Should Call support functions without arguments?

[pimvenderbosch]

Follows up on the discussion in #7.
For the Call object a decision should be made if functions are supported without arguments.
Does the following code make sense:

instuctions = [
    Assign("%N", Call("some_func"))
    ⠇
]

Related to this: are functions with void returns allowed. This could be supported by adding Call objects as possibility in Model.instructions: list[QuInstruct | Assign | Call].

[pimvenderbosch]

After a discussion with @kaosmicadei, we concluded that there possibly are use cases for function calls without passing any arguments. Use cases include, but not limited to:

• Random number generation
• Using default values
• Get some information from elsewhere

In our opinion, void returns shouldn't be allowed. If a function doesn't need to return something, the result can be ignored.

#7 already implements the behavior described above, so this issue will be closed.