On Sun, May 19, 2013 at 8:58 PM, Julien Rioux <julien.ri...@gmail.com> wrote:
>
> On Sunday, 19 May 2013 20:31:07 UTC-4, Aaron Meurer wrote:
>>
>> I'm writing the part of the new tutorial on solve(). I have some
>> questions
>>
>> - What is a good example of an equation that has a solution, but which
>> cannot be represented symbolically (as an example of when solve()
>> might return no solutions for this reason)?
>>
>
> solve(sin(x)) only returns 0 instead of infinitely many pi-periodic
> solutions:
>>>> solve(sin(x))
> [0]
>
> This can be represented symbolically with a parameter but we don't do it
> yet. As a result we get this behavior:
>>>> solve(sin(x)/x)
> []
>>>> solve(sin(Symbol('x', nonzero=True)))
> []
>
> So solve returns an empty list.
Except I don't think it's that great to advertise what SymPy can not
do in the tutorial.
Aaron Meurer
>
>>
>> [...]
>>
>> - The lack of a consistant return type is killing me. It seems the
>> type depends not just on whether you are solving one or two equations,
>> but also on the *type* of the equations!
>>
>> In [5]: solve([x - 1, y - 1], [x, y])
>> Out[5]: {x: 1, y: 1}
>>
>> In [6]: solve([x**2 - 1, y - 1], [x, y])
>> Out[6]: [(-1, 1), (1, 1)]
>>
>> Is there a reason that we don't set `dict=True` by default, at least
>> for systems of equations?
>>
>
> Since I discovered it, I always use dict=True and have never looked back. In
> a tutorial I would use dict=True everywhere.
>
> Cheers,
> Julien
>
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