))
+						t = subTree.root
+					}
+				}
+			}
+		}
+	} else {
+		err = tk.Errorf("left operand of %q must be a variable or a variable expression", tk)
+	}
+	return
+}

scanner.go

@@ -16,6 +16,7 @@ import (
 type scanner struct {
 	current      *Token
 	prev         *Token
+	stage        *Token
 	stream       *bufio.Reader
 	row          int
 	column       int
@@ -74,6 +75,16 @@ func (scanner *scanner) unreadChar() (err error) {
 	return
 }
 
+func (scanner *scanner) UnreadToken() (err error) {
+	if scanner.stage == nil {
+		scanner.stage = scanner.current
+		scanner.current = scanner.prev
+	} else {
+		err = fmt.Errorf("staging already present, currently one level only of staging is allowed")
+	}
+	return
+}
+
 func (scanner *scanner) lastPos() (r, c int) {
 	if scanner.prev != nil {
 		r = scanner.prev.row
@@ -89,7 +100,12 @@ func (scanner *scanner) Previous() *Token {
 func (scanner *scanner) Next() (tk *Token) {
 	scanner.prev = scanner.current
 	tk = scanner.current
+	if scanner.stage != nil {
+		scanner.current = scanner.stage
+		scanner.stage = nil
+	} else {
 		scanner.current = scanner.fetchNextToken()
+	}
 	return tk
 }
 
@@ -124,6 +140,8 @@ func (scanner *scanner) fetchNextToken() (tk *Token) {
 				tk = scanner.moveOn(SymDoubleStar, ch, next)
 				// } else if next == '/' {
 				// 	tk = self.moveOn(SymClosedComment, ch, next)
+			} else if next, _ = scanner.peek(); next == '=' {
+				tk = scanner.moveOn(SymStarEqual, ch, next)
 			} else {
 				tk = scanner.makeToken(SymStar, ch)
 			}

symbol.go

@@ -68,6 +68,7 @@ const (
 	SymDoubleDollar                      //  57: '$$'
 	SymDoubleDot                         //  58: '..'
 	SymTripleDot                         //  59: '...'
+	SymStarEqual                         //  60: '*='
 	SymChangeSign
 	SymUnchangeSign
 	SymIdentifier

t_ast_test.go

@@ -47,7 +47,7 @@ func TestAddUnknownTokens(t *testing.T) {
 	wantErr := errors.New(`unexpected token "%"`)
 
 	tree := NewAst()
-	if gotErr := tree.addToken(tk0); gotErr != nil && gotErr.Error() != wantErr.Error() {
+	if _, gotErr := tree.addToken(tk0); gotErr != nil && gotErr.Error() != wantErr.Error() {
 		t.Errorf("err: got <%v>, want <%v>", gotErr, wantErr)
 	}
 }

t_expr_test.go

@@ -17,7 +17,18 @@ func TestExpr(t *testing.T) {
 		/*   3 */ {`builtin "os.file"; f=fileOpen("test-file.txt"); line=fileReadText(f); fileClose(f); line`, "uno", nil},
 		/*   4 */ {`mynot=func(v){int(v)?{true}::{false}}; mynot(0)`, true, nil},
 		/*   5 */ {`1 ? {1} : [1+0] {3*(1+1)}`, int64(6), nil},
-		/*   6 */ {`
+		/*   6 */ {`a=3; a+=1`, int64(4), nil},
+		/*   7 */ {`a=3; a-=1`, int64(2), nil},
+		/*   8 */ {`a=3; a*=2`, int64(6), nil},
+		/*   9 */ {`v=[10,20,30]; v[0]+=1; v[0]`, int64(11), nil},
+		/*  10 */ {`r={"a":10}; r["a"]+=1; r["a"]`, int64(11), nil},
+		/*  11 */ {`a=3; a/=2`, nil, `[1:8] left operand of "=" must be a variable or a collection's item`},
+		/*  12 */ {`*=2`, nil, `[1:2] left operand of "*=" must be a variable or a variable expression`},
+		/*  13 */ {`a=3; a*=2+1; a`, int64(9), nil},
+		/*  14 */ {`a=3; (a*=2)+1; a`, int64(6), nil},
+		/*  15 */ {`a=3; a*=2)+1; a`, nil, `[1:11] unexpected token ")"`},
+		/*  16 */ {`v=[2]; a=1; v[a-=1]=5; v[0]`, int64(5), nil},
+		/*  17 */ {`
 		ds={
 			"init":func(@end){@current=0 but true},
 			//"current":func(){current},
@@ -32,6 +43,6 @@ func TestExpr(t *testing.T) {
 	}
 	// t.Setenv("EXPR_PATH", ".")
 
-	//runTestSuiteSpec(t, section, inputs, 6)
+	//runTestSuiteSpec(t, section, inputs, 9)
 	runTestSuite(t, section, inputs)
 }

term.go

@@ -53,6 +53,25 @@ type term struct {
 	evalFunc evalFuncType
 }
 
+func (s *term) Clone() (d *term) {
+	var children []*term
+	if s.children != nil {
+		children = make([]*term, len(s.children))
+		for i, c := range s.children {
+			children[i] = c.Clone()
+		}
+	}
+	d = &term{
+		tk: *s.tk.Clone(),
+		parent: s.parent,
+		children: children,
+		position: s.position,
+		priority: s.priority,
+		evalFunc: s.evalFunc,
+	}
+	return
+}
+
 func (term *term) String() string {
 	var sb strings.Builder
 	term.toString(&sb)

token.go

@@ -51,6 +51,10 @@ func NewErrorToken(row, col int, err error) *Token {
 	return NewValueToken(row, col, SymError, fmt.Sprintf("[%d:%d]", row, col), err)
 }
 
+func (tk *Token) Clone() (c *Token) {
+	return NewValueToken(tk.row, tk.col, tk.Sym, tk.source, tk.Value)
+}
+
 func (tk *Token) IsEos() bool {
 	return tk.Sym == SymEos
 }
@@ -67,6 +71,10 @@ func (tk *Token) IsOneOf(termSymbols []Symbol) bool {
 	return termSymbols != nil && slices.Index(termSymbols, tk.Sym) >= 0
 }
 
+func (tk *Token) IsOneOfA(termSymbols ...Symbol) bool {
+	return slices.Index(termSymbols, tk.Sym) >= 0
+}
+
 func (tk *Token) IsSymbol(sym Symbol) bool {
 	return tk.Sym == sym
 }