Module Make.Either

Either type.

Either is the simplest and most generic sum/variant type: a value of ('a, 'b) Either.t is either a Left (v : 'a) or a Right (v : 'b).

It is a natural choice in the API of generic functions where values could fall in two different cases, possibly at different types, without assigning a specific meaning to what each case should be.

For example:

List.partition_map:
  ('a -> ('b, 'c) Either.t) -> 'a list -> 'b list * 'c list

If you are looking for a parametrized type where one alternative means success and the other means failure, you should use the more specific type Result.t.

type ('a, 'b) t = ('a, 'b) Stdlib.Either.t =
  1. | Left of 'a
  2. | Right of 'b

A value of ('a, 'b) Either.t contains either a value of 'a or a value of 'b

val equal : left:('a -> 'a -> bool) -> right:('b -> 'b -> bool) -> ('a, 'b) t -> ('a, 'b) t -> bool

equal ~left ~right e0 e1 tests equality of e0 and e1 using left and right to respectively compare values wrapped by Left _ and Right _.

val compare : left:('a -> 'a -> int) -> right:('b -> 'b -> int) -> ('a, 'b) t -> ('a, 'b) t -> int

compare ~left ~right e0 e1 totally orders e0 and e1 using left and right to respectively compare values wrapped by Left _ and Right _. Left _ values are smaller than Right _ values.