Hi all.

I must confess to being a little ashamed. Having worked with perl for a reasonable length of time, the concept of a closure should not prove to be so enigmatic. To alleviate my ignorance, I was hoping some of you could evaluate the code below and tell me what is happening at each stage of program execution. Granted, this is a very simple closure but in the event that someone asks me to explain how/why it works, I would probably provide an inadequate answer (at best). 

#!/usr/bin/perl -w
use strict;

sub shoppingList {

  my $item = shift();
  return sub
  {
    my $otherItem = shift();
    print "I need to buy a $item and a $otherItem.\n";
  };
}

my $itemInBasket = shoppingList( "sweater" );
my $newItemInBasket = shoppingList( "lipstick" );

&$itemInBasket( "pair of shoes" );
&$newItemInBasket( "purse" );

[download]


Thanks in advance for any help you are able to provide.

-Katie.

In reply to Help with the concept of closures. by DigitalKitty

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.