Question

What does the last line, return 1 + …. do ? How can you return 1 plus a function call?

Below is the assignments text:

These functions recursively count the number of instances of the key in the target string

def countSubStringMatchRecursive(target, key):
    currentPosition = find(target, key)
    if find(target, key) == -1:
        return 0
    else:
        return 1 + countSubStringMatchRecursive(target[currentPosition+1:], key) 

Answer 1

The last line isn’t returning “1 plus a function call”, it is returning 1 + the return value of the function, which is either 0 or 1 depending on whether the condition has been met.

It is recursive, in that the return value from the function call will be 1 + the return value of another function call — again, and again, and again, until find(target, key) == -1.

Think of it more like:

return 1 + ( 1 + (1 + (1 + (0))))