For those of a nervous disposition, reasurance your Perl code is actually processing something is a good thing. When writing code executed from the command line a spinner is a popular choice of providing this reassurance. When I first thought about doing this (many moons ago) I produced the following code:
my $i = 0;
my @spinner = ("|\r", "/\r", "-\r", "\\\r");
while (<>) {   # or any other looping structure
  print STDERR $spinner[$i];
  $i = $i++ % @spinner;
  # do stuff
}

[download]
After a while, and much learning, I realised I could shorten this to print STDERR $spinner[$i++ % @spinner]. I then went away happy thinking that was the best anyone could do. Until the other day. Out of the blue the following code "popped" into my head:
sub spinner {
  my $i; my @chars = defined @_ ? @_ : ("|\r", "/\r", "-\r", "\\\r");
  return sub { "$chars[$i++ % @chars]" };
}
my $spinner = spinner();
while (<>) {
  print STDERR $spinner->();
  # do stuff
}

[download]
I see this as an improvement on my last attempt for the following reasons:
1) It's more modular so I can have multiple spinners within one script, all giving different output (not sure when you'd want this mind!)
2) proves I have at least got a reasonable grip on how closures work
3) it is only fractionally slower than just printing $spinner[$i++ % @spinner]
I'd be interested in anyone elses thoughts on this code and any suggestions on how to do this differently/"better"/whatever

!unlike
"The price if ignorance, which is of course that you must learn from those with knowledge." Scorates (paraphrased)

In reply to Way of the Spinner (repost) by !unlike

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