From a7e4524470d9ff37288d111a0b118e56d0fee069 Mon Sep 17 00:00:00 2001
From: Pekka Laiho <pekka.i.laiho@gmail.com>
Date: Sat, 17 Oct 2020 13:32:57 +0700
Subject: [PATCH] add usort

---
 README.md               | 1 +
 src/Lib/Collections.php | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/README.md b/README.md
index 0e6d2a4..b071bee 100644
--- a/README.md
+++ b/README.md
@@ -179,6 +179,7 @@ keys    | `(keys {"a" 1 "b" 2})` | `("a" "b")` | Return a list of the keys for a
 values  | `(values {"a" 1 "b" 2})` | `(1 2)` | Return a list of the values for a hash-map.
 zip     | `(zip ["a" "b"] [1 2])` | `{"a":1 "b":2}` | Create a hash-map using the first sequence as keys and the second as values. Uses [array_combine](https://www.php.net/manual/en/function.array-combine.php) internally.
 sort    | `(sort [6 4 8 1])` | `[1 4 6 8]` | Sort the sequence using [sort](https://www.php.net/manual/en/function.sort.php).
+usort   | `(usort (fn (a b) (if (< a b) 0 1)) [3 1 5 4 2])` | `[1 2 3 4 5]` | Sort the sequence using custom comparison function using [usort](https://www.php.net/manual/en/function.usort.php).
 
 ### Comparison functions
 
diff --git a/src/Lib/Collections.php b/src/Lib/Collections.php
index 48548b1..aa7632e 100644
--- a/src/Lib/Collections.php
+++ b/src/Lib/Collections.php
@@ -240,5 +240,13 @@ class Collections implements ILib
                 return $a::new($data);
             }
         ));
+
+        $env->set('usort', new CoreFunc('usort', 'Sort the sequence using custom comparison function.', 2, 2,
+            function (Func $f, Seq $a) {
+                $data = $a->getData();
+                usort($data, $f->getClosure());
+                return $a::new($data);
+            }
+        ));
     }
 }