feat: new system

pkg/engine/normalorder/engine.go

@@ -13,19 +13,19 @@ func (e Engine) Get() (lambda.Expression, error) {
 	return e.expr, nil
 }
 
-func (e Engine) Set(l lambda.Expression) error {
+func (e *Engine) Set(l lambda.Expression) error {
 	e.expr = l
 	return nil
 }
 
-func (e Engine) Step(i int) bool {
-	var reduced bool
-
+func (e *Engine) Step(i int) bool {
 	for range i {
-		e.expr, reduced = ReduceOnce(e.expr)
+		next, reduced := ReduceOnce(e.expr)
 		if !reduced {
 			return false
 		}
+
+		e.expr = next
 	}
 
 	return true