Re: Re: Parsing Chess Algebra Notation

[cyocum]

I took your advice and tried it backwards. As you will notice, I did this in a step by step fashion. I am sure that there are much more effient ways to do this. Also, it does not yet support the edge cases that you are talking about (that includes promotion). I just wanted to layout a bit more code for general commments and improvments. Also, thanks for all the help. I really appreciate it!

use strict;
use warnings;

my $move = "Qe4++";

#reverse as per dragonchild's suggestion
my @parsed = reverse split //, $move;

print join('', @parsed) . "\n";

my $check;
my $row;
my $col;
my $piece;

#convert the letters into appropriate numbers
#there is probably a faster way to to this
my %col_convert = (a => 0,
          b => 1,
          c => 2,
          d => 3,
          e => 4,
          f => 5,
          g => 6,
          h => 7);

foreach my $elem (@parsed) {
    #check for, well, check
    if($elem eq '+') {
    #start the process to see if this is a checkmate
    my $nextElem = shift @parsed;
    print "nextElem $nextElem" . "\n";

    #if it is then print
    if($nextElem eq '+') {
        print "Checkmate\n";
        next;
    } else {
        #otherwise put it back on the stack for the next
        #iteration
        unshift @parsed, $nextElem;
    }

    #then print check in this instance
    print "Check\n";
    }elsif($elem =~ m/[1-8]/) {
    $row = $elem;
    print "Row: $row\n";
    }elsif($elem =~ /[a-h]/) {
    #convert to number
    $col = $col_convert{$elem};
    print "Col: $col\n";
    }elsif($elem =~ m/x/) {
    #this is a capture to that square
    print "Capture on $col $row\n";
    }elsif($elem =~ /[KQRNB]/) {
    $piece = $elem;
    print "Piece to move is $piece\n";
    } else {
    die "not a valid move\n";
    }
}

[dragonchild]

Why are you making it so complicated for yourself? All you want to do is build a string that corresponds to the move. This means that you're attempting to build a state representation by parsing another state representation, one character at a time. The following may or may not be complete, but it's a good start. (I didn't do castling, leaving that as an exercise for the reader. I'd probably special-case it.)
Read more... (2 kB)

And the test code ...

Read more... (2 kB)