From 99847d2bf132854fffa019bab19818768102ccad Mon Sep 17 00:00:00 2001
From: Howard Hinnant <hhinnant@apple.com>
Date: Sun, 27 Feb 2011 20:55:39 +0000
Subject: [PATCH] Fix copy_n to increment only n-1 times for an input iterator.
  This works much better with std::istream_iterator<int>(std::cin).  Credit:
 Matan Nassau.

llvm-svn: 126581
---
 libcxx/include/algorithm | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/libcxx/include/algorithm b/libcxx/include/algorithm
index d91c57c11098..4909221bb09f 100644
--- a/libcxx/include/algorithm
+++ b/libcxx/include/algorithm
@@ -1559,8 +1559,17 @@ typename enable_if
 >::type
 copy_n(_InputIterator __first, _Size __n, _OutputIterator __result)
 {
-    for (; __n > 0; --__n, ++__first, ++__result)
+    if (__n > 0)
+    {
         *__result = *__first;
+        ++__result;
+        for (--__n; __n > 0; --__n)
+        {
+            ++__first;
+            *__result = *__first;
+            ++__result;
+        }
+    }
     return __result;
 }