From 0748b305934399a3e33b29335729b6eed25a46da Mon Sep 17 00:00:00 2001
From: timofey <tim@ongoteam.yaconnect.com>
Date: Tue, 1 Aug 2023 20:07:59 +0000
Subject: [PATCH] simplify `EvalTree::next`

---
 src/func/instances/stackless.rs | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/src/func/instances/stackless.rs b/src/func/instances/stackless.rs
index 0badc89..5d257fd 100644
--- a/src/func/instances/stackless.rs
+++ b/src/func/instances/stackless.rs
@@ -48,18 +48,22 @@ enum EvalTree<'a> {
 type Oet<'a> = Option<EvalTree<'a>>;
 
 impl<'a> EvalTree<'a> {
+    fn _next_composite(self, other: Box<Self>) -> Self {
+        match self {
+            Self::Atom(f) => match f.next() {
+                Some(newleft) => Self::Composite(Box::new(newleft), other),
+                None => *other,
+            },
+            Self::Composite(etll, etlr) => {
+                Self::Composite(etll, Box::new(Self::Composite(etlr, other)))
+            }
+        }
+    }
+
     fn next(self) -> Oet<'a> {
         match self {
             Self::Atom(f) => f.next(),
-            Self::Composite(etl, etr) => match *etl {
-                Self::Atom(f) => match f.next() {
-                    Some(newleft) => Some(Self::Composite(Box::new(newleft), etr)),
-                    None => Some(*etr),
-                },
-                Self::Composite(etll, etlr) => {
-                    Some(Self::Composite(etll, Box::new(Self::Composite(etlr, etr))))
-                }
-            },
+            Self::Composite(etl, etr) => Some(etl._next_composite(etr)),
         }
     }
 }