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Perl function: state
With state (and use 5.10.0) it's possible to declare static variables, that is, variables that are initialized only once.
Thus, a function can have its own »state«.
The following example shows a function that every time it is called calculates the average, count, min and max of the numbers passed to the function.
#!/usr/bin/perl
use warnings;
use strict;
use 5.10.0;
min_max_avg(15);
min_max_avg( 5);
min_max_avg( 7);
sub min_max_avg {
state $min = +"Inf";
state $max = -"Inf";
state $sum = 0;
state $cnt = 0;
print " min | max | cnt | avg\n" unless $cnt;
my $num = shift;
$sum += $num;
$cnt ++;
$min = $num if $num < $min;
$max = $num if $num > $max;
printf " %3d | %3d | %3d | %3d\n", $min, $max, $cnt, $sum/$cnt;
}
# min | max | cnt | avg
# 15 | 15 | 1 | 15
# 5 | 15 | 2 | 10
# 5 | 15 | 3 | 9