At 10:44 AM 5/17/01 +1000, King, Jason wrote:
>so here's the thing .. Perl doesn't have pointers .. only references .. so
>you can't have a 1500 element array and grab a reference to the 700th
>element
Oh yes you can:
my @foo = qw(three blind mice);
my $elemref = \$foo[2];
> .. because references don't work that way .. pointers work that way
>- but there aint no pointers in Perl
But as you say, you can't make a reference to a slice; you end up with a
list of references to each element of the slice. Pity.
Confirming that passing slices to subroutines results in copying:
$ perl -le 'system "ps -lp $$"; @x = 1..1_000_000; system "ps -lp
$$";foo(@x[1..500_000]); system "ps -lp $$"; sub foo{}'
F S UID PID PPID C PRI NI ADDR SZ WCHAN TTY TIME CMD
000 S 500 30162 30128 96 68 0 - 16513 wait4 pts/0 00:00:04 perl
F S UID PID PPID C PRI NI ADDR SZ WCHAN TTY TIME CMD
000 S 500 30162 30128 54 70 0 - 19482 wait4 pts/0 00:00:08 perl
F S UID PID PPID C PRI NI ADDR SZ WCHAN TTY TIME CMD
000 S 500 30162 30128 51 69 0 - 19971 wait4 pts/0 00:00:08 perl
So your solution of passing a ref to the whole array looks optimal.
--
Peter Scott
Pacific Systems Design Technologies
http://www.perldebugged.com
