On Sun, Jun 19, 2022 at 01:02:41AM -0700, 'Nasser M. Abbasi' via FriCAS -
computer algebra system wrote:
> I was looking at another question at difference forum. I noticed integrate
> hangs when
> using %i for sqrt(-1) but returns right away when type sqrt(-1). But
> returns with an error message.
<snip>
> So why this gives error
> ==========================
> (16) -> setSimplifyDenomsFlag(true)
>
> integrate(x/( (x^2 - 1/5 - 2*sqrt(-1)/5)*sqrt(x^3 - x)),x)
>
> There are 9 exposed and 6 unexposed library operations named -
> having 2 argument(s) but none was determined to be applicable.
> Use HyperDoc Browse, or issue
> )display op -
> to learn more about the available operations. Perhaps
> package-calling the operation or using coercions on the arguments
> will allow you to apply the operation.
>
> Cannot find a definition or applicable library operation named -
> with argument type(s)
> Polynomial(Fraction(Integer))
> AlgebraicNumber
>
> Perhaps you should use "@" to indicate the required return type,
> or "$" to specify which version of the function you need.
> ======================
This is weakness in machinery assigning types. Instead write:
integrate(x/((- 2*sqrt(-1)/5 + x^2 - 1/5)*sqrt(x^3 - x)),x)
And yes, addition should be commutative, but type assignment
works from left to right, so is noncommutative...
--
Waldek Hebisch
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