From a28cded46b46edf628ab904918b5e407c4c63e95 Mon Sep 17 00:00:00 2001
From: Solomon Foster <colomon@gmail.com>
Date: Wed, 29 Dec 2010 11:13:29 -0500
Subject: [PATCH] Allow a comparison function to be passed to sorted-merge.

---
 lib/List/Utils.pm   |  4 ++--
 t/06-sorted-merge.t | 20 ++++++++++++++++++++
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/lib/List/Utils.pm b/lib/List/Utils.pm
index 251aafb..3d35d40 100644
--- a/lib/List/Utils.pm
+++ b/lib/List/Utils.pm
@@ -120,7 +120,7 @@ sub upper-bound(@x, $key) is export(:DEFAULT) {
     return $first;
 }
 
-sub sorted-merge(@a, @b) is export(:DEFAULT) {
+sub sorted-merge(@a, @b, &by = &infix:<cmp>) is export(:DEFAULT) {
     my $a-list = @a.iterator.list;
     my $b-list = @b.iterator.list;
     
@@ -128,7 +128,7 @@ sub sorted-merge(@a, @b) is export(:DEFAULT) {
     my $b = $b-list.shift;
     gather loop {
         if $a.defined && $b.defined {
-            if $a before $b {
+            if &by($a, $b) == -1 {
                 my $temp = $a;
                 take $temp;
                 $a = $a-list.shift;
diff --git a/t/06-sorted-merge.t b/t/06-sorted-merge.t
index d3e0fff..b119203 100644
--- a/t/06-sorted-merge.t
+++ b/t/06-sorted-merge.t
@@ -36,5 +36,25 @@ plan *;
        "sorted-merge correct with infinite lazy lists, order swapped";
 }
 
+{
+    my @a := 1, 1, *+* ... *;
+    my @b := 3, 6 ... *;
+    is ~sorted-merge(@a, @b)[^10], ~(1, 1, 2, 3, 3, 5, 6, 8, 9, 12), 
+       "sorted-merge correct with infinite lazy lists";
+    is ~sorted-merge(@b, @a)[^10], ~(1, 1, 2, 3, 3, 5, 6, 8, 9, 12), 
+       "sorted-merge correct with infinite lazy lists, order swapped";
+}
+
+{
+    my @a := 1, * * -1/2 ... *;
+    my @b := 1, 1/3, 1/9 ... *;
+    is ~sorted-merge(@a, @b, -> $a, $b { $b.abs <=> $a.abs })[^7].perl, 
+       (1, 1, -1/2, 1/3, 1/4, -1/8, 1/9).perl, 
+       "sorted-merge correct with custom comparison";
+    is ~sorted-merge(@b, @a, -> $a, $b { $b.abs <=> $a.abs })[^7].perl, 
+       (1, 1, -1/2, 1/3, 1/4, -1/8, 1/9).perl, 
+       "sorted-merge correct with custom comparison, order swapped";
+}
+
 
 done_testing;
\ No newline at end of file