overload map at with a default parameter

alib2std/src/extensions/container/map.hpp

@@ -163,6 +163,24 @@ public:
 		return insert ( std::make_pair ( std::move ( key ), std::move ( value ) ) );
 	}
+	using std::map< T, R, Cmp, Alloc >::at;
+
+	R & at ( const T & key, R & defaultValue ) {
+		auto value = this->find ( key );
+		if ( value == end ( ) )
+			return defaultValue;
+		else
+			return value->second;
+	}
+
+	const R & at ( const T & key, const R & defaultValue ) const {
+		auto value = this->find ( key );
+		if ( value == end ( ) )
+			return defaultValue;
+		else
+			return value->second;
+	}
+
 	/**
 	 * \brief
 	 * Inherited behavior of begin for non-const instance.

alib2std/test-src/extensions/container/MapTest.cpp

@@ -55,4 +55,23 @@ TEST_CASE ( "Map", "[unit][std][container]" ) {
 		CHECK ( copies == 0 );
 	}
+
+	SECTION ( "At" ) {
+		ext::map < int, std::string > map;
+		map.insert ( 1, "one" );
+
+		{
+			std::string defaultValue = "default";
+			std::string & value = map.at ( 0, defaultValue );
+
+			CHECK ( value == "default" );
+		}
+
+		{
+			const std::string defaultValue = "default";
+			const std::string & value = map.at ( 0, defaultValue );
+
+			CHECK ( value == "default" );
+		}
+	}
 }