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Lazy::Static

cpan:SAMGWISE

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NAME

Lazy::Static - Lazy calculation of static values

SYNOPSIS

use Lazy::Static;

# Something for our lazy static closure to pick from
my @options = <foo bar baz>;

my &result = lazy-static -> {
    sleep 2; # Some long running calculation;
    @options.pick
}

# It's thread safe
my @threads = start {
    say result; # This will be the same value, since the generator will only be called once.
} for 1..16;

say "Awaiting execution of lazy-static generator...";
await Promise.allof: @threads;

say '-' x 78;

# We can call it without the wait now, since now the result has been calculated
say result;

DESCRIPTION

Lazy::Static is a thread-safe alternative to the the state keyword for working with static values.

AUTHOR

Sam Gillespie samgwise@gmail.com

COPYRIGHT AND LICENSE

Copyright 2019 (c) Sam Gillespie

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

sub lazy-static

sub lazy-static(
    &generator
) returns Mu

Creates a closure which lazily returns the result of the generator provided. The generator Callable is executed the first time the closure is called and all calls afterwards will receive the the value from the first call. If the result of the generator is never required it will never be generated. A value generated in a lazy-static closure will persist until it is garbage collected, like a normal scalar.