Re: Using the GNU GMP Library for Bignums in Emacs

[Paul Eggert]

Stefan Monnier wrote:

> There's no need to explain the difference between `integer` and `bignum`
> here, just like we don't explain the difference between `subr` and
> `compiled-function`.

subr and compiled-functions are distinct (nonintersecting) types, whereas bignum 
is a subset of integer, so these are quite different cases. The manual says 
"each object belongs to one and only one primitive type; ‘type-of’ tells you 
which one". But if type-of returned 'integer' and bignums are integers (which 
they should be), this statement in the manual would become false, and would need 
to be rewritten. I don't see this as a win.

> I think I'm missing a reality check here.  We are talking about
> `type-of`, right?  Have you looked at how many times it's used in Elisp?

True, it's pretty rare. And it is a relic of the old-fashioned days when types 
were all disjoint. (Maybe we should remove 'type-of'? :-)

I'm not all that worried about type-of. I am more worried about the idea that 
bignums are second-class integers. When at all possible, bignums should be 
treated the same way that any other (large) integer is treated. For example, 
aref should report that a bignum index is out of range (if it is indeed out of 
range) rather than reporting a type error.