adding clear, empty, at functions

extras/AssociativeContainers/map.hpp

@@ -25,4 +25,12 @@ class Map
     size_t size()                   { return this->map.size(); }
 
     V& operator[] (K const& key)    { return this->map[key]; }
+
+    V& at(K const& key)             { return this->map.at(key); }
+
+    bool empty() const noexcept     { return this->map.empty(); }
+
+    size_t max_size() const         { return this->map.max_size(); }
+
+    void clear() noexcept           { this->map.clear(); }
 };

source/stdcpp/map.d

@@ -30,4 +30,17 @@ module stdcpp.map;
     {
         return this.opIndex(key); // handle rvalue-ref
     }
+
+    ref Value at( ref const Key key);
+
+    ref Value at(const Key key)
+    {
+        return this.at(key);
+    }
+
+    bool empty() const nothrow;
+
+    size_t max_size() const;
+
+    void clear() nothrow;
  }

source/stdcpp/test/map.d

@@ -17,4 +17,9 @@ unittest
     mymap.opIndex(2) = 'b';
     mymap.opIndex(3) = 'c';
     assert(mymap.size == 3);
+    assert(mymap.empty == 0);
+    assert(mymap.at(2) == 'b');
+    mymap.clear();
+    assert(mymap.size == 0);
+    assert(mymap.empty == 1);
 }