How to use function composition for `foo (bar x) (bar y)` in Haskell?

Question

I know that in Haskell, there is a awesome feature called function composition so that we could make our Haskell code pithier, like:

• use (f . g) x instead of f (g x),
• use foo x $ bar y z instead of foo x (bar y z)

But is it possible that we could use function composition for foo (bar x) (bar y)?

Answer 1

You can use the on function for this, for instance

import Data.Function

data Person = Person{name::String, age::Int}

compare `on` age --same as `\x y -> compare (age x) (age y)`