Using lambda expressions

We can rewrite our call to for as
for(0, fn x=>x+1, fn n=>n,
fn (x, y)=>x+y, 0)

We can do better, because
- Instead of fn (x, y)=>x+y, we can write op+
- We can write an auxiliary function for comparison

We can rewrite our call to for as for(0, fn x=>x+1, fn n=>n, fn (x, y)=>x+y, 0)