Beefy Boxes and Bandwidth Generously Provided by pair Networks
go ahead... be a heretic
 
PerlMonks  

comment on

( #3333=superdoc: print w/replies, xml ) Need Help??
I think that checking whether the UV arg == (UV)((NV)arg) is a splendid idea

Unfortunately this check fails for some UV values with less recent Microsoft Compilers - eg Visual Studio 2010 and earlier.
No problems with Visual Studio 2017 and Visual Studio 2019.
I suspect that Visual Studio 2015 is the oldest Microsoft Compiler that doesn't suffer from this problem, but I haven't confirmed that.

This particular issue looks like another manifestation of the problem that sent me down this path in the first place.
Here's the demo I ran:
use strict; use warnings; use Inline C => Config => BUILD_NOISY => 1; use Inline C => <<'EOC'; int uv_fits_double1( UV arg ) { if(arg == (UV)((NV)arg)) return 1; return 0; } int uv_fits_double2(UV arg) { while(!(arg & 1)) arg >>= 1; if(arg < 9007199254740993) return 1; return 0; } EOC my $ls = 63; my @in = ( 18446744073709549568, 18446744073709139968); for(@in) { print "$_: ", uv_fits_double1($_),uv_fits_double2($_), "\n" +; } __END__ With Windows Server 2003 SP1 Platform SDK, this outputs: 18446744073709549568: 01 18446744073709139968: 01 Base 2 representations of the 2 Uvs is (resp): 1111111111111111111111111111111111111111111111111111100000000000 1111111111111111111111111111111111111111111110011011100000000000 showing that both are exactly representable by a double.


Cheers,
Rob

In reply to Re^3: Detecting whether UV fits into an NV by syphilis
in thread Detecting whether UV fits into an NV by syphilis

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 exploiting the Monastery: (6)
    As of 2020-12-04 20:38 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?
      How often do you use taint mode?





      Results (62 votes). Check out past polls.

      Notices?