Re: integer overflow

[Helmut Eller]

* Stefan Monnier [2010-03-06 16:45+0100] writes:

>>>> Can you summarize how it's supposed to work?
>>> The change affects the Lisp reader: reading "536870912" or any larger
>>> number now gives you a float Lisp object, instead of an integer Lisp
>>> object (since there is no way to represent 536870912 or larger as
>>> integers).  536870911 and below are still read as integers.
>> What's the point of doing that?  I would much prefer if read would just
>> raise an error.
>
> There are many cases where it's important to read an integer from some
> other program, so it's important to be able to read integers larger the
> Elisp's largest fixnum (tho less so for integers larger than the
> host system's natural "int").
> Examples are file sizes, process ids, user ids, ...

read doesn't seem the right tool for this job; read is for parsing Lisp
syntax.  Those few programs which produce Lisp syntax should probably
just write floats if there is a danger of overflow and precision doesn't
matter.  For those cases were precision does matter (eg. a 32bit Emacs
reading a file produced by a 64bit Emacs) I'd prefer an error instead of
automatic coercions.

Helmut