I looked at this posibility also. The problem is that if a user
creates a rational expression as
rat(expr, v1, v2 ... vn) the variables v1..vn are kept in the head of
the expression and showratvars has to go thru the expression anyway
to make sure that these variables are really in the expression.
Since that has to be done anyway, the freeof checking should be
done while the expression is gone thru.
Dan Stanger
willisb@unk.edu wrote:
>
> When p is a *polynomial* or a *rational* expression, maybe something
> like
>
> ratfreeof(x,p) := not (member(x, showratvars(p)));
>
> would be a fast way to check if a CRE expression p depends on x. I may
> be
> wrong, but I think that showratvars doesn't convert to general form.
> If p isn't polynomial or rational, ratfreeof will misbehave; I think
> this
> could be repaired.
>
> I haven't carefully followed this thread, so ignore me if I'm in left
> field.
>
>
> Barton