Re: Using the GNU GMP Library for Bignums in Emacs

[Paul Eggert]

Stefan Monnier wrote:
> Also, for purposes of cl-generic's dispatch it'd be better for type-of
> to return `natnum` or `fixnum` when applicable.
Isn't the issue of how finely type-of distinguishes integers separable from the 
issue of whether to have bignums? type-of could return 'natnum' now, even 
without bignums, but it doesn't. If we decide that type-of should return some 
value other than 'integer' for some integers, how would we decide what value to 
return? For example, if (natnump X) and (bignump X) both succeed, should type-of 
return 'natnum' or 'bignum' or both?

All in all I expect Elisp would be a bit easier to use and explain if it treats 
'integer' as the fundamental type, and 'characterp', 'fixnump', 'bignump', 
'natnump' as predicates that succeed on only some members of that type.

> it's indeed safer to just
> keep returning `integer` for small integers (and probably some other value
> for bignums, such as `bignum`).

Why the latter? That is, when would it be useful in existing code for (type-of 
X) to return a value other than 'integer' when (integerp X) returns t?