jocaml

JoCaml is an experimental functional programming language derived from OCaml. It integrates the primitives of the join-calculus to enable flexible, type-checked concurrent and distributed programming. The current version of JoCaml is a re-implementation of the now unmaintained JoCaml made by Fabrice Le Fessant, featuring a modified syntax and improved OCaml compatibility compared to the original.

JoCaml was used by team Camls 'R Us to implement a distributed ray tracer, earning 2nd place on the ICFP 2000 programming contest.

The name is a reference to Joe Camel, a cartoon camel used in advertisements for Camel-brand cigarettes.

Example

type coins = Nickel , Dime
and drinks = Coffee , Tea
and buttons = BCoffee , BTea , BCancel;;

(* def defines a Join-pattern alternatives set clause
* '&' in the left side of '=' means join (channel synchronism)
* '&' in the right hand side is parallel processing
* synchronous_reply :

"reply" "to" channel_name
* synchronous channels have function-like types (`a -> `b)
* while asynchronous ones have type `a Join.chan
* only the last statement in a pattern rhs expression can be an asynchronous message
* 0 in an asynchronous message position means STOP ("no sent message" in CSP terminology).
*)

def put(s) = print_endline s ; 0 (* STOP *)
;; (* put: string Join.chan *)

def give(d) = match d with
Coffee -> put("Coffee")
, Tea -> put("Tea")
;; (* give: drink Join.chan *)

def refund(v) = let s = Printf.sprintf "Refund %d" v in put(s)
;; (* refund: int Join.chan *)

let new_vending give refund =
let vend (cost:int) (credit:int) = if credit >= cost
then (true, credit - cost)
else (false, credit)
in
def coin(Nickel) & value(v) = value(v+5) & reply to coin
or coin(Dime) & value(v) = value(v+10) & reply to coin

or button(BCoffee) & value(v) =
let should_give, remainder = vend 10 v in
(if should_give then give(Coffee) else 0 (* STOP *))
& value(remainder) & reply to button

or button(BTea) & value(v) =
let should_give, remainder = vend 5 v in
(if should_give then give(Tea) else 0 (* STOP *))
& value(remainder) & reply to button

or button(BCancel) & value(v) = refund( v) & value(0) & reply to button
in spawn value(0) ;
coin, button (* coin, button: int -> unit *)
;; (* new_vending: drink Join.chan -> int Join.chan -> (int->unit)*(int->unit) *)

let ccoin, cbutton = new_vending give refund in
ccoin(Nickel); ccoin(Nickel); ccoin(Dime);
Unix.sleep(1); cbutton(BCoffee);
Unix.sleep(1); cbutton(BTea);
Unix.sleep(1); cbutton(BCancel);
Unix.sleep(1) (* let the last message show up *)
;;

execution

$ jocamlc example.ml -o test
$ ./test
Coffee
Tea
Refund 5

See also

*Join-calculus

References

External links

The join-calculus language

The JoCaml system

Concurrent programming languages
OCaml programming language family
Programming languages created in the 1990s

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