Eff (programming language)

Eff is a general-purpose, high-level, multi-paradigm, functional programming language similar in syntax to OCaml which integrates the functions of algebraic effect handlers.^[1][2]

Eff

Paradigms	Multi-paradigm: functional, imperative
Family	ML: Caml: OCaml
Designed by	Andrej Bauer, Matija Pretnar
First appeared	March 5, 2012; 13 years ago (2012-03-05)
Stable release	5.1 / October 19, 2021; 3 years ago (2021-10-19)
Implementation language	OCaml
Platform	x86-64
OS	Cross-platform: macOS, Linux, Windows
License	BSD 2-clause
Website	www.eff-lang.org
Influenced by
OCaml

Example

effect Get_next : (unit -> unit) option
effect Add_to_queue : (unit -> unit) -> unit

let queue initial = handler
  | effect Get_next k ->
    ( fun queue -> match queue with
        | [] -> (continue k None) []
        | hd::tl -> (continue k (Some hd)) tl )
  | effect (Add_to_queue y) k -> ( fun queue -> (continue k ()) (queue @ [y]))
  | x -> ( fun _ -> x)
  | finally x -> x initial
;;