How to convert a string to integer list in ocaml?

Question

I need to pass two list as command line arguments in ocaml. I used the following code to access it in the program.

let list1=Sys.argv.(1);;
let list2=Sys.argv.(2         


        

Answer 1

As Sys.argv is a string array, you need to write your own transcription function.

I guess the simplest way to do this is to use the Genlex module provided by the standard library.

let lexer = Genlex.make_lexer ["["; ";"; "]"; ]
let list_of_string s =
  let open Genlex in
  let open Stream in
  let stream = lexer (of_string s) in
  let fail () = failwith "Malformed string" in
  let rec aux acc =
    match next stream with
    | Int i ->
      ( match next stream with
        | Kwd ";" -> aux (i::acc)
        | Kwd "]" -> i::acc
        | _ -> fail () )
    | Kwd "]" -> acc
    | _ -> fail ()
  in
  try
    match next stream with
    | Kwd "[" -> List.rev (aux [])
    | _ -> fail ()
  with Stream.Failure -> fail ()

let list1 = list_of_string Sys.argv.(1)
let list2 = list_of_string Sys.argv.(2)

Depending on the OCaml flavor you want to use, some other library may look more interesting. If you like yacc, Menhir may solve your problem in a few lines of code.