On Thu, 14 Nov 2002 14:33:04 +1100, Ken Williams wrote:
>
>On Thursday, November 14, 2002, at 01:04 PM, Matthew O. Persico
>wrote:
>
>>On Thu, 14 Nov 2002 11:49:56 +1100, Ken Williams wrote:
>>>
>>>Incidentally, I'd just write these as
>>>
>>>local $_ = $o->{lines}[0];
>>
>>As explained, you usually use $_ as assigned by Perl in for, map
>>,grep. From these snippets, it seems like $_ is being assigned and
>>used because:
>>
>>1) being too lazy (bad lazy) to use a 'my' 2) misguidedly think
>>that
>>not using 'my' saves a significant number of cycles 3) being too
>>cute.
>
>Actually, in some of them it looks like it's so that $_ can be
>used as the implicit target of a regular expression. I do that
>sometimes, particularly when writing something like a string
>tokenizer, because it reduces clutter quite a bit:
>
>local $_ = shift();
>if ( /^foo/gc ) {
>....
>} elsif ( /^bar/gc ) {
>....
>} elsif ( /^baz/gc ) {
>....
>} elsif ( /^quux/gc ) {
>....
>}
TIMTOOTDI (and this is safer)...
SWITCH: for(shift) {
/^foo/gc && do {
...;
last SWITCH;
};
/^bar/gc && do {
...;
last SWITCH;
};
/^baz/gc && do {
...;
last SWITCH;
};
/^quux/gc && do {
...;
last SWITCH;
};
default:
## If we are here, nothing matched.
## Nothing special about the default: label
## in Perl, just an old K&R jockey at heart...
## And nothing special about the SWITCH label,
## either. I could have called it YO_MAMA:, but that
## is less self-documenting. :-)
}
In theory, as long as your tests are mutually exclusive, you do not
need the "last SWITCH;" statements. However, since you are doing shift(),
without the "last"s, you'll loop forever. Besides, it's safer to be
explicit.
--
Matthew O. Persico
