NAME

Pointy::Counter - funny syntax for loops

SYNOPSIS

use Pointy::Counter;

my $i = counter;
while ($i --> 10)
{
  say "\$i is $i";
}

# says $i is 1
# says $i is 2
# ...
# says $i is 10

DESCRIPTION

Pointy::Counter is a class that provides objects which seem to act like numbers, but have a special --> operator to count up to a particular value.

OK, confession time... --> is not really an operator. It's a post-increment followed by a greater than sign.

$i --> 10

is parsed by Perl like:

($i--) > 10

Then the Pointy::Counter class overloads -- to increment rather than decrement, and overloads > to act as a less-than. If you try to perform any other maths, it should just act as a normal scalar. In particular, note that this means that while $i-- will do a counter increment; $i -= 1 will act completely differently, decrementing the counter and restoring it to a normal Perl scalar.

Constructor

Pointy::Counter->new($initial)

Creates a new counter, with the initial value (defaults to 0). Note that the counter will have value $initial before the loop starts, but within the body of the loop, it will be $initial+1, $initial+2, etc.

counter $initial

This module exports a function which can be called as a shortcut for the constructor.

Methods

value

Returns current value as a plain old Perl scalar. This is an lvalue subroutine, so you can, for example, reset a counter using:

$i->value = 0;

continue

Really does decrement the counter. This is used to solve a small niggling problem:

my $x = counter;	
while ($x --> 2)
{
  say "Counter is $x (loop A)";
}
while ($x --> 4)
{
  say "Counter is $x (loop B)";
}

Will output:

Counter is 1 (loop A)
Counter is 2 (loop A)
Counter is 4 (loop B)

Why doesn't it output a line for when its value is 3? That's because it only takes the value 3 between the two loops. The solution is to decrement the counter before starting loop B:

my $x = counter;	
while ($x --> 2)
{
  say "Counter is $x (loop A)";
}
$x -> continue;
while ($x --> 4)
{
  say "Counter is $x (loop B)";
}

This gives you:

Counter is 1 (loop A)
Counter is 2 (loop A)
Counter is 3 (loop B)
Counter is 4 (loop B)

BUGS

Please report any bugs to http://rt.cpan.org/Dist/Display.html?Queue=Pointy-Counter.

SEE ALSO

overload, perlsyn.

AUTHOR

Toby Inkster <tobyink@cpan.org>.

COPYRIGHT AND LICENCE

This software is copyright (c) 2011 by Toby Inkster.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

DISCLAIMER OF WARRANTIES

THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.