MRAB <python@...> writes:
I prefer (b). The problem with requiring `start` for sequences of non-
objects is that you now have to go out and create a "zero object" of the
type as your other objects. The object class might not even have a concept
If the objects can be summed, shouldn't there also be a zero object? Does anyone have an example when that's not possible?
You're right MRAB, probably almost every object type that has a concept of "addition" will have a concept of a zero element.
BUT, that zero object has to be created by the user of `sum`, and that has two problems:
1. The user might not know from beforehand which type of object he's adding. Even within the same type there might be problems. What happens when the user is using `sum` to add a bunch of vectors, and he doesn't know from beforehand what the dimensions of the vectors are? How will he know if his zero element should be Vector([0, 0]) or Vector([0, 0, 0])
2. A smaller problem: The user has to actually create that zero object now, and for some objects the definition might be lengthy, adding needless complexity to the code.
Also, using the `start` has some overhead, for creating the zero object and calling __add__.