Selector operator, multi-operand, added

operator-selector.go

@@ -0,0 +1,70 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-selector.go
+package expr
+
+//-------- export all term
+
+func newSelectorTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		class:    classOperator,
+		kind:     kindUnknown,
+		children: make([]*term, 0, 3),
+		position: posMultifix,
+		priority: priSelector,
+		evalFunc: evalSelector,
+	}
+}
+
+func isSelectorCase(ctx exprContext, exprValue, caseSel any, caseIndex int) (selectedValue any, err error) {
+	caseData, _ := caseSel.(*selectorCase)
+	if caseData.filterList == nil {
+		selectedValue, err = caseData.caseExpr.Eval(ctx, false)
+	} else {
+		filterList := caseData.filterList.children
+		if len(filterList) == 0 && exprValue == int64(caseIndex) {
+			selectedValue, err = caseData.caseExpr.Eval(ctx, false)
+		} else {
+			var caseValue any
+			for _, caseTerm := range filterList {
+				if caseValue, err = caseTerm.compute(ctx); err != nil || caseValue == exprValue {
+					selectedValue, err = caseData.caseExpr.Eval(ctx, false)
+					break
+				}
+			}
+		}
+	}
+	return
+}
+
+func evalSelector(ctx exprContext, self *term) (v any, err error) {
+	var exprValue any
+	// var caseList []*term
+
+	if err = self.checkOperands(); err != nil {
+		return
+	}
+	exprTerm := self.children[0]
+	if exprValue, err = exprTerm.compute(ctx); err != nil {
+		return
+	}
+
+	caseList := self.children[1:]
+	for i, caseTerm := range caseList {
+		caseSel := caseTerm.value()
+		if v, err = isSelectorCase(ctx, exprValue, caseSel, i); err != nil || v != nil {
+			break
+		}
+	}
+	if err == nil && v == nil {
+		err = exprTerm.tk.Errorf("no case catches the value (%v) of the selection expression", exprValue)
+	}
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymSelector, newSelectorTerm)
+}