Why subtract a value from itself (x - x) in Python?

Question

In NumPy functions, there are often initial lines that do checking of variable types, forcing them to be certain types, etc. Can someone explain the point of these lines in scipy.signal.square? What does subtracting a value from itself do?

t,w = asarray(t), asarray(duty)
w = asarray(w + (t-t))
t = asarray(t + (w-w))

source

Answer 1

I believe that this will make the final w and t have the same type. For example, if you start with float and int, you will end up with both being float arrays which is better for subsequent operations.