Parsing with Sedlex and BatParserCo

gistfile1.ml

#!/usr/bin/env ocamlscript
Ocaml.ocamlflags := ["-g"; "-thread"];
Ocaml.use_camlp4 := false;
Ocaml.packs := ["batteries"; "sedlex"]
--
open Batteries

(* Sedlex lexer definitions *)
type token =
  | Number of int
  | Op_plus

let digit = [%sedlex.regexp? '0'..'9']
let number = [%sedlex.regexp? Plus digit]
let op_plus = [%sedlex.regexp? '+']

(* Lexer function *)
let rec token buf =
  match%sedlex buf with
  | number ->
      let n = int_of_string (Sedlexing.Utf8.lexeme buf) in
      Some (Number n, buf)
  | op_plus ->
      Some (Op_plus, buf)
  | Plus xml_blank ->
      token buf
  | eof ->
      None
  | _ ->
      assert false


(* BatParserCo parser definitions *)
let pnumber =
  let open ParserCo in
  satisfy (function
    | Number v -> true
    | _ -> false) |> label "number"

let pplus =
  let open ParserCo in
  exactly Op_plus |> label "op_plus"

let rec expr =
  let open ParserCo in
  pnumber >>> zero_plus (pplus >>> pnumber) >>> eof


let () =
  let buf = Sedlexing.Utf8.from_string "100 + 200" in
  let tokens = Enum.unfold buf token in
  let source = ParserCo.Source.of_enum tokens () (fun _ state -> state) in
  ParserCo.debug_mode := true;
  ParserCo.run expr source |> ignore