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

simple-store.go

@@ -11,6 +11,7 @@ import (
 )
 
 type SimpleStore struct {
+	parent    ExprContext
 	varStore  map[string]any
 	funcStore map[string]ExprFunc
 }
@@ -26,6 +27,14 @@ func NewSimpleStore() *SimpleStore {
 func filterRefName(name string) bool  { return name[0] != '@' }
 func filterPrivName(name string) bool { return name[0] != '_' }
 
+func (ctx *SimpleStore) SetParent(parentCtx ExprContext) {
+	ctx.parent = parentCtx
+}
+
+func (ctx *SimpleStore) GetParent() ExprContext {
+	return ctx.parent
+}
+
 func (ctx *SimpleStore) Clone() ExprContext {
 	return &SimpleStore{
 		varStore:  CloneFilteredMap(ctx.varStore, filterRefName),