a 'with' statement for perl

A source filter implementation of with found in other languages, where the given argument becomes a topicalizer for the given block, or if it's a bareword the block will be in the bareword's namespace e.g

use With;

my $foo = "a string";

print "before with: $foo\n";
with($foo) {
  s/a /not a /;
}
print "after with:  $foo\n";

with(foo) {
  sub new {
    bless {}, shift;
  }
}

print foo->new;

__output__

before with: a string
after with:  not a string
foo=HASH(0x80fbbf0)
[download]

Disclaimer: the above code was inspired by a CB conversation

package With;

use strict;

use Regexp::Common;
use Filter::Simple;

FILTER_ONLY
  code => sub {
    s[ with \s* ( $RE{balanced}{-parens => '()'} ) \s* { ]
     < 
       my($t) = $1 =~ /\((.*)\)/;
       $t =~ /^[_a-zA-Z](?:(?:\w*)(?:(?:'|::)(?:\w+)+)?)*\z/ ?
         "{ package $t;"
        :
         "for($t) {"
     >iexsg;
  },
;

q{ they think it's all over, and now it is };
[download]

Comment on a 'with' statement for perl Select or Download Code

Replies are listed 'Best First'.
Re: a 'with' statement for perl by mirod (Canon) on Apr 25, 2003 at 11:59 UTC
It seems to me that the first part, using `with` to topicalize is exactly what `for` does: `#!/usr/bin/perl -w use strict; my $foo = "a string"; print "before with: $foo\n"; for($foo) { s/a /not a /; } print "after with: $foo\n";` [download] I believe that's indeed one of the reasons for the use of `for` as a keyword, instead or just `foreach`.	[reply] [d/l]
Re: Re: a 'with' statement for perl by broquaint (Abbot) on Apr 25, 2003 at 12:05 UTC
It seems to me that the first part, using `with` to topicalize is exactly what `for` does ... It is indeed, but `for`'s behaviour isn't obvious to many programmers coming from other languages (and yes, I know it's clearly documented in `perlsyn`). I should possibly also mention in the description that it was inspired out of a CB conversation, which explains away the obvious redundancy ;) HTH `_________ broquaint`	[reply]
Re: a 'with' statement for perl by demerphq (Chancellor) on Apr 26, 2003 at 15:48 UTC
Heh. I had the strangest feeling of deja-vu when I read this node. lol. --- demerphq _{<Elian> And I do take a kind of perverse pleasure in having an OO assembly language...}	[reply] [d/l]