Re: strange 1+/1- bug?

[rls@hoiho.math.waikato.ac.nz (Richard Shepherd)]

Bruno Haible wrote:
> 
> Of course. The CLISP compiler recognizes that (+ x 1) is equivalent to
> (1+ x) and thus generates a tail-recursive call, just as if you had written
>   (defun 1+ (x) (1+ x)).

Ah, how silly of me!

> > Is this a bug that is fixed in later versions?
> 
> No, this isn't a bug. You are not allowed to modify built-in Common Lisp
> functions (see CLtL2 or dpANS), and that's what the warning was about.

Aha, I did not know this either.  Can you tell me *where* in CLtL2 it
says this?  I have been looking but with no success yet.  As it turns
out I don't need to play with 1+ anyway.  I thought incf may use it
but it doen't seem to, i.e. (incf x) seems to work, even when x is not
a number, in my code.  So I'll leave it there.

> Using CLOS for arithmetic operations provides a great flexibility.

It certainly does, everything (in the arithmetic sense) seems to be
fine now, cheers,

8<--------------------------->8
Richard Shepherd. 
(rls@math.waikato.ac.nz)