anchor.diff:                                  {t, [{TimeD, minus({'#', TimeD}, 1)}]}}}},
                       {"X1",
                           {'if',
  -                            tand(
  -                                tand(gte({'#', XD}, 1), lte({'#', YD}, 1024)),
  -                                tand(gte({'#', YD}, 1), lte({'#', YD}, 1024))),
  -                            {'#', XD},
  +                            [{tand(tand(gte({'#', XD}, 1), lte({'#', YD}, 1024)),
  +                                   tand(gte({'#', YD}, 1), lte({'#', YD}, 1024))),
  +                              {'#', XD}}],
                               1}}
                   ]},
               [{TimeD,2}, {XD,0}, {YD,0}]},
  
positive.code:                 }
              },
              {"B", {'if',
                      tand(gte({'#', SpaceD}, 1),
                           lte({'#', SpaceD}, 1024)),
                      {'#', SpaceD},
                      1
                  }
              }
  
negative.code:         {wheredim,
              {wherevar, "A", [
              {"A", {'if',
                      [{lte({'#', TimeD}, 0), "B"}],
                      {'@',
                          plus({'@', "A", {t, [{SpaceD,      times({'#', SpaceD}, 2    )}]}},
                               {'@', "A", {t, [{SpaceD, plus(times({'#', SpaceD}, 2), 1)}]}}),
  