Beefy Boxes and Bandwidth Generously Provided by pair Networks
Clear questions and runnable code
get the best and fastest answer
 
PerlMonks  

Comment on

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

This raises another question though: this is fairly simple and understandable (and in this case, Perl doesn't DWIM), how should it be written instead?

$c_old = $c; $c+=$_; [$c_old, $c]; is quite cumbersome. ($c = $c_old = $c) += $_; is just messing with peoples' head;. So I thought "Well, the unary + has a high precedence, and it's actually just the identity operator, this should work just fine":

perl -MData::Dumper -E 'say join ", ", +$c,$c+=1 for 1..3'

1, 1 2, 2 3, 3
I thought I had missed something, but because I did have an idea of what was happening I thought "well, I'll just try it with two - instead"

perl -MData::Dumper -E 'say join ", ", --$c,$c+=1 for 1..3'

0, 0 0, 0 0, 0
Yup, stupid, -- is not two unary -, but one auto-decrement operator. So:

perl -MData::Dumper -E 'say join ", ", - -$c,$c+=1 for 1..3'

0, 1 1, 2 2, 3
Talking about clear code ... So I guess hazylife's version is actually the best: $c+0,$c+=$_; with a comment at the end so that the next person reading the code does not think "Oh, +0, now that's silly, let's just remove it!"

But still, +$c should work shouldn't it? What happens is obvious, perl just "optmises" it away as soon as it sees it. That's still an inconsistency, because you can't just replace a unary - with a unary + and expect the things to happen in the same order. I could only try that in perl v5.14, but I suppose it's still the case in later versions, could someone try it?


In reply to Re: Why does the first $c evaluate to the incremented value in [$c, $c += $_] ? by Eily
in thread Why does the first $c evaluate to the incremented value in [$c, $c += $_] ? by smls

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 wandering the Monastery: (6)
    As of 2014-10-25 11:25 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      For retirement, I am banking on:










      Results (143 votes), past polls