in reply to Serving many tarballs as part of your web space

I had the hardest time trying to understand the goings-on in this part of the script:
  for my $step (1..$#path) {
    @names = map /\A\/?\Q$path[$step]\E(?:\/(.*))?\z/s, @names;
    die "no such name" unless @names;
    if (grep !defined $_, @names) {

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I'm quite impressed.

Thanks for carving something useful out of my block of marble.

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Re: Re: Serving many tarballs as part of your web space
by jryan (Vicar) on Jan 11, 2002 at 14:12 UTC

    I'd imagine the map is the only part that is really confusing; here it is in a nutshell: 

    @names = map ( # start map

/ # start matching regex

# this will place what is matched in the grouping
# into $_, or undef if there are no matches

\A           # match start, kinda like ^,
             # except will ONLY match begining
\/  ?        # 0 or 1 literal backslashes
\Q           # start regex quotemeta 
$path[$step] # interpolated, and then quotemeta'd
\E           # end regex quotemeta
(?:          # non grouping parenthesis
\/           # literal backslash
(.*)         # here is what actually is grouped; 
             # matches the rest of the line
)?           # end non-grouping parens, 0 or 1 of those
\z           # match end, kinda like $,
             # except will ONLY match very end of string
/sx          # s lets . match newlines; i added the x
, @names);   # i added parenthesis

    [download]
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Re: Re: Serving many tarballs as part of your web space
by merlyn (Sage) on Jan 11, 2002 at 12:36 UTC
    The code I write for columns has far too few comments, because the comments are provided in the accompanying text. I think you'll see that it makes sense once you see the narrative I wrote for that particularly odd piece of code. I think I was trying to hard to be line-wise efficient.

    -- Randal L. Schwartz, Perl hacker

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      Figured so.

      After sleeping over it, I'm wondering if there's any particular reason you didn't something along the following lines?

      my ($prefix, $filepath) = split '/', $path, 2;

# ...

  @names = grep m!\A/?\Q$filepath\E(?:/.*)?\z!s, @names;

  if(@names == 1) {
    require Archive::Tar;
    # ...
    exit 0
  }

  {
    my %choices = ();
    # ...

      [download]

      The sole really significant difference I can see is that it doesn't catch the "trailing stuff after name" case. Am I missing something?

      Or should I just be patient and wait for the column? :-)

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