MSVC: fix for failing tests due to strtod+hexadecimal literals

[Dan Olson via digitalmars-d-ldc]

"Johan Engelen" <j at j.nl> writes:

> On Tuesday, 3 March 2015 at 22:12:39 UTC, Dan Olson wrote:
>>
>> Could David Gay's strtod() be used?
>> http://www.exploringbinary.com/how-strtod-works-and-sometimes-doesnt/
>
> Thanks for that link. I had a look at David Gay's strtod() (a
> complicated piece of code) and it also accepts hex floats [1].
> I think it is clear that my hex parser is much simpler but also
> more naive and may need quite some extra complication to make it
> deal with all corner cases (I am by no measure an expert on IEEE
> fp). Although a fun exercise, I guess I should accept the fact
> that David Gay's function is very much superior to mine :)
>
> Should we replace MSVC's strtod() altogether with David Gay's, or
> use only the hex parser "gethex()"?

Personally I don't know but it does look like the gethex() function
could be used.  I would think whatever is easiest to keep going and
passes unittests.  BTW, David Gay is listed as the author in BDS man
page for strtod (uses by OS X).

Another thing.  Kai has worked on using LLVM'S own float (APFloat)
support class.  Seem to me like this will eventually be the best way to
go as it does all this and will be consistent across platforms.  Clang
appears to use this to parse float literals (I just grepped the source).

P.S. exploringbinary is a fun website.