Re^3: Detecting whether UV fits into an NV

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

Comment on Re^3: Detecting whether UV fits into an NV Download Code

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Re^4: Detecting whether UV fits into an NV
by pryrt (Abbot) on Feb 27, 2020 at 14:53 UTC

Data::IEEE754::Tools

#!/usr/bin/env perl

use strict;
use warnings;
use Data::IEEE754::Tools qw/ulp/;

sub uv_fits_double_using_ulp {
    0 == ($_[0] % ($_[0]/ulp($_[0])))
}

my @in = map { no warnings 'portable'; chomp; oct('0b'.$_) } <DATA>;

for(@in) {
    my $d = $_/ulp($_);
    printf "%-24s: %4d %32.15f %16d %1s\n", $_, ulp($_), $_/ulp($_), $
+_ % $d, uv_fits_double_using_ulp($_) ? 'T' : 'F';
}

__END__
1111111111111111111111111111111111111111111111111111100000000000
1111111111111111111111111111111111111111111111111111110000000000
1111111111111111111111111111111111111111111111111111100000000001
1111111111111111111111111111111111111111111110011011100000000000
1111111111111111111111111111111111111111111111111111100000000000
0111111111111111111111111111111111111111111111111111110000000000
0011111111111111111111111111111111111111111111111111111000000000
0001111111111111111111111111111111111111111111111111111100000000
0000111111111111111111111111111111111111111111111111111110000000
0000011111111111111111111111111111111111111111111111111111000000
0000001111111111111111111111111111111111111111111111111111100000
0000000111111111111111111111111111111111111111111111111111110000
0000000011111111111111111111111111111111111111111111111111111000
0000000001111111111111111111111111111111111111111111111111111100
0000000000111111111111111111111111111111111111111111111111111110
0000000000011111111111111111111111111111111111111111111111111111
0000000000111111111111111111111111111111111111111111111111111111
1111111111111111111111111111111111111111111111111111111111111111
[download]

18446744073709549568    : 2048 9007199254740991.000000000000000       
+         0 T
18446744073709550592    : 4096 4503599627370496.000000000000000 450359
+9627369472 F
18446744073709549569    : 2048 9007199254740991.000000000000000       
+         1 F
18446744073709139968    : 2048 9007199254740791.000000000000000       
+         0 T
18446744073709549568    : 2048 9007199254740991.000000000000000       
+         0 T
9223372036854774784     : 1024 9007199254740991.000000000000000       
+         0 T
4611686018427387392     :  512 9007199254740991.000000000000000       
+         0 T
2305843009213693696     :  256 9007199254740991.000000000000000       
+         0 T
1152921504606846848     :  128 9007199254740991.000000000000000       
+         0 T
576460752303423424      :   64 9007199254740991.000000000000000       
+         0 T
288230376151711712      :   32 9007199254740991.000000000000000       
+         0 T
144115188075855856      :   16 9007199254740991.000000000000000       
+         0 T
72057594037927928       :    8 9007199254740991.000000000000000       
+         0 T
36028797018963964       :    4 9007199254740991.000000000000000       
+         0 T
18014398509481982       :    2 9007199254740991.000000000000000       
+         0 T
9007199254740991        :    1 9007199254740991.000000000000000       
+         0 T
18014398509481983       :    4 4503599627370496.000000000000000 450359
+9627370495 F
18446744073709551615    : 4096 4503599627370496.000000000000000 450359
+9627370495 F
[download]

I doubt it's faster than some of hte others

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