Hi,
Just wondering why ActiveState's 64-bit build of perl has
"use64bitint=define" but "uselongdouble=undef".
I have no doubt that there are good reasons - just wondering what they are
:-)
Whilst I have come across a number of builds of perl (linux, cygwin) that
were built with "use64bitint=define", I have not yet encountered a build
that supports long doubles.
The following script hints at my interest in seeing "uselongdouble=define".
-----------------------------------------
use warnings;
$v = 2 ** 57 + 12345; # 144115188075868217
{
use integer;
$w = 2 ** 57 + 12345;
}
if($w - 10 == $v - 10) {print "Correct\n"}
else {print "Wrong\n"}
$y = '144115188075868217';
$z = '144115188075868217rubbish';
{
no warnings 'numeric';
if($y == $z) {print "Correct\n"}
else {print "Wrong\n"}
}
-----------------------------------------
On my 64-bit build of ActivePerl 820, that script outputs:
Wrong
Wrong
I believe that, if perl were also built with "uselongdouble=define" then the
same script would output:
Correct
Correct
And, for me, the latter DWIMs better than the former.
I have a second (tenuously related) question. When I first wrote the above
test script I had:
if($w == $v) {print "Correct\n"}
else {print "Wrong\n"}
And that produced "Correct". Yet a Devel::Peek::Dump() reveals that $v is an
NV which, owing to loss of precision, could surely only contain the value
144115188075868224. Otoh, $w is an IV with the value 144115188075868217. I'm
still trying to work out how perl arrives at the conclusion that $w == $v.
(I then rewrote the code as '$w - 10 == $v - 10' simply because that
demonstrated the anomaly I was wanting to demonstrate.)
Cheers,
Rob
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