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: @numbern";
**************************************************
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!
cheers
v
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Full Version: "sort" usage in arrays
Vineet Pande [VP], on Monday, July 04, 2005 at 20:34 (+0000) wrote:
VP> what I don't understand is how the block functions here: we did not define
VP> $a and $b? Also I donot understand this kind of block usage.
when you don't know something, try ask perl:
perldoc -q sort
if you find (or know) functions name, try
perldoc -f sort
everything is explained there.
--
...m8s, cu l8r, Brano.
[A nudist is one who suffers from clothostrophobia.]
VP> what I don't understand is how the block functions here: we did not define
VP> $a and $b? Also I donot understand this kind of block usage.
when you don't know something, try ask perl:
perldoc -q sort
if you find (or know) functions name, try
perldoc -f sort
everything is explained there.
--
...m8s, cu l8r, Brano.
[A nudist is one who suffers from clothostrophobia.]
On Mon, Jul 04, 2005 at 08:34:26PM +0000 Vineet Pande wrote:
| QUOTE |
| 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: @numbern"; ************************************************** 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 Removed]> 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
--
Grard
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