Beefy Boxes and Bandwidth Generously Provided by pair Networks
There's more than one way to do things

Comment on

( #3333=superdoc: print w/replies, xml ) Need Help??
The thing that surprises me though is that trying to increment the hash keys doesn't die like this one:

I agree, it seems odd. Consider:

#! perl use strict; use warnings; use Data::Dump; my %h = (1 => 'Fred'); dd %h; fn(%h); dd %h; sub fn { print "BEGIN fn()\n"; dd @_; $_[0]++; $_[1] = 'Barney'; dd @_; print "-END- fn()\n"; }


12:02 >perl (1, "Fred") BEGIN fn() (1, "Fred") (2, "Barney") -END- fn() (1, "Barney") 12:02 >

The hash value is clearly aliased, since the assignment in sub fn persists in %h after the sub returns. But the hash key is not: it appears to be copied (passed by value), as $_[0] behaves as a variable local to sub fn. (Whereas a literal value like 42 or 'Wilma' is aliased, as evidenced by the Modification of a read-only value error message which results from trying to increment it or assign to it within the sub.)

An anomaly? Or a feature?

Athanasius <°(((><contra mundum Iustus alius egestas vitae, eros Piratica,

In reply to Re^2: Alias of hash-values? by Athanasius
in thread Alias of hash-values? by LanX

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.
  • Log In?

    What's my password?
    Create A New User
    and all is quiet...

    How do I use this? | Other CB clients
    Other Users?
    Others browsing the Monastery: (8)
    As of 2018-06-20 18:10 GMT
    Find Nodes?
      Voting Booth?
      Should cpanminus be part of the standard Perl release?

      Results (117 votes). Check out past polls.