Re: Using the GNU GMP Library for Bignums in Emacs

[Paul Eggert]

Helmut Eller wrote:
> (format "%x" -1) => "3fffffffffffffff".

Any program that assumes that behavior is already unportable, since the 
expression returns "3fffffff" on 32-bit platforms.

The usual approach for this is to format negative numbers with a leading minus 
sign, so that (format "%x" -1) returns "-1". This is what Emac Lisp should have 
been doing anyway as it is more intuitive and more portable. Obviously there 
will be compatibility concerns here, and we'll need to address them.