Recursion

Let's say you know how to climb one step:

function step_up(step):
	hwup!

How do you climb a staircase?

Iteratively:

function climb(stairs):
	for each step in stairs:
		step_up(step)

Recursively:

function climb(stairs):
	step_up(the first step)
	climb(the rest of the stairs)

TODO:

• head and tail recursion
• why should we care?