package octez-libs

You can search for identifiers within the package.

in-package search v0.2.0

Package contains no libraries

The main purpose of this module is to be used with parametric types such as ('a, Empty.t) result. Such type is actually isomorphic to 'a (see get_ok function). This is useful if a module signature expects a generic ('a,'b) result type, but for some instantiation, 'b is actually empty. Here is a small example how such module can be used:

module type S = sig

    type error

    type 'a t

    val return : 'a -> 'a t

    val fail : error -> 'a t

    val bind : 'a t -> ('a -> 'a t) -> (error -> 'a t) -> 'a t end

  module M : S with type error = Empty.t and type 'a t = ('a,
Empty.t) result = struct

    type error = Empty.t

    type 'a t = ('a, Empty.t) result

    let return = fun x -> Ok x

    let fail = Empty.absurd

    let bind = fun data left _right -> match data with | Ok x ->
left x | Error err -> Empty.absurd err end

  let _ = let data = M.bind (M.return 5) (fun x -> M.return (x +
2)) (Empty.absurd) in assert (data |> Empty.get_ok = 7)

type t = |

This type has no canonical inhabitant (there is no terminating OCaml value which inhabits this type).

val get_ok : ('a, t) result -> 'a

get_ok r eliminates the impossible case. This function is total and does not raise any exception.

val absurd : t -> 'a

absurd empty allows constructing any type from the absurd case. This is useful to typecheck impossible branches, e.g.

Result.fold ~ok:(fun i -> i + 1) ~error:Empty.absurd (Ok 41)

Note that this particular example using `result` can be rewritten as:

let i = Empty.get_ok (Ok 41) in i + 1