[PATCH] Say explicitly that eq is useful for chars; xref number comparison, lispref

[Aidan Kehoe]

 Ar an t-ochtú lá is fiche de mí Bealtaine, scríobh Stephen J. Turnbull: 

 > QUERY
 > 
 > Aidan Kehoe writes:
 > 
 >  > 	also mention that #'eq gives t when passed identical integers
 > 
 > I don't think this is true when bignums are enabled because they do
 > not have an immediate representation. 

Indeed, it’s not. The docs I cross-reference (from Jerry?) call immediate
integers in a build with bignum support “integers” though, not fixnums, and
suggest reasonable contexts where one might still want to use #'eq. In
particular, it’s perfectly cromulent to say (eq X Y) where X is a literal
integer and Y is a bignum, since bignums with values less than (/ (lsh 1
INT_VALBITS) 2) should not escape to Lisp.

 > It's only true for fixnums, which do. It's true for characters, which
 > also have an immediate representation. You should a mention that this is
 > an implementation detail, although it's very unlikely to change. Unless
 > Emacs promises that this is true?

Their Lisp reference does, yes. 

 >  > +characters and integers with the same numeric are @code{eq}.  Under
 >                                                  ^
 > typo --------------------------------------------+

Thanks for the correction!

-- 
¿Dónde estará ahora mi sobrino Yoghurtu Nghé, que tuvo que huir
precipitadamente de la aldea por culpa de la escasez de rinocerontes?