Path: csiph.com!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail
From: Arno Welzel <usenet@arnowelzel.de>
Newsgroups: comp.lang.javascript
Subject: Re: Logic conundrums in check
Date: Fri, 18 Sep 2020 12:53:36 +0200
Lines: 61
Message-ID: <hsjhtgF7jajU1@mid.individual.net>
References: <05dec20a-bc09-49d0-907d-b36b2387ea73o@googlegroups.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit
X-Trace: individual.net tn3n1D1xIjixElpLZOB1kgThCBK94anJYjzAyeuJFC0iU8hVB7
Cancel-Lock: sha1:uvWRA2/3doVly2aFhk2r/laA4rM=
In-Reply-To: <05dec20a-bc09-49d0-907d-b36b2387ea73o@googlegroups.com>
Content-Language: en-US
Xref: csiph.com comp.lang.javascript:38804

On 17.09.20 12:25, Jonas Thörnvall wrote:

> I am a bit baffeled about the complexity of checking for check. 
> Checking if the opponent make you check is straightforward, it is
> just to scan the "occupied/controled tiles" of the opponent piece
> just moved.
> 
> Similar to check if the king move into an opponent
> "occupied/controled" tile you just do two loops first scan thru kings
> possible "normal moves" and the other loop compare possible kingtiles
> with the opponents "occupied/controlled" tiles.
> 
> But knowing if you move one of your own pieces to cause your own king
> to be checked seem to be a complete different animal.

Why? You just execute the move and then check the result.

> First you have to find your kings position "tile" i don't keep track
> of it. Then it seem i actually have to make a "test move" actually

Why don't you keep track on which tile the king is?

> moving my own piece to a new position. And then do the above king vs
> opponenet controled tiles.
> 
> So to check if your king actually will become checked when you move a
> piece seem to be the most computing intensive part of rules?

No. This is just, because your data structures seem to lack information.
Every piece you move can have a current position and a future position
for a proposed move which is not done yet. So you can check with the
positions the current status and the status which might be if a move
will really be done.

> So all your own pieces and their possible moves multiplied by
> opponents all pieces and their possible moves compared with your king
> position, to see if King is checked?

No. You just need to check the current positions and the *single* piece
if you want to move it.

> Its clearly the most complex thing to program in chess so far.

Just because you did not break down the logic yet.

As I mentioned a while ago already - there is a complete(!) chess
implementation in JavaScript with less than 3 KB total:

<https://nanochess.org/chess4.html>

A working example:

<https://nanochess.org/archive/toledo_javascript_chess_3.html>

Yes - this is a bit brainfuck since the code is extremely optimized. But
it really works.


-- 
Arno Welzel
https://arnowelzel.de