Re: Perl Syntax that we generally don't know or forget.

Lvalue substr() is my special friend. Did you know you can bind regular expressions and transliterations to them?

  my $x = "x" x 50;
  substr($x, 12, 34) =~ tr[x][y];
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Foreach's iterator variable is an alias for an item in the list being iterated through. This works with values() and hash slices, too.

  my %x = (a=>1, b=>2, c=>3);
  $_ *= 2 foreach values %x;
[download]

I'm so, so easily amused. :)

-- Rocco Caputo - rcaputo@pobox.com - poe.perl.org

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•Re: Re: Perl Syntax that we generally don't know or forget. by merlyn (Sage) on Jan 18, 2004 at 13:13 UTC
No! Don't stop there! You can also use the lvalue bindings of argument passing! Three nested lvalue usages: `my $value = "abcde"; sub attack { $_[0] = "x" } attack($_) for substr($value, 2, 1); print "$value\n"; # prints "abxde\n"` [download] And if I understood lvalue subroutines better, I could probably write "attack($_) = 'x'" instead, for a fourth layer. {grin} -- Randal L. Schwartz, Perl hacker Be sure to read my standard disclaimer if this is a reply.	[reply] [d/l]
Re: •Re: Re: Perl Syntax that we generally don't know or forget. by shotgunefx (Parson) on Jan 18, 2004 at 18:15 UTC
Like this?. Or is there something I'm missing here.. `sub attack :lvalue { substr($_[0], 2, 1) ; }` [download] -Lee "To be civilized is to deny one's nature."	[reply] [d/l]
Re: Re: •Re: Re: Perl Syntax that we generally don't know or forget. by ysth (Canon) on Jan 19, 2004 at 02:12 UTC
That is supposed to work, but currently has some problems (see perl bug #24200) if you call attack in an rvalue context after calling it in an lvalue context.	[reply]
substr() as an lvalue by ambrus (Abbot) on Jan 19, 2004 at 11:37 UTC
Wow, I didn't know that. You can even `$a="abcdef"; substr($a,2,-2) x= 3; print $a,$/;` that prints abcdcdcdef. This is amazing. And you can buy 2 cats as simple as: `$_="I have 2 dogs and 9 cats.\n"; /(\d+)\s+cat/ or die; substr($_,$-[1],$+[1]-$-[1])+= 2; print;` which prints `I have 2 dogs and 11 cats.'. See also Re: cut of first char of a string.	[reply] [d/l] [select]