Add a function object to compare the first or second component of a std::pair.

Replace instances of this scattered around the code base.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189169 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 16 insertions, 0 deletions

diff --git a/include/llvm/ADT/STLExtras.h b/include/llvm/ADT/STLExtras.h
index dacda36521..bfe1392a67 100644
--- a/include/llvm/ADT/STLExtras.h
+++ b/include/llvm/ADT/STLExtras.h
@@ -217,6 +217,22 @@ inline tier<T1, T2> tie(T1& f, T2& s) {
   return tier<T1, T2>(f, s);
 }
 
+/// \brief Function object to check whether the first component of a std::pair
+/// compares less than the first component of another std::pair.
+struct less_first {
+  template <typename T> bool operator()(const T &lhs, const T &rhs) const {
+    return lhs.first < rhs.first;
+  }
+};
+
+/// \brief Function object to check whether the second component of a std::pair
+/// compares less than the second component of another std::pair.
+struct less_second {
+  template <typename T> bool operator()(const T &lhs, const T &rhs) const {
+    return lhs.second < rhs.second;
+  }
+};
+
 //===----------------------------------------------------------------------===//
 //     Extra additions for arrays
 //===----------------------------------------------------------------------===//