package tube

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Typesafe abstraction on top of Lwt_io channels

Install

Dune Dependency

Authors

Maintainers

Sources

4.4.0.tar.gz
md5=65e17606d445d517aad1f912daca4d88

Description

A typesafe abstraction on top of Lwt_io channels in order to avoid things like unsafe operations (i.e. https://github.com/ocsigen/lwt/issues/345 ) when running in practice.

Published: 11 Jul 2018

README

Ok, really nothing to see here, some Pipe abstraction on top of Lwt_io channels

Why did I do this thing, and not using directly Lwt_io channels (or even better, Async Pipes)?

Because of things like this https://github.com/ocsigen/lwt/issues/345
Quite easy to do it wrong, so for very basic operations when working with local data,
we can use this (I surely am), brings a little bit more of a type safety
into all that write/read value to channels.

How to build:

opam install jbuilder core lwt
make

How to use:

>  module Pipe = Tube.Make(struct type t = string end);;
module Pipe :
	sig
		type t = string
		type reader
		type writer
		val create : unit -> reader * writer
		val write : t -> writer -> unit Lwt.t
		val read : reader -> t Lwt.t
	end
> let (reader, writer) = Pipe.create ();;
val reader : Pipe.reader = <abstr>
val writer : Pipe.writer = <abstr>
> Pipe.write "something" writer;;
- : unit = ()
> Lwt.(Pipe.read reader >>= fun s -> Lwt_io.printlf "My fancy value: %s" s);;
My fancy value: something
- : unit = ()
> Pipe.write 911 writer;;
Error: This expression has type int but an expression was expected of type
				string

or, for write with pushback:

> let (reader, writer) = Pipe.create ();;
val reader : Pipe.reader = <abstr>
val writer : Pipe.writer = <abstr>
> Pipe.write_with_pushback "something" writer;;
(* This will block, when using inside of `utop`, till something reads from the created `reader`; *)
(* when doing this write in a different context than `utop`, the produced Lwt.t will not move on *)
(* until something will read from the `reader` *)

or, for custom data types:

> type roman_numeral = I | II | III | IV | V | VI | VII | VIII | IX | X;;
type roman_numeral = I | II | III | IV | V | VI | VII | VIII | IX | X
> module Pipe = Tube.Make(struct type t = roman_numeral end);;
module Pipe :
	sig
		type t = roman_numeral
		type reader
		type writer
		val create : unit -> reader * writer
		val write : t -> writer -> unit Lwt.t
		val read : reader -> t Lwt.t
	end
> let (reader, writer) = Pipe.create ();;
val reader : Pipe.reader = <abstr>
val writer : Pipe.writer = <abstr>
> Pipe.write IX writer;;
- : unit = ()
> Lwt.(Pipe.read reader >>= fun s ->
match s with
| IX -> Lwt_io.printl "9"
| _ -> Lwt_io.printl "Don't care...");;
9
- : unit = ()
> Pipe.write "not cool" writer;;
Error: This expression has type string but an expression was expected of type
				roman_numeral

Dependencies (3)

  1. lwt >= "2.4.7"
  2. dune >= "1.0"
  3. ocaml >= "4.04.0"

Dev Dependencies

None

Used by

None

Conflicts

None