Interaction between floats and rational expression code.

Rupert Swarbrick wrote:

<snip>

> Anyway, I then realised that functions like RATTIMES don't preserve this
> "convention". For example, in the middle of a trace I get
>
>     1: (RATTIMES (1.2 . 1.0) (1 . 2) NIL)
>     1: RATTIMES returned (1.2 . 2.0)
>   

Given the circumstances, rattimes should be returning  (0.6   .   1)
On the other hand, I would prefer that ratsubst check that keepfloat is 
NOT True.  It can do this by giving an error message, or
alternatively, binding $keepfloat to nil.  An appropriate note in the 
documentation of ratsubst could make it clear how it reacts to 
keepfloat:true.

Why not patch rattimes?

Because the notion of reduction to lowest terms, when there are floating 
point numbers around, is a little vague.
Also checking innumerable times for a setting of a flag that, in all 
likelihood, represents a user error, seems to me
to be esthetically unpleasing.

RJF (who programmed rattimes, once upon a time)


> Is there a way to deal with floats sensibly in the rational expressions
> code? And, if so, can anyone explain which bit went wrong in the
> original reported bug?
>
>
>
> Rupert
>
>
> [1] http://sourceforge.net/tracker/?func=detail&aid=1928142&group_id=4933&atid=104933
>   
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