OOOOOOhhhhh, this has pissed me off.
Look at this piece of code. it says that if the substitution succeeds,
return a token. If it fails return undef and warn me.
sub eatOptionalArgument {
my $in = $_[0];
if ($in =~ s/^\s*$optionalArgument//) {
return new Token $1, $&;
} else {
warn "No optional argument found";
return undef;
}
}
Great. What could be nicer?
Hold on. Here's the RE in question. I direct your attention to the comment.
# matches either nothing OR an argument in brackets ($1 doesn't include [])
$optionalArgument = "(?:\\[([^]]*)\\])?"; # Contains one level of grouping
So. The bloody thing is always successful, whether a change took place or
not. It is impossible for that warning to be triggered. It exists simply to
sucker a mug like me who has just spent far too long scratching his head
over it.
Functionally identical, less offensive:
sub eatOptionalArgument {
my $in = $_[0];
my $token=undef;
# Note that this particular RE always succeeds in matching
# $in, so $token is always initialised.
if ($in =~ s/^\s*$optionalArgument//) {
$token = new Token $1, $&;
}
return $token;
}
Fade out stage left with howls of rage and gnashing of teeth.
--
Angus
