use std::function instead of std::binary_function (#102)

* use std::function instead of std::binary_function

* Add pair_1st_cmp struct for C++11 compatibility

* Fix pair_1st_cmp struct inheritance

* fix builds on Visual Studio 2022

* Add <functional> header

* Fix compatibility issue with Visual Studio 2022

mecab/src/dictionary.cpp

@@ -5,6 +5,7 @@
 //  Copyright(C) 2004-2006 Nippon Telegraph and Telephone Corporation
 #include <fstream>
 #include <climits>
+#include <functional>
 #include "connector.h"
 #include "context_id.h"
 #include "char_property.h"
@@ -64,13 +65,29 @@ int progress_bar_darts(size_t current, size_t total) {
   return progress_bar("emitting double-array", current, total);
 }
 
+#if defined(__cplusplus) && __cplusplus >= 201103L
+#  define HAS_STD_FUNCTION 1
+#else
+#  define HAS_STD_FUNCTION 0
+#endif
+
+#if HAS_STD_FUNCTION
+template <typename T1, typename T2>
+struct pair_1st_cmp: public std::function<bool(T1, T2)> {
+  bool operator()(const std::pair<T1, T2> &x1,
+                  const std::pair<T1, T2> &x2)  {
+    return x1.first < x2.first;
+  }
+};
+#else
 template <typename T1, typename T2>
 struct pair_1st_cmp: public std::binary_function<bool, T1, T2> {
   bool operator()(const std::pair<T1, T2> &x1,
                   const std::pair<T1, T2> &x2)  {
     return x1.first < x2.first;
   }
 };
+#endif
 }  // namespace
 
 bool Dictionary::open(const char *file, const char *mode) {