Comments/Ratings for a Single Item

This guide now describes the following new commands:

setflag, unsetflag, copyflag

add, move, replace

if, else, elseif, endif, verify

The verify command was already available, but it has now been greatly
expanded.

I created some of these commands for use with Crazyhouse, and I created
others because of their similarity to other commands I was creating. In
particular, the new Crazyhouse preset tracks Pawns with flags, uses verify
to check the flag of a captured piece, then uses add to change it to a
Pawn if it used to be one. Although I didn't use them, I also figured out
how to implement nesting if, if-else, and if-elseif-else statements. I
haven't thoroughly tested them out yet, but I expect they should work.

Is it possible to create a 'Stratego'-like game with the following
characteristics?

- each player can see his own pieces but not his opponents
- players are able to choose the placement of their pieces before starting

Is it possible to create a 'Stratego'-like game with the following
characteristics?

- each player can see his own pieces but not his opponents
- players are able to choose the placement of their pieces before starting

In preparation for a British Chess preset, I have added some new features
to Game Courier that are now documented here. These are the path function
and the foreach-next loop. The path function returns an array of all steps
from one space to another. The foreach-next loop iterates through all the
elements of an array. Although I could do it, I don't plan to add
additional types of looping, since I don't want to provide the ability to
create infinite loops. Foreach should be sufficient for any looping needs
any preset has.

Also, I am deprecating how endif currently works. In the future, endif
will automatically close off all elseifs within the scope of the current
if, which it will also close. There will no longer be any need to use
numbers or the all keyword with endif. I could make the switch right away
if everyone wrote endifs the same way I do, but just in case anyone has
used endif arguments for shortcuts that close off multiple ifs, not just
multiple elseifs and a single if, I am allowing time for transition before
the old way of using endif breaks down. To make the transition, replace any
use of 'endif all' or 'endif #' with 'endifs' and make sure that each
'endifs' statement closes off only one 'if' statement. The 'endifs'
command works in the same way that 'endif' eventually will.

I've changed how next works since last night. It no longer uses any
arguments. It just updates whatever loop it is for and loops back if it
hasn't reached the end of the array yet.

I have added the for command. It works much the same as the foreach
command, but it uses a different syntax, and it uses an array expression
instead of an array name. If you had in mind something like 'for x = 1 to
8', you would write it as 'for x range 1 8'.

I have added the sub, return, and gosub commands for using subroutines.
The sub and return commands mark the beginning and end of a subroutine.
The gosub command goes to a subroutine. To prevent the possibility of
infinite loops, the gosub command cannot be used from within a subroutine.

I have written a comprehensive postauto1 and postauto2 code (with perhaps a
few bugs) which covers the 16 possibilities for Chess With Different
Armies. (All there is to change in each preset is the title in 'game',
the initial setup in 'code' and two arrays for possible promotions in
'pregame'.) Would it be possible to refer to a common postauto1 entry and
a common postauto2 entry, instead of having to maintain 16 identical
postauto1 entries and 16 identical postauto2 entries?
It would also be useful when there are several presets for a same game.

After creating user defined functions, I discovered that my Polish Notation
calculator wouldn't let recursive functions work. So I came up with some
replacements for cond, called unless and onlyif. These work sort of like
cond but with only two arguments instead of three. The expression 'cond x
y z' is supposed to be equivalent to 'x ? y : z' but it evaluates both y
and z, making it unsuitable for recursion. It ends up creating an infinite
loop when used for recursion. Unlike previous functions in the PNC, unless
and onlyif can break out of it, allowing recursion loops to be exited. I
won't describe them in detail here, because I already did in the
documentation.

After creating these new functions, I realized the same principle could be
applied to logical operators. So I updated and, or, nand, and nor to use
either one or two arguments. When only one argument is available, these
operators will stop evaluation of the expression when the truth value of
the whole expression can be known from one value. For example, I can now
write code like this:

def Q checkride origin dest 1 1 or checkride origin dest 1 0;

This function would evaluate the Rook moves before the Bishop moves, and
if the Queen moved like a Rook, it would return true without bothering to
check whether it moved like a Bishop.

So, finally, logical operators can be used for flow control in
expressions. They can also be used for exiting from recursive functions.

I've now brought together the new features I've been developing to write
a new Chess preset in a new way. Most of the code is in an include file
and can be viewed here:

http://play.chessvariants.org/pbm/includes/chess.txt

The code makes use of user-defined functions and subroutines. I am
currently using this new preset for the Chess preset with Abstract pieces.
I will begin using it for the others after I have tested it more
thoroughly.

I've debugged the code in the include file for Chess, and I've also made
it more generalized. I've included a castle subroutine that can make
castling much easier to implement, and I've generated arrays of which
pieces a Pawn may promote to out of the array of piece keys, which is
generated from the FEN code. I am now using this new version of the Chess
enforcement code for the Alfaerie JPG Chess preset as well as for the
Abstract Table preset.

http://play.chessvariants.org/pbm/includes/chess.txt

With the improvements I've recently made to GAME Code, it may now have
the computing power to spot checkmate, but it will still take someone to
figure out how to do it. I have a general of how to go about it. First,
check if the King is in check. If it is, then loop through the King's
possible moves, checking if any are legal. If none are legal, identify the
checking pieces. If there is more than one checking piece, it is checkmate.
Otherwise, check if any piece can legally capture the checking piece. If it
can't be captured, check if any piece can legally move to block the check.