Reason · Reason lets you write simple, fast and quality type safe code while leveraging both the JavaScript & OCaml ecosystems.

sig
 external id : 'a -> 'a = "%identity"
 val const : 'a -> 'b -> 'a
 val flip : ('a -> 'b -> 'c) -> 'b -> 'a -> 'c
 val negate : ('a -> bool) -> 'a -> bool
 val protect : finally:(unit -> unit) -> (unit -> 'a) -> 'a
 exception Finally_raised of exn
end