 
     switch (format)
     {
-    case ASCII:
+    case ASCII_FORMAT:
         success = to_ascii( reads_name, output_file, output_index, qencoding, io::SequenceEncoding(encoding_flags) );
         break;
-    case PACKED2:
+    case PACKED2_FORMAT:
         success = to_packed<2u>( reads_name, output_file, output_index, qencoding, io::SequenceEncoding(encoding_flags) );
         break;
-    case PACKED4:
+    case PACKED4_FORMAT:
         success = to_packed<4u>( reads_name, output_file, output_index, qencoding, io::SequenceEncoding(encoding_flags) );
         break;
     }


enum Format
{
    ASCII   = 0u,
    PACKED2 = 1u,
    PACKED4 = 2u,
};

int main(int argc, char* argv[])

        else if (strcmp( argv[i], "-a" ) == 0 ||
                 strcmp( argv[i], "--ascii" ) == 0)  // ascii format
        {
            format = ASCII_FORMAT;
        }
        else if (strcmp( argv[i], "-p2" ) == 0 ||
                 strcmp( argv[i], "--packed-2" ) == 0)  // 2-bits packed
        {
            format = PACKED2_FORMAT;
        }
        else if (strcmp( argv[i], "-p4" ) == 0 ||
                 strcmp( argv[i], "--packed-4" ) == 0)  // 4-bits packed
        {
            format = PACKED4_FORMAT;
        }
        else if (strcmp( argv[i], "-i" ) == 0 ||
                 strcmp( argv[i], "--idx" ) == 0)       // index file
