The concept of an iterator is a little different in Perl. You basically want to return a one-use subroutine “closed” over the persistent variables.
use bigint;
use strict;
use warnings;
sub fibonacci {
my $limit = 10**( shift || 0 );
my ( $a, $b ) = ( 0, 1 );
return sub {
return if $a > $limit;
( my $r, $a, $b ) = ( $a, $b, $a + $b );
return $r;
};
}
my $fit = fibonacci( 15 );
my $n = 0;
while ( defined( my $f = $fit->())) {
print "F($n): $f\n";
$n++;
}
And if you don’t like the while
loop, then here is two shots at some syntactic sugar, which basically accomplish an each-item loop.:
sub iterate ($$) {
my $iter = shift;
my $action = shift;
while ( defined( my $nextval = $iter->())) {
local *_ = \$nextval;
$action->( $_ );
}
return;
}
iterate fibonacci( 15 ) => sub { print "$_\n"; };
sub iter (&$) {
my $action = shift;
my $iter = shift;
while ( defined( my $nextval = $iter->())) {
local *_ = \$nextval;
$action->( $_ );
}
return;
}
iter { print "$_\n" } fibonacci( 15 );