[gambit-list] ffi double constants

Álvaro Castro-Castilla alvaro.castro.castilla at gmail.com
Mon Feb 20 11:08:49 EST 2012


Yeah, but I fixed it. I've had this error before and it was because of
the precision, but this time wasn't. As I'm messing with Android, I
thought it might be happening again.
No worries :)




On Mon, Feb 20, 2012 at 5:00 PM, Mikael <mikael.rcv at gmail.com> wrote:
> What is the problem, you get a broken circle?
>
> Den 20 februari 2012 17:56 skrev Álvaro Castro-Castilla
> <alvaro.castro.castilla at gmail.com>:
>
>> I was using (* 2 (angle -inf.0))
>>
>> But anyway, the problem is elsewhere, precision is double.
>>
>> Thanks!
>>
>>
>>
>> 2012/2/20 Bradley Lucier <lucier at math.purdue.edu>:
>> >
>> > On Feb 20, 2012, at 6:42 AM, Álvaro Castro-Castilla wrote:
>> >
>> >>
>> >> Hi,
>> >>
>> >> I want to use the M_PI constant, which is defined in C as #define M_PI
>> >> 3.14159265358979323846, with 21 decimals. For the Cairo bindings, the
>> >> full precision is needed, because drawing a circle is done by drawing
>> >> an arc 2*M_PI long, and the algorithm only considers it a circle when
>> >> the 2*pi is passed with the proper precision.
>> >
>> > (* 8 (atan 1)) should give you 2*M_PI to 64-bit double precision, so
>> > this should work unless you're working with 80-bit long doubles.
>> >
>> >> What's the way to support this precision for the FFI bindings, so I
>> >> can pass that value to the affected functions as it is done in C
>> >> without a special wrapper function for each case?
>> >>
>> >> Best regards,
>> >>
>> >> Álvaro
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>
>
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