From 75b33a7f64d2f04efeeb09f96e9b6be716a65526 Mon Sep 17 00:00:00 2001
From: Timo Weingärtner <timo@tiwe.de>
Date: Sun, 17 Nov 2013 14:23:02 +0100
Subject: tighten type requirements for range adaptors

---
 hadori.C | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/hadori.C b/hadori.C
index a96f1d6..f4f8e46 100644
--- a/hadori.C
+++ b/hadori.C
@@ -40,11 +40,13 @@ namespace po = boost::program_options;
 
 // needed for equal_range and range-for
 namespace std {
-template<typename T> T& begin(pair<T,T> & ip) {
-	return ip.first;
+template<typename It>
+typename enable_if<is_base_of<input_iterator_tag, typename iterator_traits<It>::iterator_category>::value, It&>::type begin(pair<It,It> & p) {
+	return p.first;
 }
-template<typename T> T& end(pair<T,T> & ip) {
-	return ip.second;
+template<typename It>
+typename enable_if<is_base_of<input_iterator_tag, typename iterator_traits<It>::iterator_category>::value, It&>::type end(pair<It,It> & p) {
+	return p.second;
 }
 }
 
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