Beefy Boxes and Bandwidth Generously Provided by pair Networks
Your skill will accomplish
what the force of many cannot
 
PerlMonks  

comment on

( #3333=superdoc: print w/replies, xml ) Need Help??
Hello Great Monks! Could anyone explain why this program dies? "x" valu in hashref $h shouldn't be modified... in the same manner as "y" was not modified...
#!/usr/bin/perl -CSDA use utf8; use Modern::Perl qw{2017}; use Data::Dumper; $Data::Dumper::Sortkeys = 1; my $h = {a => 1, b => "", c => 2}; my $d1 = Dumper($h); printf "grep: %s\n", (join " ... ", grep { $_ } $$h{a}, $$h{x}, $$h{b +}, $$h{c}); printf "test: %s\n", $$h{y} ? "yes" : "no"; my $d2 = Dumper($h); $d1 eq $d2 or die "\nFAIL! h{x} modified, h{y} not modified... why?\n +\n$d1\n$d2";
result:
grep: 1 ... 2 test: no FAIL! h{x} modified, h{y} not modified... why? $VAR1 = { 'a' => 1, 'b' => '', 'c' => 2 }; $VAR1 = { 'a' => 1, 'b' => '', 'c' => 2, 'x' => undef };

In reply to unexpected modify hash in a distance with grep { $_ } by leszekdubiel

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.
  • 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: (4)
    As of 2020-11-25 06:12 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      No recent polls found

      Notices?