rationalize bug

rationalize bug

[Bill Schottstaedt]

I hate to report a bug in my own handiwork, but I noticed
this morning, while writing a scheme numerics test suite
(numtst.c in the Snd tools directory), that if the error is
1.0, rationalize rounds the wrong way:

guile> (rationalize 0.1 1.0)
1.0
guile> (rationalize -0.9 1.0)
0.0

Rats.  I'll try to look at libguile/numbers.c soon.

Re: rationalize bug

[Ludovic Courtès]

Hello Bill,

"Bill Schottstaedt" <bil@ccrma.Stanford.EDU> writes:

> I hate to report a bug in my own handiwork, but I noticed
> this morning, while writing a scheme numerics test suite
> (numtst.c in the Snd tools directory), that if the error is
> 1.0, rationalize rounds the wrong way:
>
> guile> (rationalize 0.1 1.0)
> 1.0
> guile> (rationalize -0.9 1.0)
> 0.0
>
> Rats.  I'll try to look at libguile/numbers.c soon.

Any news on that?  :-)

Thanks,
Ludo'.

re: rationalize bug

[Bill Schottstaedt]

>> Rats.  I'll try to look at libguile/numbers.c soon.
> Any news on that?  :-)

No -- sorry -- my TODO list is so long, even emacs complains.

(There's a problem: the scheme spec seems to insist on the "simplest"
ratio which they define in terms of the size of the integers -- my 
rationalize used continued fractions so it's fast (worst case involves
successive fibonacci numbers, I think), but it's not always "simplest".
I think the scheme spec is silly -- this reminds me of (random 0.0)
in CL which is flagged as an error -- obviously CL-types have no idea
why you'd use random, and similarly for rationalize in scheme).