Re: [Fastlibnt-devel] mp_limb_t

[David H. <dmh...@ma...>]

On Apr 17, 2007, at 6:46 PM, William Hart wrote:

> I can't believe this is an unsigned type. So when we
> use it for limbs in Zpoly_mpn_t the sign limb can't be
> compared to 0 to see if it is negative. Instead I have
> to specifically do a comparison with -1L. That's kind
> of crap because it means we can't just use any old
> negative number for a negative sign. It has to be a
> specific number so that we can do an easy comparison.

Well, there's also mp_limb_signed_t (or perhaps it's  
mp_signed_limb_t? i can't remember), but that doesn't really help  
you, since the array has to be of a single type.

Perhaps it's worth having macros

COEFF(poly, n)

which returns a pointer to the limbs of the nth coefficient of poly,  
and also

SIGN(poly, n)

which returns the sign limb of the nth coefficient, casted to a  
signed type.

Not sure if those are the right names for the macros, but something  
like that would certainly simplify a lot of the Zpoly_mpn code.

david