note
gmax
<p>As a significant example of why flags can be messy, check this particularly thorny
<a href="http://search.cpan.org/src/MAIRE/Chess-Pgn-0.03/Pgn.pm">source code</a>.</p>
<p>I needed to use that <a href="http://search.cpan.org/perldoc?Chess::Pgn">module</a> and I found out that it was faulty. I tried to fix it, but its logic eluded me. I contacted the author, who didn't do anything, and therefore I wrote my own [id://141468|parser] using a rather different approach.</p>
<p>This module is supposed to parse chess games. The problem in this code is that it skips the last game in each file it parses. I was able to spot where the problem is. As for fixing it using the same labyrinth of flags system, I simply couldn't.</p>
<code>
##
## WARNING! broken code ahead!
##
my $FLAG=1;
my $GAME=0;
##
## ... snip
##
sub ReadGame
{
my $self=shift;
my $continue=1;
$self->_init();
do
{
if ( $continue == 2 ) { $continue = 0 }
if ( $LINE =~/\[(.*)\]/ )
{
my $line=$1;
my ($key,$val,$junk)=split(/"/,$line);
$key=~s/ $//g,
$self->{$key}=$val;
$GAME=0;
}
elsif ( $LINE !~/^$/)
{
$self->{Game}.=$LINE;
$GAME=1;
}
elsif ( $GAME == 1 )
{
$FLAG=0;
}
$LINE=<FICPGN>;
if ( eof(FICPGN) && $continue == 1 ) { $continue = 2 }
$LINE=~s/\r//;
}
while ( $FLAG==1 );
return ( $continue ) ;
}
</code>
This code uses not one but THREE flags, transforming a would-be OOP module into a peculiar example of spaghetti code.<br>
<CODE>
_ _ _ _
(_|| | |(_|><
_|
</CODE>
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