On Aug 17, David T-G said:
>% That's good of you to show how you'd do it in another language (yes, even
>% if that language is PHP ;) ), because it clears up what you want to do.
>
>Indeed. It was the most succinct way to explain it :-)
This list (and many others) often receives questions about code without
ever showing even pseudo-code. PHP has similar-enough syntax to Perl, so
it's fine.
>The
>
> s{#(.*?)#}
>
>appears to look for my template strings. And so then the {}ge part looks
>similar to a standard s///ge, so that's probably where it's doing the
>real work.
Yes. I'm using s{}{} instead of s///. I prefer the use of {} delimiters
when I'm doing a s///e, because it better represents the "code" aspect of
the replacement.
>I can somewhat follow the work (thanks for your patience, if you're
>reading along with me). Based on a match like #NAME_FIRST# found in the
>first line, we're going to look up the value pointed to by that hash key
>in the xlate hash I built. I have to figure that
>
> { $xlate{$1} }
>
>means to return that to the caller, even though it isn't return()ed or
>print()ed or whatever.
Yes; perhaps I should have been more explicit and said 'return ...'.
>So then we get to the really confusing part... AIUI we matched
>
> #key#
>
>but here we either say that we should spit
>
> #key
>
>back out or the #$1 means something that I don't get.
Sorry, that was my typo. It should be
else { return "#$1#" }
That is, if the text found between #'s isn't a key in the hash, just
return the text with the #'s on either side of it.
>% my $keys = join '|', map quotemeta, keys %xlate;
>% # quotemeta() make's sure any regex-characters in the keys are escaped
>%
>% $string =~ s/#($keys)#/$xlate{$1}/g;
>
>It's that funky map thing, though. I don't have much experience with
>that :-)
A simple way to look at map() and grep() is that they are merely for-loops
that automatically build up a return list for you. Here's a brief look at
their equivalence:
@data = map { TRANSFORMATION } LIST;
# is
@data = ();
for (LIST) {
push @data, TRANSFORMATION;
}
# and
@data = grep { CONDITION } LIST;
# is
@data = ();
for (LIST) {
push @data, $_ if CONDITION;
}
Compounded to this is the fact that both functions can be called with an
EXPRESSION, rather than a BLOCK:
@halves = map $_/2, @numbers;
@halves = map { $_/2 } @numbers;
mean the same thing really. I used the 'expression' syntax.
>Oh, I think I get it... We're only pulling the keys out of %xlate, and
>we're quoting them to be safe. And you picked '|' for the join because
>that's a regexp or, right? So my expr ends up being like
>
> s/#(NAME_FIRST|NAME_LAST...)#/...
>
>and the replacement is the bucket value of the key in the hash. Hey,
>that's slick.
Exactly.
>So why the map? Is that just a way to apply quotemeta to each key in the
>hash?
Yes. If we wrote the map() as a for loop:
my @safe;
for (keys %xlate) {
push @safe, quotemeta; # it's default arg is $_
}
my $pattern = join '|', @safe;
--
Jeff "japhy" Pinyan [EMAIL PROTECTED] http://www.pobox.com/~japhy/
RPI Acacia brother #734 http://www.perlmonks.org/ http://www.cpan.org/
<stu> what does y/// stand for? <tenderpuss> why, yansliterate of course.
[ I'm looking for programming work. If you like my work, let me know. ]
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