operator-builtin.go: builtin "" output the list of builtin module names

operator-builtin.go

@@ -10,6 +10,7 @@ import (
 	"git.portale-stac.it/go-pkg/expr/kern"
 	"git.portale-stac.it/go-pkg/expr/scan"
 	"git.portale-stac.it/go-pkg/expr/sym"
+	"git.portale-stac.it/go-pkg/expr/types/list"
 	"git.portale-stac.it/go-pkg/expr/types/str"
 )
 
@@ -35,7 +36,17 @@ func evalBuiltin(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
 	count := 0
 	if str.IsString(childValue) {
 		module, _ := childValue.(string)
-		count, err = ImportInContextByGlobPattern(ctx, module)
+		if module == "" {
+			ll := list.NewLinkedList()
+			IterateBuiltinModules(func(name, description string, imported bool) bool {
+				ll.PushBack(name)
+				return true
+			})
+			v = ll
+			return
+		} else {
+			count, err = ImportInContextByGlobPattern(ctx, module)
+		}
 	} else {
 		var moduleSpec any
 		var it kern.Iterator