new operator '111123' that returns the content of the current context or the context of an iterator

operator-context.go

@@ -0,0 +1,49 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-context-value.go
+package expr
+
+//-------- context term
+
+func newContextTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 1),
+		position: posPrefix,
+		priority: priPrePost,
+		evalFunc: evalContextValue,
+	}
+}
+
+func evalContextValue(ctx ExprContext, self *term) (v any, err error) {
+	var childValue any
+
+	var sourceCtx ExprContext
+	if len(self.children) == 0 {
+		sourceCtx = ctx
+	} else if childValue, err = self.evalPrefix(ctx); err == nil {
+		if dc, ok := childValue.(*dataCursor); ok {
+			sourceCtx = dc.ctx
+		}
+	} else {
+		return
+	}
+
+	if sourceCtx != nil {
+		keys := sourceCtx.EnumVars(func(name string) bool { return name[0] != '_' })
+		d := make(map[string]any)
+		for _, key := range keys {
+			d[key], _ = sourceCtx.GetVar(key)
+		}
+		v = d
+	} else {
+		err = self.errIncompatibleType(childValue)
+	}
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymDoubleDollar, newContextTerm)
+}

scanner.go

@@ -242,6 +242,8 @@ func (self *scanner) fetchNextToken() (tk *Token) {
 			if next, _ := self.peek(); next == '(' {
 				tk = self.moveOn(SymDollarRound, ch, next)
 				tk.source += ")"
+			} else if next == '$' {
+				tk = self.moveOn(SymDoubleDollar, ch, next)
 			} else {
 				tk = self.makeToken(SymDollar, ch)
 			}

symbol.go

@@ -64,6 +64,7 @@ const (
 	SymCaret                             //  53: '^'
 	SymDollarRound                       //  54: '$('
 	SymOpenClosedRound                   //  55: '()'
+	SymDoubleDollar                      //  56: '$$
 	SymChangeSign
 	SymUnchangeSign
 	SymIdentifier