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Find the common items in two lists

Given two lists, find the common items. E.g. given beans = ['broad', 'mung', 'black', 'red', 'white'] and colors = ['black', 'red', 'blue', 'green'], what are the bean varieties that are also color names?
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ocaml
let beans = ["broad"; "mung"; "black"; "red"; "white"]

let colors = ["black"; "red"; "blue"; "green"]

let f common c = if List.mem c beans then c::common else common

let common = List.fold_left f [] colors;;

(* common will contain a list with the common elements *)
DiskEdit
ocaml
(* using standard (functorized) sets *)

module SetTools(ASet: Set.S) =
struct
let of_list l =
List.fold_left (fun acc e -> ASet.add e acc) ASet.empty l

let find_common l1 l2 =
ASet.elements (ASet.inter (of_list l1) (of_list l2))
end

module StringSet = Set.Make(String)

module StringSetTools = SetTools(StringSet)
;;
let beans = ["broad"; "mung"; "black"; "red"; "white"] in
let colors = ["black"; "red"; "blue"; "green"] in
StringSetTools.find_common beans colors;;

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