Beefy Boxes and Bandwidth Generously Provided by pair Networks
We don't bite newbies here... much
 
PerlMonks  

Comment on

( #3333=superdoc: print w/ replies, xml ) Need Help??
General advice. Just because there are many ways to do it in Perl is not a reason for picking a less readable one. If you are not returning data from map, then you should write it like this:
$hash1{$_} = $hash2{$_} for keys %hash2;
That is easier to read, and much more clearly signals intent. It is also at least as fast as the map version. (It used to be a lot faster, but in Perl 5.8 there is an optimization that causes map to shortcircuit to become a for if it is in null context.)

Furthermore performance is far less likely to matter than most people think, and when it does having micro-optimized as you went is generally a bad strategy for getting it. (You want to keep code clean and then look for a better algorithm, or move a small section into C.) Therefore I would generally use the following strategy because it is even clearer, even though it is marginally slower on my machine (about 10% so):

@hash1{keys %hash2} = values %hash2;
And, of course, in the rare case that performance really mattered and I really wanted to work in Perl, it is fastest to avoid having to do 2 sets of hash lookups on %hash2:
$combined{$k} = $v while my ($k, $v) = each %hash2;

In reply to Re^2: Concerning hash operations (appending, concatenating) by tilly
in thread Concerning hash operations (appending, concatenating) by RazorbladeBidet

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 cooling their heels in the Monastery: (20)
    As of 2014-07-29 13:58 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      My favorite superfluous repetitious redundant duplicative phrase is:









      Results (217 votes), past polls