Beefy Boxes and Bandwidth Generously Provided by pair Networks
laziness, impatience, and hubris
 
PerlMonks  

Comment on

( #3333=superdoc: print w/ replies, xml ) Need Help??

Break it up peice by peice.

pair takes a "hash" and creates an AoA. Consider this code:

my @got = pair( . . . );

Where $i is any integer between 0 and scalar(@got), $got[$i][0] will contain the "hash" key, and $got[$i][1] will contain its value.

Taking the map statements in order of execution, the first one is:

my @got2 = map { [$_->[0],$_->[1],'meowmoo'] } @got;

@got2 is also an AoA, but this time containing three elements. The first two are exactly as they are in @got, and the thrid one is always 'meowmoo'.

The second map statement is a bit trickier:

my @got3 = map { &{$_->[1]}($_->[2]) ? $_->[0] : () } @got2;

This one needs to be broken up further:

&{$_->[1]} # Get the subroutine referanced in $got2[$i][1] ($_->[2]) ? # Pass in the value of $got2[$i][2] ('meowmoo') $_->[0] : # If the subroutine returned true, then # pass back the key of the "hash" associated # with that subroutine. () # Otherwise, return undef

@got3 is a simple array, and will contain ('cat', undef, 'cow'). Actually, I'd have to run the code to check if that undef is really there. Hopefully, this is a multiple-choice test and answers with and without the undef are not both present :) If I had to choose, I'd say that it would be.

----
I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident.
-- Schemer

Note: All code is untested, unless otherwise stated


In reply to Re: Teaching Perl by hardburn
in thread Teaching Perl by Ovid

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!
  • 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, 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, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • Outside of code tags, you may need to use entities for some characters:
            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.
  • Log In?
    Username:
    Password:

    What's my password?
    Create A New User
    Chatterbox?
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others taking refuge in the Monastery: (5)
    As of 2014-07-23 04:55 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      My favorite superfluous repetitious redundant duplicative phrase is:









      Results (133 votes), past polls