#13720: Scale legendre_P to [a,b]
-------------------------+-------------------------------------------------
Reporter: mjo | Owner: burcin
Type: | Status: needs_work
enhancement | Milestone: sage-5.13
Priority: major | Resolution:
Component: | Merged in:
symbolics | Reviewers: Francis Clarke, Karl-Dieter
Keywords: | Crisman
Authors: | Work issues:
Michael Orlitzky | Commit:
Report Upstream: N/A | Stopgaps:
Branch: |
Dependencies: |
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Comment (by mjo):
Replying to [comment:18 fwclarke]:
> I really don't understand why `a` and `b` get converted into symbolic
expressions. This has some very strange consequences, e.g.,
> {{{
> sage: legendre_P(3, 7, -1/2, 1/2).parent()
> Symbolic Ring
> }}}
> It is my understanding that coercion should arrange that the parent of
an expression is as close as possible to the parents of the constituant
parts. It is thus wrong to force (almost) everything into the Symbolic
Ring.
I had a comment in the code about this, but I've forgotten the details. In
any case -- whatever the issue was -- it seems to be fixed. I removed the
manual coercions of n,a,b and all of the tests still pass.
So this is fixed:
{{{
sage: legendre_P(3, 7, -1/2, 1/2).parent()
Rational Field
}}}
> Incidentally, in all cases there needs to be a check to see if `a == b`.
This will throw a divide-by-zero. What's the alternative?
--
Ticket URL: <http://trac.sagemath.org/ticket/13720#comment:19>
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