The target for phase 5 is sort-of reached: e.p. capture finally works automatically. The implementation is a bit flaky, though, in the sense that XBetza would allow some very strange forms of e.p. capture, which would not be handled correctly at all. Such as e.p.-capturing Checkers, or e.p. capture with a sliding move, or riders that create e.p. rights for their capture on the squares they leap over... It is hard to imagine any CV would ever use those.

So for now e.p. rights are only created by lame leaps, which is good enough for the double (or triple) push of Pawns.; if rights-creation is specified on a lame rider, only the first leap would create the rights. The e.p. squares are accumulated in a loop over all the squares that the lame leap passes through, in the array eps. By default this variable would hold a scalar 0, though.

    if & << 1 14 #mode:                   // must create e.p. rights
      set eps ( );                        // array to accumulate e.p. squares
      set to where #cursqr #dx #dy;       // only for the first leap!
      set k #cursqr;
      do while != #to #k and onboard #k:
        set k where #k #hx #hy;
        push eps #k;
      loop;
    endif;

If the generated move matches the input move, the e.p. rights it creates are copied from eps to the global variable epsqrs, and the global ep is set to the destination square. So that the immediately following move can consult those to decide if it can perform. Thus at the end of case 1 of the GotMove routine (where the matching is confirmed) we put:

      set epsqrs #eps;   // remember e.p. squares
      set ep #destsqr;   // remember e.p. victim location

Another simplifying assumption is made on the e.p. capture itself. Namely that this would only be specified on the final leg of a move, and that this leg will always be a leap. The test for an e.p. capture then only has to be done in the section of NextLeg that handles the end-point of the leg:

  if match #to #epsqrs and & 4 #mode:       // 4 = e.p.-capable, and hits e.p square
    gosub GotMove #startsqr #to #ep 0 0 1;  // ASSUMES ALWAYS LAST LEG! (1 = implied)
  endif;

Note that this doesn't test whether the e.p. square is empty. The fact that rights for now can only be created by a lame leap already guarantees this. But even if we would start to support other ways of e.p.-rights creation, e.g. by a hop, the burden would be on the creating code to decide if the hopped piece makes a suitable e.p. square (which then would open the possibility for a double capture).

Anyway, e.p. capture on Pawns (or in fact any piece) with Betza D, A, G or H initial moves by a simple leap now works. Note the e.p. capture is generated with the implied argument to GotMove set, so that it will be treated as an implied side effect; the user will only have to enter the move of its own Pawn.