Learning Functional Programming in Go

Non-TCO recursive example

First, we'll look at the imperative example:

rSum :: [Integer] -> IntegerrSum (x:xs) = x + (rSum xs)rSum [] = 0

Note that x:xs means we store the head of the list in x and the rest of the list is in xs.

Our goal: To recursively sum the numbers in the list [1, 2, 3].

Each call to rSum needs to get the return value of the recursive call and add it to its x parameter before it can return. This means that each function must stay on the stack longer than the frame of any function that it calls. We had to create four stack frames to sum three numbers. Imagine the amount of RAM storage that this implementation will require ...