From c4dfaed19c278806ef395def1120b66992b3e33e Mon Sep 17 00:00:00 2001
From: Michel Hermier <michel.hermier@gmail.com>
Date: Mon, 28 Dec 2020 13:00:06 +0100
Subject: [PATCH] wren/core: Add `Sequence::find`.

---
 doc/site/modules/core/sequence.markdown |  7 +++++++
 src/vm/wren_core.wren                   | 10 ++++++++++
 src/vm/wren_core.wren.inc               | 10 ++++++++++
 test/core/sequence/find.wren            |  8 ++++++++
 4 files changed, 35 insertions(+)
 create mode 100644 test/core/sequence/find.wren

diff --git a/doc/site/modules/core/sequence.markdown b/doc/site/modules/core/sequence.markdown
index 94ee5d93d..f378f9f5d 100644
--- a/doc/site/modules/core/sequence.markdown
+++ b/doc/site/modules/core/sequence.markdown
@@ -66,6 +66,13 @@ Iterates over the sequence, passing each element to the given `function`.
 ["one", "two", "three"].each {|word| System.print(word) }
 </pre>
 
+### **find**(predicate), **find**(it, predicate)
+
+Returns an iterator on the sequence that pass the function `predicate`,
+starting from the begining of the sequence or `it` if provided.
+
+It is a runtime error if `it` is not a valid iterator value on the sequence.
+
 ### **isEmpty**
 
 Returns whether the sequence contains any elements.
diff --git a/src/vm/wren_core.wren b/src/vm/wren_core.wren
index 58033e7cc..9b684c622 100644
--- a/src/vm/wren_core.wren
+++ b/src/vm/wren_core.wren
@@ -52,6 +52,16 @@ class Sequence {
     }
   }
 
+  find(predicate) { find(iterate(null), predicate) }
+
+  find(it, predicate) {
+    while(it) {
+      if (predicate.call(iteratorValue(it))) break
+      it = iterate(it)
+    }
+    return it
+  }
+
   isEmpty { iterate(null) ? false : true }
 
   map(transformation) { MapSequence.new(this, transformation) }
diff --git a/src/vm/wren_core.wren.inc b/src/vm/wren_core.wren.inc
index 4b706f428..ec753c2a9 100644
--- a/src/vm/wren_core.wren.inc
+++ b/src/vm/wren_core.wren.inc
@@ -54,6 +54,16 @@ static const char* coreModuleSource =
 "    }\n"
 "  }\n"
 "\n"
+"  find(predicate) { find(iterate(null), predicate) }\n"
+"\n"
+"  find(it, predicate) {\n"
+"    while(it) {\n"
+"      if (predicate.call(iteratorValue(it))) break\n"
+"      it = iterate(it)\n"
+"    }\n"
+"    return it\n"
+"  }\n"
+"\n"
 "  isEmpty { iterate(null) ? false : true }\n"
 "\n"
 "  map(transformation) { MapSequence.new(this, transformation) }\n"
diff --git a/test/core/sequence/find.wren b/test/core/sequence/find.wren
new file mode 100644
index 000000000..aea40d11d
--- /dev/null
+++ b/test/core/sequence/find.wren
@@ -0,0 +1,8 @@
+
+var data = 0...100
+
+System.print(data.find {|value| value == -1 }) // expect: false
+System.print(data.iteratorValue(data.find {|value| value == 42 })) // expect: 42
+System.print(data.find {|value| value == 100 }) // expect: false
+
+System.print(data.iteratorValue(data.find(data.find {|value| value == 42 }) {|value| value %15 == 0})) // expect: 45