Re: Using the GNU GMP Library for Bignums in Emacs

[Paul Eggert]

> I read this thread and I still don't know what a use case for this would be.

Yes, I'm not seeing it either.

> it's simpler to explain that there are just integers.

Yes, and this is a significant win.

If interning bignums (so that eq works on them) is what it takes to satify 
Stefan's concerns, then I'm all for interning them. The idea is to avoid 
unnecessary distinctions between fixnums and bignums, so that Lisp programmers 
can focus on their problems rather than worry about integer representation. 
Although it's OK to have user-visible predicates fixnump and bignump for the few 
programmers who really need to know, I'm not seeing use cases for why these 
predicates should be any more special than characterp or natnump are.


>> why would someone want to specialize a method just for fixnums, as
>> opposed to a method for integers?
>
> cl-generic has no trouble dispatching on a supertype of that returned by
> `type-of`.

That's fine, but I was asking for use cases not implementation motivation. THat 
is, I was wondering why a Lisp programmer would want to use cl-generic that way. 
Having cl-generic distinguish fixnums from bignums sounds like more a solution 
looking for a problem than a truly useful feature.

>> The basic operations +, -, * etc. aren't specialized for fixnums.
>
> Actually, they are, but this is done by manual type-testing in the
> C code, not with cl-defmethod.

Yes, of course: with basic operations it's done under the hood, and Lisp 
programmers don't need to worry about the details. This is a reasonable 
programming style for Emacs Lisp, and it'd be a good thing if this style were 
used as consistently as possible, to keep things simpler.