sub foo {
    my $arg = shift @_;
    state %cache;

    return $cache{$arg} if exists $cache{$arg};

    return $cache{$arg} = something_costly( $arg );
}

[download]

Test code: 

use Immutable::UntestableCode qw( foo );

my $real_thing = \&Immutable::UntestableCode::something_costly;
my $calls = 0;
*Immutable::UntestableCode::something_costly = sub {
    $calls++;
    return $real_thing->( @_ );
};

foo( 1 );
is( 1, $calls );
foo( 1 );
is( 1, $calls );

[download]

- tye        

In reply to Re: How to test caching? (simple) by tye
in thread How to test caching? by JavaFan

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.