let increment n = n+1;;

let x = increment -5;;

let x = increment -5;;
        ^^^^^^^^^
Error: This expression has type int -> int
       but an expression was expected of type int`

let increment n = n + 1
let x = increment @@ -5

let increment n = n + 1
let x = -5 |> increment
let clamp x low high = x |> min high |> max low