Ratings & Comments

Fergus,

I got stuck at the command that checks if the number of turns is larger than 8. How do I proerly write this?

My code uses:

if mln > 8 :
delete p2;
else:...

This is always true for some reason.

Commen t edit.

Moreover I cannot use setsytem starpath as it gives the error  You may not set $starpath(!p2 with setsystem.

Great idea. I have always loved Fischerrandom Chess, but I really don't like the way it gives players no control over where their pieces start. I also consider Fischer's castling rule to be cludgy and it's hard to believe that a man of his genius came up with that. Your project fixes those shortcomings. 

One tweak I'd make if it were up to me is to require both players to enter ALL their pieces before making any other moves. White would enter a piece, followed by black, and they'd take it in turns to enter pieces, one at a time, until the first and eighth ranks were full. Of course, Bishops must be required to be on different coloured squares. 

Operators must precede the operands in GAME Code. So the line " if mln > 8 " should be "if > mln 8" except that mln is not what you want to use here. This is not a measure of turns. It is the line number of a line in the movelist, and it can be affected by the presence of comments. What you want to use instead of mln is turn.

@Bruce:

I converted my 4-men EGT generator to doing the Omega Chess board. (I mapped the board into an 11x12, and then it effectively only needs 122 elements, as neighboring boards can be partly interleaved.)

Oddly enough this confirms the numbers you gave for Bishop+Knight and Wizard+Knight!

What I had not realized is that these end-games are not generally won at all, but are mosty fortress draws: you can only deliver mate in the corner of the Bishop's/Wizard's shade, as you need to cover both the corner and the Wizard square, or the King will simply escape to the latter. And if the bare King takes shelter in the other corner there is no way to smoke him out of the Wizard square there. So you have to go through excessive trouble to prevent the bare King fleeing into that corner, which apparently causes an enormous slowdown. On a normal board it is easy to drive the King along the edge from one corner to the other, so trying to reach whatever corner is not a good defensive strategy there.

As a consequence, only 38.3% of the KBNK positions are won (22.3% lost), and 33.7% of the KWNK positions (17.9% lost). Against 99.8%won / 81% lost on regular 10x10.

Your 3-men generator seems buggy, though; as the checkmating applet here shows, WD is a quite easy win on 8x8.

$starpath is an array of two arrays. This should do:

setsystem starpath ((!p2) (!p9));

You don't need to use the reserve command if you place the Jokers there in your FEN code.

What you should learn from Extra Move Chess is how to program your code to deal with two moves made by the same player on the same turn. While Chess allows Pawn Promotion as two moves without going through this, this is because adding a piece to a space does not change the values of $origin and $dest. However, dropping a piece does. It counts as a complete move just as much as moving a piece on the board.

The first line in Extra Move Chess's Post-Move section is

set mvs explode chr 59 thismove;

This line creates an array of all the moves made. It uses chr 59 to tell the explode function to split the string returned by thismove where semicolons appear.

The next line restores the position to what it was when it was stored in the Pre-Move section.

Some of the stuff that follows is peculiar to Extra Move Chess. The main thing to pay attention to is how it uses the elements of the mvs array to replay each individual move before testing its legality.

If you don't want to program the game as though it were a double move variant, then you could introduce the Joker to the board with an add move. This is the kind of move used in Pawn promotion. It uses the piece notation with a hyphen and a destination. Unlike a regular move, it does not include an origin space.

Why does it say stalemate is not possible? It seems the diagram of which it is claimed the best Valkyrie move is capturing the Forest Ox (Vf1xf7) actually leads directly into stalemate, through that move. After it black has no legal moves, and after hypothetical null move white cannot capture both his Kings at once, so he is not in check either. (And besides, the last black piece could have been taken elsewhere, so that neither black King would have been under attack.)

One of the things that can make programming double moves more difficult is the loss of information about the previous move. To help correct that, I have added three new variables called $prevmoved, $prevorigin and $prevdest. These store the previous values of $moved, $origin and $dest respectively. Using these, you could detect whether a Joker has been dropped and test whether the previous move was legal. Here's how it could work.

Instead of using $moved, $origin and $dest in the code for evaluating the main move, use some variables, such as #piece, #from and #to. If the last move was a Joker drop, set these variables to $prevmoved, $prevorigin, and $prevdest. Otherwise, set them to $moved, $origin, and $dest. Evaluate the move. Then if a Joker drop was made, evaluate that.

For entering the block of code that is about the joker insertion I try to use these commands. Why am I wrong? 

verify flag space $origin; 

verify == space p2 J;

Seems clear to me. A player with only kings is forced to pass. "Checkmate" is not a thing. You just take the kings.

Vxf7 pass Vxg7 pass Kd6;-e6 1-0