FAQ 4.2 Why is int() broken?

Discussion in 'Perl Misc' started by PerlFAQ Server, Jan 13, 2011.

  1. This is an excerpt from the latest version perlfaq4.pod, which
    comes with the standard Perl distribution. These postings aim to
    reduce the number of repeated questions as well as allow the community
    to review and update the answers. The latest version of the complete
    perlfaq is at http://faq.perl.org .

    --------------------------------------------------------------------

    4.2: Why is int() broken?

    Your "int()" is most probably working just fine. It's the numbers that
    aren't quite what you think.

    First, see the answer to "Why am I getting long decimals (eg,
    19.9499999999999) instead of the numbers I should be getting (eg,
    19.95)?".

    For example, this

    print int(0.6/0.2-2), "\n";

    will in most computers print 0, not 1, because even such simple numbers
    as 0.6 and 0.2 cannot be presented exactly by floating-point numbers.
    What you think in the above as 'three' is really more like
    2.9999999999999995559.



    --------------------------------------------------------------------

    The perlfaq-workers, a group of volunteers, maintain the perlfaq. They
    are not necessarily experts in every domain where Perl might show up,
    so please include as much information as possible and relevant in any
    corrections. The perlfaq-workers also don't have access to every
    operating system or platform, so please include relevant details for
    corrections to examples that do not work on particular platforms.
    Working code is greatly appreciated.

    If you'd like to help maintain the perlfaq, see the details in
    perlfaq.pod.
    PerlFAQ Server, Jan 13, 2011
    #1
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    FAQ 4.2 Why is int() broken?

    PerlFAQ Server, Apr 25, 2011, in forum: Perl Misc
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