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??

The oft-cited list of values considered false is:

  • undef
  • 0
  • ""
  • "0"
  • Any blessed objects that overload conversion to boolean to return false
  • Empty lists and empty hashes

I did actually manage to find another value that Perl treats as false:

-0.0

You can see its interesting behaviour here:

perl -E'say(-0.0 eq 0?"eq 0":"ne 0"); say(-0.0?"true":"false");' ne 0 false

Note that it's false but not (stringy) equal to zero.

This does vary between Perl versions. The behaviour documented above exists between Perl 5.6.x to 5.12.x (obviously you need to use print instead of say before Perl 5.10) and perhaps earlier. But in Perl 5.14.x, -0.0 is (stringy) equal to 0.

perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'

In reply to Re: What is true and false in Perl? by tobyink
in thread What is true and false in Perl? by root

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 making s'mores by the fire in the courtyard of the Monastery: (7)
    As of 2014-12-25 12:35 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      Is guessing a good strategy for surviving in the IT business?





      Results (160 votes), past polls