Anybody want to try and explain this one?

I find this is a bit interesting.
I can reproduce it on perl-5.26.0 (nvtype=double): 
C:\>perl -le "printf '%.0f', 2e25;"
20000000000000001811939328
C:\>perl -le "printf '%.0f', 20e24;"
19999999999999997516972032

[download]
It happens because 20e24 is miscalculated (off by one ULP). It's an error that doesn't occur on all of my "double" perls. For example, my perl-5.16.0 is not subject to this issue.

UPDATE: Actually, it occurs on all of my "double" builds of perl that were built using an x86_64 compiler.
I also see the same bug on perl-5.26.0 on Linux (Ubuntu): 
$ perl -le 'printf "%.0f\n", 2e25;'
20000000000000001811939328
$ perl -le "printf '%.0f', 20e24;"
19999999999999997516972032

[download]

Odd that perl6 should have managed to inherit the same failing.
Are you using a current version of perl6 ?

Cheers,
Rob

In reply to Re: Small Perl 6 discoveries III, Ints by syphilis
in thread Small Perl 6 discoveries III, Ints by Anonymous Monk

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, details, 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, summary, 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.