escape

gadt-escape.ml

type _ grammar =
  | Either : 'a grammar list -> 'a grammar
  | CharLiteral : char -> char grammar

type state

type 'a result = Ok of 'a | Failure of string

type 'a parser_code = state code -> 'a result code

type 'a parser_generator =
  'a grammar -> 'a parser_code

let gen_charlit_parser : char -> char parser_code = assert false
let gen_either_parser: ('a parser_code) list -> 'a parser_code = assert false

let rec gen_parser : type a. a parser_generator = fun c state ->
  match c with
  | CharLiteral c -> gen_charlit_parser c state
  | Either grammar_list ->
    gen_either_parser (List.map gen_parser grammar_list) state

error message given by compiler does not help at tall