IsOptional() function of ExprFuncParam renamed as IdDefault(). A new IsOptional() function created to check if a param is optional without requiring a default value

operand-func.go

@@ -30,7 +30,7 @@ func checkFunctionCall(ctx ExprContext, name string, varParams *[]any) (err erro
 		}
 		for i, p := range info.Params() {
 			if i >= passedCount {
-				if !p.IsOptional() {
+				if !p.IsDefault() {
 					break
 				}
 				*varParams = append(*varParams, p.DefaultValue())
@@ -50,6 +50,7 @@ func checkFunctionCall(ctx ExprContext, name string, varParams *[]any) (err erro
 
 func evalFuncCall(parentCtx ExprContext, self *term) (v any, err error) {
 	ctx := cloneContext(parentCtx)
+	ctx.SetParent(parentCtx)
 	name, _ := self.tk.Value.(string)
 	params := make([]any, len(self.children), len(self.children)+5)
 	for i, tree := range self.children {
@@ -91,7 +92,7 @@ func evalFuncDef(ctx ExprContext, self *term) (v any, err error) {
 			var defValue any
 			flags := paramFlags(0)
 			if len(param.children) > 0 {
-				flags |= PfOptional
+				flags |= PfDefault
 				if defValue, err = param.children[0].compute(ctx); err != nil {
 					return
 				}