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Re: Using the GNU GMP Library for Bignums in Emacs

From: Paul Eggert
Subject: Re: Using the GNU GMP Library for Bignums in Emacs
Date: Tue, 10 Jul 2018 20:30:51 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0

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

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.

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