From: Colin Paul Adams <colin <at> COLINA <dot> DEMON <dot> CO <dot> UK>
Date: 19 nov 1999
Subject: Re: Capturing a Chu Lion

>>>>> "Nick" == Nick Bardsley <nbardsley <at> ICC <dot> CO <dot> UK> writes:

    Colin> No. But it is illegal, because having first moved to an
    Colin> empty square, you can only then move back to the origin.

    Nick> Why so? I think it is one of these moves (common, it seems
    Nick> to me, in Shogi and its variants) that is legal (because it
    Nick> isn't defined as illegal) but simply would not be executed
    Nick> by any rational player.

Because the rules say so: (Lion rules (a) and (e) on page 6)

    Nick> Well, having read up properly (I hope). It seems clear that
    Nick> a pass move is a move to a (1) square and back to origin
    Nick> square and cannot, therefore, be executed if, for some
    Nick> reason, the Lion is unable to make the 1st part of the move
    Nick> to a (1) square. (I did read the stuff a bit back re passing
    Nick> moves being like a jump - it made no sense at all then, and
    Nick> now seems just ludicrous)

Quite right.

    Nick> I just don't see that this is controversial. Rule 4 clearly
    Nick> points out that there are restrictions when the enemy Lion
    Nick> is on a (2) square. It does not say that there are
    Nick> restrictions if the enemy Lion is on a (1) square: therefore
    Nick> there are no restrictions. Why would there be? The rules are
    Nick> intended to discourage and hamper early Lion exchanges, not
    Nick> make Lion exchanges nigh on impossible.

Rule 4 c) specifically says how you may capture a Lion on a (1)
square. That is Capture and move on (or back). This implies (to me)
that you cannot capture and not move the Lion. Of course, this is
nonsense, but there you are.

    Nick> PS. ;-) remember the 'hidden protector' in your program - I
    Nick> noticed last night (while setting up positions) that Steve
    Nick> Evans' ShogiVar doesn't take note of it and allows a Lion to
    Nick> capture an enemy Lion on a (2) square in the hidden
    Nick> protector case. (But then it also lets you capture a Lion on
    Nick> a (2) square by double-capture involving a pawn or a
    Nick> go-between...Sorry, Steve ;-] The program is still great.)

My program does all this correctly (I think), as also the repetition
rule, bare king rule (now I am finally clear on it - thanks George),
promotion rules, and even (optionally) touch-and-move! it is ready to
release now, but probably I won't do so until next weekend. It plays
with a 2-ply search, and no intelligence, in about two minutes on a
450MHz Pentium II, so fairly slow, and dreadfully weak (improvements
in later releases). This is a result of writing it in Java
(interpreted, so slow, but portable across nearly all operating systems).
--
Colin Paul Adams
Preston Lancashire