I have encountered this independently, and it's a major source of headache.
Wouldn't a more useful representation of a(b) be something like
FunctionCall(a, b) [I obviously used FunctionCall a mock name here]? That
would allow to keep a in the list of atoms, and would create a
representation of the expression that is easier to parse.
While syntactically a function call does resemble a class instance, I
cannot think of useful applications of class hierarchy in this case. A
function doesn't implement any methods of its own, and so there is nothing
meaningful for its calls to reuse.
Does the above make sense?
On a more practical note, what is 'the official' way to get all the free
symbols from an expression, including functions? There's
expr.atoms(Function), but it's rather hard to parse, and the closest I got
to get the name from a(b).func.__name__ and check if type(type(a(b)) is and
UndefinedFunction.
Best,
Anton Akhmerov
On Monday, October 28, 2013 6:16:16 PM UTC+1, Aaron Meurer wrote:
>
> This is correct. type() in Python basically means "class of".
> Function('x') creates a class, called "x". When you apply it to t, it
> creates an instance of that class. The class of the class (i.e., metaclass)
> is UndefinedFunction.
>
> Aaron Meurer
>
> On Oct 28, 2013, at 11:01 AM, Jason Moore <moore...@gmail.com
> <javascript:>> wrote:
>
> I'm curious why x(t) in the following code doesn't display any type:
>
> In [9]: x = sympy.symbols('x', cls=sympy.Function)
>
> In [10]: type(x)
> Out[10]: sympy.core.function.UndefinedFunction
>
> In [11]: t = sympy.symbols('t')
>
> In [12]: t
> Out[12]: t
>
> In [13]: type(x(t))
> Out[13]: x
>
> Jason
> moorepants.info
> +01 530-601-9791
>
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