How to take product of two list in OCaml? -


i have 2 lists :

let = ["a";"b"]; let b = ["c";"d"];

i want output list c such :

c = ["a";"c";"a";"d";"b";"c";"b";"d"];

how in ocaml lists immutable? new it.

you return new list. if interested in cartesian product of lists, should enough: 

let cartesian l l' =    list.concat (list.map (fun e -> list.map (fun e' -> (e,e')) l') l)  # cartesian ["a";"b"] ["c";"d"];; - : (string * string) list = [("a", "c"); ("a", "d"); ("b", "c"); ("b", "d")]

if need strange flat structure instead, can use additional list concatenation. 

let flat_cartesian l l' =    list.concat (list.concat (     list.map (fun e -> list.map (fun e' -> [e;e']) l') l))

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