1 files changed, 9 insertions, 0 deletions
diff --git a/core/pair.h b/core/pair.h
index d75cbed642..174ffb3883 100644
--- a/core/pair.h
+++ b/core/pair.h
@@ -39,4 +39,13 @@ struct Pair {
 	Pair( F p_first,  S p_second) { first=p_first; second=p_second; }
 };
 
+template<class F,class S>
+struct PairSort {
+
+	bool operator()(const Pair<F,S>& A, const Pair<F,S>& B) const {
+		return A.first < B.first;
+	}
+};
+
+
 #endif // PAIR_H