Beefy Boxes and Bandwidth Generously Provided by pair Networks
Don't ask to ask, just ask
 
PerlMonks  

comment on

( #3333=superdoc: print w/replies, xml ) Need Help??
It prints "Number is: 196, Integer part is: 195", but I would expect $x2 to be 196

Your expectation is unreasonable. (I know ... it seems like a reasonable expectation ... but it is not.)

First of all, note that (1.15*170)+0.50 cannot be exactly represented in a double.
This is mainly due to the fact that 1.15 cannot be exactly represented in a double.
When you assign a value of 1.15 to a double you are actually assigning the precise value 1.149999999999999911182158029987476766109466552734375.
And the expression (1.15*150)+0.50 evaluates to exactly 195.999999999999971578290569595992565155029296875.

Perl's print() function takes the action of rounding that value to 15 decimal digits. It does that for all floating point values - always to 15 decimal digits (unless perl's nvtype is other than "double") and always for a dubious reason.

So ... quite clearly, the integer portion of 195.999999999999971578290569595992565155029296875 is 195, and 195.999999999999971578290569595992565155029296875 rounded to 15 decimal places is 196.
And this agrees with the results that you obtained.

It leaves shaking my head in disbelief, too ... but that's the stupid way that perl's print() function has been doing it for a long time and, unfortunately, I can't see it doing anything differently any time soon.
A far saner approach would be for perl's print() function to have displayed the value 195.99999999999997 as happens with python3 and raku.
Note that, although you have questioned the printed value of $x2, it's actually the printed value of $x1 that's misleading.

Cheers,
Rob

In reply to Re: int() function by syphilis
in thread int() function by geoperl

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 scrutinizing the Monastery: (7)
    As of 2021-04-19 23:03 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      No recent polls found

      Notices?