On Thursday 13 May 2010 07:05:31 C.DeRykus wrote:
> On May 12, 1:15 pm, fulls...@me.com (Brian) wrote:
> > Hi all. I think this should be relatively simple but i just can't figure
> > it out. I have a list of files and directories. The files will all end
> > in .html. All the remaining elements in the list are assumed to be
> > directories. I'm looking for a regex to add a trailing slash to the
> > directories if one doesn't exist. I can do this but using a series of if
> > statements, but I am trying to make my code more concise by using the
> > map function. Here is an example:
> >
> > my @pages = (
> > "lc1",
> > "lc2/",
> > "lc3/index.html",
> > "lc4/",
> > "lc5",
> > );
> >
> > map {s/(some regex here)/$1\//} @pages;
>
> Although newer perl versions can use map in void context
> without penalty, it's clearer to use a for loop IMO:
>
> map { s{ ([^/]) \z }{ "$1/" }xe if -d } @pages;
>
> vs.
>
> for (@pages ) { s{ ([^/]) \z }{ "$1/" }xe if -d };
>
Indeed, clarity is the key point here. "map" is intended to generate a new
list of items from an existing list (possibly to map an array to a different
array) while keeping the original items intact. "for"/"foreach" are useful
when you're interested in modifying the elements or for side-effects (like
printing them).
From the same reason, I prefer to use List::MoreUtils' "any" function (and
related functions such as "none", "all" and "notall") instead of doing games
with "if (!grep { .. } )" or List::Util's "!defined(first ...)" - it better
conveys my intention.
Regards,
Shlomi Fish
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