From a5bebbe77317d583dbf45909cc11f599c93c2065 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thorben=20Kr=C3=BCger?= <tkr@emlix.com>
Date: Mon, 21 Jul 2025 16:43:39 +0200
Subject: [PATCH] WhereSequence: improve iteration performance by caching value
 lookup in iterate() call

---
 src/vm/wren_core.wren     | 13 +++++++++++--
 src/vm/wren_core.wren.inc | 13 +++++++++++--
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/src/vm/wren_core.wren b/src/vm/wren_core.wren
index f073062c2..4d10c7526 100644
--- a/src/vm/wren_core.wren
+++ b/src/vm/wren_core.wren
@@ -169,16 +169,25 @@ class WhereSequence is Sequence {
   construct new(sequence, fn) {
     _sequence = sequence
     _fn = fn
+    _cache_val = null
+    _cache_iter = null
   }
 
   iterate(iterator) {
     while (iterator = _sequence.iterate(iterator)) {
-      if (_fn.call(_sequence.iteratorValue(iterator))) break
+      var val = _sequence.iteratorValue(iterator)
+      if (_fn.call(val)) {
+        _cache_val = val
+        _cache_iter = iterator
+        break
+      }
     }
     return iterator
   }
 
-  iteratorValue(iterator) { _sequence.iteratorValue(iterator) }
+  iteratorValue(iterator) {
+    if (iterator == _cache_iter) return _cache_val else return _sequence.iteratorValue(iterator)
+  }
 }
 
 class String is Sequence {
diff --git a/src/vm/wren_core.wren.inc b/src/vm/wren_core.wren.inc
index be296cdf7..c928fe929 100644
--- a/src/vm/wren_core.wren.inc
+++ b/src/vm/wren_core.wren.inc
@@ -171,16 +171,25 @@ static const char* coreModuleSource =
 "  construct new(sequence, fn) {\n"
 "    _sequence = sequence\n"
 "    _fn = fn\n"
+"    _cache_val = null\n"
+"    _cache_iter = null\n"
 "  }\n"
 "\n"
 "  iterate(iterator) {\n"
 "    while (iterator = _sequence.iterate(iterator)) {\n"
-"      if (_fn.call(_sequence.iteratorValue(iterator))) break\n"
+"      var val = _sequence.iteratorValue(iterator)\n"
+"      if (_fn.call(val)) {\n"
+"        _cache_val = val\n"
+"        _cache_iter = iterator\n"
+"        break\n"
+"      }\n"
 "    }\n"
 "    return iterator\n"
 "  }\n"
 "\n"
-"  iteratorValue(iterator) { _sequence.iteratorValue(iterator) }\n"
+"  iteratorValue(iterator) {\n"
+"    if (iterator == _cache_iter) return _cache_val else return _sequence.iteratorValue(iterator)\n"
+"  }\n"
 "}\n"
 "\n"
 "class String is Sequence {\n"