On Thu, Feb 3, 2011 at 4:59 PM, Harry Putnam <rea...@newsguy.com> wrote:
> May I ask how that formulation servers the purpose better? Is it
> processed more easily or quicker in that formulation as against the
> one I posted?
>
> Or does mine leave too many possibilities for poor results?
Yours just wasn't very precise:
> if ( !/^.*\.[bjgtp][gimnps][gfadp]$/) {
Instead of specifying valid extensions, you're specifying valid
first-characters, valid second-characters, and valid third-characters
for the file extension. Pick any random character from each bracket
expression (i.e., '[expression]') and you can generate file names that
would match and shouldn't. For example:
foo.jga
bar.ppp
baz.gma
Obviously not what you intended to match, but they will match
(untested). Using a full literal string for the extension means that
it needs to match the whole thing exactly. The alternation character
(i.e., '|') allows you to specify one of many valid options to choose
from. I find it rather luxurious. I know that other regular expression
engines seem to only permit first|second whereas Perl seems to allow
"any number"[1] of choices, which provides a lot more powerful
expressiveness.
In addition to the stricter matching rules, it's also rather more easy
to read, IMHO. Looking at my regular expression, it should be obvious
to any programmer and many computer users that it's matching image
file extensions. Yours appears much more random to a human. It might
suggest that it's matching file extensions, but it certainly doesn't
communicate well which ones it is supposed to match.
[1] I don't know if it's actually "unlimited" or not.
--
Brandon McCaig <http://www.bamccaig.com/> <bamcc...@gmail.com>
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Castopulence Software <http://www.castopulence.org/> <bamcc...@castopulence.org>
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