ファイルなしでも開ける様に＋:oコマンドの追加

main.cc

@@ -39,13 +39,13 @@ OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 #include "src/hexeditor.hh"
 
 int main(int argc, char *argv[]) {
-  if (argc != 2) {
-    std::cerr << "usage: hexagon <filename>\n";
-    return 1;
-  }
+  std:: string filename;
+
+  if (argc > 1) filename = argv[1];
+  else filename = "";
 
   try {
-    HexEditor editor(argv[1]);
+    HexEditor editor(filename);
     editor.run();
   } catch (const std::exception &e) {
     std::cerr << "エラー： " << e.what() << "\n";