diff --git a/ast.go b/ast.go
index 8aadfd4..704ab0b 100644
--- a/ast.go
+++ b/ast.go
@@ -124,38 +124,3 @@ func (self *ast) Eval(ctx exprContext, preset bool) (result any, err error) {
 	}
 	return
 }
-
-// Preset variables
-const (
-	preset_last_result   = "_last"
-	preset_bool_shortcut = "_bool_shortcut"
-)
-
-func initDefaultVars(ctx exprContext) {
-	ctx.SetValue(preset_bool_shortcut, true)
-}
-
-func enable(ctx exprContext, name string) {
-	if strings.HasPrefix(name, "_") {
-		ctx.SetValue(name, true)
-	} else {
-		ctx.SetValue("_"+name, true)
-	}
-}
-
-func disable(ctx exprContext, name string) {
-	if strings.HasPrefix(name, "_") {
-		ctx.SetValue(name, false)
-	} else {
-		ctx.SetValue("_"+name, false)
-	}
-}
-
-func isEnabled(ctx exprContext, name string) (status bool) {
-	if v, exists := ctx.GetValue(name); exists {
-		if b, ok := v.(bool); ok {
-			status = b
-		}
-	}
-	return
-}