package ppx_monad

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A Syntax Extension for all Monadic Syntaxes

Install

Dune Dependency

Authors

Maintainers

Sources

v0.2.0.tar.gz
md5=80638269b3f82227706ea6873209adde
sha512=a1b84d2b837439c47db55d229ca3a48ef99a75b95917d6b615c61fd324001ad7243f71f198002f25022bb4348bef656184eb56e5223d687a7b3a5ed049c8ba33

doc/src/ppx_monad_ppx_either/ppx_monad_ppx_either.ml.html

Source file ppx_monad_ppx_either.ml

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open Ppxlib

let mk_return ~loc x =
  [%expr Stdlib.Either.Right [%e x]]

let mk_bind ~loc e f =
  let (px, x) = Ppx_monad_lib.fresh_variable () in
  let (py, y) = Ppx_monad_lib.fresh_variable () in
  [%expr
    match [%e e] with
    | Stdlib.Either.Right [%p px] -> [%e f] [%e x]
    | Stdlib.Either.Left [%p py] -> Stdlib.Either.Left [%e y]]

let mk_fail ~loc y =
  [%expr Stdlib.Either.Left [%e y]]

let mk_catch ~loc e f =
  let (px, x) = Ppx_monad_lib.fresh_variable () in
  let (py, y) = Ppx_monad_lib.fresh_variable () in
  [%expr
    match [%e e] with
    | Stdlib.Either.Right [%p px] -> Stdlib.Either.Right [%e x]
    | Stdlib.Either.Left [%p py] -> [%e f] [%e y]]

let () = Ppx_monad_lib.register "either.right"
    ~applies_on:"either|(either.)?right"
    ~mk_return ~mk_bind
    ~mk_fail ~mk_catch

let () = Ppx_monad_lib.register "either.left"
    ~applies_on:"(either.)?left"
    ~mk_return:mk_fail
    ~mk_bind:mk_catch
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