code: void altMerge(OptMapInfo other, Encoding enc) {
          /* if (! is_equal_mml(&to->mmd, &add->mmd)) return ; */
          if (value == 0) return;
          if (other.value == 0 || mmd.max < other.mmd.max) {
              clear();
              return;
          }
  
          mmd.altMerge(other.mmd);
  
          int val = 0;
          for (int i=0; i<Config.CHAR_TABLE_SIZE; i++) {
              if (other.map[i] != 0) map[i] = 1;
              if (map[i] != 0) val += positionValue(enc, i);
          }
  
          value = val;
          anchor.altMerge(other.anchor);
      }
docs: alt_merge_opt_map_info