NAME

Sub::Memoized - trait for memoizing calls to subroutines

SYNOPSIS

use Sub::Memoized;

sub a($a,$b) is memoized {
  # do some expensive calculation
}

sub b($a, $b) is memoized( my %cache ) {
  # do some expensive calculation with direct access to cache
}

use Hash::LRU;
sub c($a, $b) is memoized( my %cache is LRU( elements => 2048 ) ) {
  # do some expensive calculation, keep last 2048 results returned
}

sub d(Int:D $a, Int:D $b) is memoized({ "$_[0],$_[1]" }) {
  # do some expensive calculation with cheaper key maker
}

sub e(Str:D $a, Str:D $b) is memoized(my %cache, *.list.sort.join("'")) {
  # do some expensive calculation with direct access to cache
  # without making the order of the arguments matter
}

DESCRIPTION

The Sub::Memoized distribution provides a is memoized trait on Subroutines as an easy way to cache calculations made by that subroutine (assuming a given set of input parameters will always produce the same result).

Optionally, one can specify an Associative that will serve as the cache. This allows later access to the generated results. Or you can specify a specially crafted hash, such as one made with Hash::LRU.

IDENTIFICATION KEY

By default, the identification key used to lookup values in the cache, is built from the .WHICH values of all the arguments passed to the subroutine. This may not always be the fastest or best way to do this.

Therefore one can specify a Callable that will be called to generate the identification key, bypassing the default key maker. This can e.g. be used to create a more efficient key generator, or can be used to create a key generator with special properties, e.g. making the arguments commutative.

This Callable will be given a Capture and is expected to return something that can be used as a key in the Associative that has been (implicitely) specified (usually a string).

CAVEAT

Please note that if you do not use a store that is thread-safe, the memoization will not be thread-safe either. This is the default.

AUTHOR

Elizabeth Mattijsen liz@raku.rocks

Source can be located at: https://github.com/lizmat/Sub-Memoized . Comments and Pull Requests are welcome.

If you like this module, or what I'm doing more generally, committing to a small sponsorship would mean a great deal to me!

COPYRIGHT AND LICENSE

This library is free software; you can redistribute it and/or modify it under the Artistic License 2.0.