Re: Using the GNU GMP Library for Bignums in Emacs

[Paul Eggert]

Siraphob (Ben) Phipathananunth wrote:
> One approach would be to implement a minimal subset of functions
> exposed in Emacs Lisp that would allow one to recreate the following
> functions that are defined in calc.el :

Surely we should just add bignum support to existing functions +, -, etc. 
Wouldn't that suffice for 'calc'? If not, why not? (Of course 'calc' would need 
to be changed to exploit the bignums properly, no matter how we add bignums.)

> With respect to floating points, though, things get a little hairy. 

This should be a separate task. Bignums alone are quite a large-enough project. 
I'm not even sure we should do rationals.

> The /actual/ value of the bignum
> (internally, in C) would be a tagged pointer to the mpz_t data type
> stored somewhere so that it could be marked for GC

For bignums I would think that Emacs shouldn't use the mpz_t data type, as this 
would complicate garbage collection. Emacs can use the mp_limb_t data type and 
stick with the mpn_* functions.