[Retros] Types B/C Last Move problems (using DR)

[andrew buchanan]

Dear Retrons,

I did some work a couple of weeks ago on Type B/C Last Move problems using
Dead Reckoning. Now is as good a time to publicize them as any. Type B = we
know whose move it is, but no-one is in check. Type C = we aren't told whose
move it is, but someone may be in check.

(1) En passant

Historically, en passant could not be solved as a Type B problem, because to
distinguish the double-step from the single-step requires a check in the
diagram. But now...

Original
4kBKN/3pPRRB/3PpPP1/4p3/4P3/5pP1/8/8 (12+5) White to move. Last move?
17/023

I don't think I can make a Type A e.p., even with DR.

(2) DR can help improve a very few other records. Here are the ones that
I've come up with, from looking through my files:

Type B BxN
6bk/8/6K1/3B4/8/8/8/8 (2+2) White to move. Last move? (my ref #030)
4/002 (older record: 7/021)

Type C BxN (two examples - pick one)
8/7k/8/8/8/8/8/KB6 (2+1) Last move? (my ref #006)
8/8/8/8/8/3k4/8/1B1K4 (2+1) Last move? (my ref #029)
3/001 (older record: 6/002)

Type B KxN
k7/8/1K6/7B/8/8/8/8 (2+1) White to move. Last move? (my ref #043) (wB could
be on any light square that doesn't attack or occupy a8 or c8.)
3/001 (older record: 4/001)

These last four have been on my website for a few years, so are in principle
already published (2001).

(3) What to do when the rules change?

I feel strongly that the three old pre-DR problems overtaken here should
remain on the site. A lot of work went into them, and in their time, they
were unbeaten. It's just the rules have changed.

On the other hand, the rules *have* changed slightly, which is fun and
interesting. I feel the new problems do deserve to appear alongside the old
ones, on an equal footing.

To me, this seems in keeping with the spirit of the Codex.

Independent of this issue, it would be nice to have the year of composition
shown for each of the problems posted in Retro Corner, to show how the ideas
have evolved, and also the periods during which various composers were
active.

Thanks & regards,
Andrew Buchanan.