On Mon, Jul 04, 2005 at 08:34:26PM +0000 Vineet Pande wrote:
> Hello!
> In the following code:
>
> **************************************************
> #!/usr/bin/perl
> use warnings;
> use strict;
> my @unsorted = (1, 2, 11, 24, 3, 36, 40, 4);
> my @number = sort { $a <=> $b } @unsorted;
> print "Numeric sort: @number\n";
> **************************************************
> returns 1 2 3 4 11 24 36 40
>
> what I don't understand is how the block functions here: we did not define
> $a and $b? Also I donot understand this kind of block usage.
>
> Any comments appreciated!
in
Perl literacy course
lecture #5
Sorting and Perl
Shlomo Yona <[EMAIL PROTECTED]> http://cs.haifa.ac.il/~shlomo/
----------------------------------------------------------------------------
$a and $b
$a and $b are two elements of the list being compared during some iteration.
To optimize the calling of the sortsub, Perl bypasses the usual passing of
arguments via @_, using instead a more efficient special-purpose method.
Within the sortsub, the special package global variables $a and $b are
aliases for the two operands being compared.
The sortsub must return a number less than 0, equal to 0, or greater than 0,
depending on the result of comparing the sortkeys of $a and $b.
-----------------------------------------------------------------------------
hth
--
Gérard
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
<http://learn.perl.org/> <http://learn.perl.org/first-response>
