Re: [Maxima-discuss] ev(XXX, numer) tests in the testsuite

[Raymond T. <toy...@gm...>]

On Wed, Feb 22, 2023 at 6:44 AM Barton Willis via Maxima-discuss <
max...@li...> wrote:

>
>
> There are some (too many, I’d say) tests in our testsuite that set *numer*
> to true and use* ev.*  Here is one of them:
>
>
>
>     ev(integrate(x^3/(exp(x)-1),x,0,inf),numer)
>
>
>
> First, given the unintended consequences of *ev*, I think it would be
> better to write this test as
>
>
>
>  block([numer : true],  integrate(x^3/(exp(x)-1),x,0,inf))
>

I think this makes sense, but it's so much easier to write it ev(foo,numer)
or just foo,numer;

Perhaps we should also update the manual examples not to do foo,numer or
ev(foo,numer).  For a couple of examples I saw, we could replace foo,numer
with float(foo).  Or maybe we could add a numer function that basically
does what your block statement does.


>
> Second, I think getting limit and integrate (likely others) to work for
> correctly when *numer* is true is more work than it’s worth.  You can set *
> numer *to false at the top level of these mostly symbolically-based
> functions only to have it change later on.  I have a few bits of code
> that allow Maxima to symbolically compute this integral:
>
>
>
> (%i4)     block([numer : false], integrate(x^3/(exp(x)-1),x,0,inf));
>
> (%o4)   %pi^4/15
>
>
> (Current Maxima gives a limit nounform for this definite integral.)
>
>
>
> But when numer is true, my code says the integral diverges—why? Well two
> terms that should exactly cancel don't—look at  first term with the
> coefficient of 1.11...x10^-16.
>
>
>
>  3" Enter "limit"
> "[1.110223024625157*10^-16*%pi^2*x^2+(-0.1166666666666667*%pi^4\-0.5*log(-1)^2*%pi^2-0.25*log(-1)^4),x,inf,think]
>
>
>
> I'll continue looking for the place where numer gets set to true (it is
> set to false at the top of the my limit code. But I'm tempted to change the
> test to
>
>
> float(integrate(x^3/(exp(x)-1),x,0,inf))
>
>
> --Barton
>
>
>
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-- 
Ray