A transitory variable is a variable that isn't used for anything other than to schlep data from one line to another. (I'm not sure the term is right, but I think it's what you mean. I call 'em "useless variables", myself.) In other words, if I'm going to say:

my $foo = get_foo(); do_something($foo);
Then $foo is a transitory variable. It would be just as simple, and less error-prone, to say:
do_something( get_foo() );

Why? Because variables can and should vary. It doesn't seem like such a big deal when the assignment and the use of the variable are right next to each other, but what if they get separated?

my $foo = get_foo(); if ($snargle = 3 && $foo = 2) { whatever($snargle, $foo); # lots of other stuff here... } do_something($foo);

Oops, on line 2 up there we changed the value of $foo. Also, it makes refactoring harder-- what if you wanted to pull out the stuff inside the if statement into its own subroutine? It'd be simpler if you didn't have $foo there at all, and just called get_foo() when you needed a foo-value.

In your code, @for_data, @map_data, @sort_data, and @grep_data are all transitory variables. Ironically, @last_elements is not... you're using it to collect elements! Nothing wrong with that.

As for why slce_with_sort() and slice_with_grep() aren't doing what you expect, it's because sort and grep don't do what you apparently think they do. :) The block argument to grep is a test block, not a filter block. So the statement

grep { $_->[2] } @slice_me;
means, "If the item at index 2 of @$_ evaluates to true, return $_." The last bit is important-- it doesn't return the item at index 2, it returns the whole thing. A similar thing is happening with sort. You're sorting each row based on the value of the last column, and returning a list of the rows. Since the values are identical, it doesn't even change their order. :)

So where did you get that water? Sounds like powerful stuff. :)

stephen


In reply to Re: seeking different ways to slice a 2-d array by stephen
in thread seeking different ways to slice a 2-d array by belden

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, 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
  • 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.