On Nov 19, 5:31 pm, Mike Witt <[email protected]> wrote:
> sage: assume(n, 'odd')
> sage: assumptions()
> [n is odd]
> sage: foo=sin((-1)*n*pi)
> sage: foo.simplify()
> 0
> sage: forget(n, 'odd')
> sage: assumptions()
> []
> sage: foo=sin((-1)*n*pi)
> sage: foo.simplify()
> 0
I'm guessing that Sage punts to Maxima for this stuff.
For better or worse (mostly worse) there are different ways
to declare & undeclare stuff in Maxima.
For the "odd" declaration, it's declare(n, odd) and remove(n, odd).
I guess assume(n, 'odd') was translated to declare(n, odd) but
forget(n, 'odd') was not translated to remove(n, odd).
I don't know much about Sage so I could be way off here.
A long-range goal for me anyway is to unify various declarations.
I see a couple of possibilities. One is FOO(P(x)) where P is some
predicate e.g. x is an integer, x is odd, x is less than 10, ...
(and FOO is a suitable imperative like "assume", "let", or "declare").
The other is FOO(x in A) where A is a set, which could be a symbol
like Z, R, or C, or a description like {x s.t. x < 10} or an
enumerated set.
i guess both could be recognized but I wonder whether one or the other
should be the canonical representation. (I wouldn't be surprised if a
lot
of ink has been spilled about this problem but I am pretty naive.)
If anyone has an opinion about it I would be interested to hear it.
FWIW
Robert Dodier
(a Maxima developer)
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