Re: rational arithmetic library?

taltman_at_noshpam.lbl.government
Date: 02/24/04 

Date: Tue, 24 Feb 2004 12:49:46 -0800

Rahul Jain <rjain@nyct.net> writes:

> taltman@noshpam.lbl.government writes:
>
>> 1) The fun of implementing rational arithmetic in Scheme from scratch
>> aside, is there a library already implemented?
>
> Most implementations of Scheme already have rationals. From what I
> gather, scheme doesn't require rationals, but requires certain
> relationships with other numerical types to hold, if those other types
> are implemented.

I took a second look at R5RS, and I realized my confusion; I guess my
current implementation-of-choice, Guile, doesn't support 'numerator',
'denominator', or 'rationalize'! So I tried some others:

*DrScheme: yes
*Guile: no
*Chicken: no
*Bigloo: yes
*Scheme48/Scsh: yes
*SCM: no

Is there any more definitive information about this kind of "optional
standard" across various Scheme implementations? Specifically, are
there implementations which internally represent the division of
integers as the creation of a rational number, with both the numerator
and the denominator being bignums? If there's a limit to an
implementation's ability to store rationals (due to the numerator
and/or the denominator being fixnums), then they're useless for the
scientific application I had in mind.

So I guess this is standard in CL. Does the HyperSpec mandate this?
And are both the numerator and the denominator required to be
represented as bignums? I read the HyperSpec, and it didn't seem to
mention either way...

Would I be better off just using a CAS like GNU Maxima?

~Tomer

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