G'day rje,
Here's a solution using state, which therefore requires 5.10.0 or later:
$ perl -Mstrict -Mwarnings -E '
sub cycle {
state %i;
no warnings "uninitialized";
$_[0]->[($i{$_[0]} % @{$_[0]}, ++$i{$_[0]})[0]];
}
my $a2d = ["a" .. "d"];
my $e2h = ["e" .. "h"];
for (1..3) {
print cycle($a2d) for 1..3;
print cycle($e2h) for 1..3;
}
'
abcefgdabhefcdaghe
For earlier Perls, this uses a closure and retains the same level of privacy for %i:
$ perl -Mstrict -Mwarnings -E '
{
my %i;
sub cycle {
no warnings "uninitialized";
$_[0]->[($i{$_[0]} % @{$_[0]}, ++$i{$_[0]})[0]];
}
}
my $a2d = ["a" .. "d"];
my $e2h = ["e" .. "h"];
for (1..3) {
print cycle($a2d) for 1..3;
print cycle($e2h) for 1..3;
}
'
abcefgdabhefcdaghe
If you only ever want to cycle through a single array (I wasn't sure if that's what your OP was suggesting), then this would be faster (but has distinct limitations):
$ perl -Mstrict -Mwarnings -E '
sub cycle {
state $i = -1;
$_[0]->[++$i, $i %= @{$_[0]}];
}
my $stuff = ["a" .. "d"];
print cycle($stuff) for 1..30;
'
abcdabcdabcdabcdabcdabcdabcdab
Obviously, that can also be modified for earlier Perls in the same manner as the previous example.
|