comment on

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.
[download]

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

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