-/** Function object for insertion into third argument of STL's sort() etc. */
-class expair_is_less
-{
-public:
- bool operator()(const expair &lh, const expair &rh) const
- {
- return lh.is_less(rh);
- }
+/** Function objects for insertion into third argument of STL's sort() etc. */
+struct expair_is_less : public std::binary_function<expair, expair, bool> {
+ bool operator()(const expair &lh, const expair &rh) const { return lh.is_less(rh); }
+};
+
+struct expair_swap : public std::binary_function<expair, expair, void> {
+ void operator()(expair &lh, expair &rh) const { lh.swap(rh); }