From 4a0637462e996807d834022a0e2cbe368c28a676 Mon Sep 17 00:00:00 2001
From: tsnorri <tsnorri@iki.fi>
Date: Mon, 28 May 2018 23:30:40 +0300
Subject: [PATCH 1/3] Add unfold

---
 LambdaExtension.php | 22 +++++++++++++++++++++-
 README.md           | 16 ++++++++++++++++
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/LambdaExtension.php b/LambdaExtension.php
index a62b05f..2454703 100644
--- a/LambdaExtension.php
+++ b/LambdaExtension.php
@@ -67,6 +67,7 @@ public function getFilters()
             new \Twig_SimpleFilter('group_by', '\DPolac\TwigLambda\LambdaExtension::groupBy'),
             new \Twig_SimpleFilter('sort_by', '\DPolac\TwigLambda\LambdaExtension::sortBy'),
             new \Twig_SimpleFilter('count_by', '\DPolac\TwigLambda\LambdaExtension::countBy'),
+            new \Twig_SimpleFilter('unfold', '\DPolac\TwigLambda\LambdaExtension::unfold'),
         ];
     }
     
@@ -292,9 +293,28 @@ public static function call($callback, array $args = [])
         }
         return call_user_func_array($callback, $args);
     }
+    
+    public static function unfold($state, $callback, array $unfolded = [])
+    {
+        if (!is_callable($callback)) {
+            throw new \InvalidArgumentException('First argument must be callable.');
+        }
+        
+        while (true)
+        {
+            $retval = $callback($state);
+            if (is_null($retval))
+                break;
+            
+            list ($newVal, $state) = $retval;
+            $unfolded[] = $newVal;
+        }
+        
+        return $unfolded;
+    }
 
     public function getName()
     {
         return 'dpolac_lambda_extension';
     }
-}
\ No newline at end of file
+}
diff --git a/README.md b/README.md
index 618c537..68c9e94 100644
--- a/README.md
+++ b/README.md
@@ -121,6 +121,22 @@ Returns array of elements that passes a test specified by lambda.
 
 ----------------------------------------------------------------
 
+<a name="unfold"></a>
+### |unfold
+**Signature:** `state|unfold(lambda[, retval = []])`
+
+Given a lambda that returns an array `[state, value]` or `null`, repeatedly
+calls the function until it returns `null` passing the new `state` on each
+call. Returns an array of the accumulated values.
+
+
+```twig
+{% do [1, 1]|unfold(=> _[1] > 1000 ? null : [ _[0] + _[1], [ _[1], _[0] + _[1]]], [1, 1]) %}
+{# Calculates the Fibonacci numbers up to and including 1597. #}
+```
+
+----------------------------------------------------------------
+
 <a name="unique_by"></a>
 ### |unique_by
 **Signature:** `array|unique_by(lambda|'==='|'==')`

From 2a4ad804ce27f49add601313dd8914217293327d Mon Sep 17 00:00:00 2001
From: Tuukka Norri <tsnorri@iki.fi>
Date: Tue, 29 May 2018 01:26:07 +0300
Subject: [PATCH 2/3] Fix argument order for unfold

---
 README.md | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index 68c9e94..48f7fb9 100644
--- a/README.md
+++ b/README.md
@@ -125,8 +125,8 @@ Returns array of elements that passes a test specified by lambda.
 ### |unfold
 **Signature:** `state|unfold(lambda[, retval = []])`
 
-Given a lambda that returns an array `[state, value]` or `null`, repeatedly
-calls the function until it returns `null` passing the new `state` on each
+Given a lambda that returns an array `[value, state]` or `null`, repeatedly
+calls the function until it returns `null`, passing the new `state` on each
 call. Returns an array of the accumulated values.
 
 

From 95fc5ae1e8392ec26e9ce708287848e24636cdc7 Mon Sep 17 00:00:00 2001
From: Justin Cherniak <justin@pinfirestudios.com>
Date: Wed, 12 Jun 2019 23:25:49 -0700
Subject: [PATCH 3/3] Fix #11 - Change operator to ==> to not conflict with
 built in => operator in Twig 2.10

---
 LambdaExtension.php | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/LambdaExtension.php b/LambdaExtension.php
index a62b05f..deb440e 100644
--- a/LambdaExtension.php
+++ b/LambdaExtension.php
@@ -19,13 +19,13 @@ public function getOperators()
     {
         return [
             [
-                '=>' => [
+                '==>' => [
                     'precedence' => 0,
                     'class' => '\DPolac\TwigLambda\NodeExpression\SimpleLambda'
                 ],
             ],
             [
-                '=>' => [
+                '==>' => [
                     'precedence' => 0,
                     'class' => '\DPolac\TwigLambda\NodeExpression\LambdaWithArguments',
                     'associativity' => \Twig_ExpressionParser::OPERATOR_LEFT
@@ -297,4 +297,4 @@ public function getName()
     {
         return 'dpolac_lambda_extension';
     }
-}
\ No newline at end of file
+}