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(* ocamlc -c -I +camlp4 -pp 'camlp4o pa_extend.cmo q_MLast.cmo' pa_printf.ml *)

let make_printf _loc format =
  let parse_format format =
    let rec lit e s = parser
    | [< ''%'; strm >] -> esc <:expr< compose $e$ (lit $str:s$) >>  "" strm
    | [< 'c; strm >] -> lit e (s  ^ String.make 1 c) strm
    | [< >] -> <:expr< compose $e$ (lit $str:s$) >>
    and esc e s = parser
    | [< ''d'; strm >] -> lit <:expr< compose $e$ int >> "" strm
    | [< ''f'; strm >] -> lit <:expr< compose $e$ float >> "" strm
    | [< ''c'; strm >] -> lit <:expr< compose $e$ char >> "" strm
    | [< ''s'; strm >] -> lit <:expr< compose $e$ str >> "" strm
    | [< ''%'; strm >] -> lit <:expr< compose $e$ (lit "%") >> "" strm
    in
    lit <:expr< fun x -> x >> "" (Stream.of_string format)
  in
  let parsed_format = parse_format format in
  <:expr<
    let compose f g x = f (g x) in
    let lit x k s = k (s ^ x) in
    let int k s x = k (s ^ string_of_int x) in
    let str k s x = k (s ^ x) in
    let float k s x = k (s ^ string_of_float x) in
    let char k s x = k (s ^ String.make 1 x) in
    let format p = p (fun s -> s) "" in
    format $parsed_format$
  >>
;;

EXTEND
  Pcaml.expr: LEVEL "expr1" [
    [ "myprintf"; format = STRING -> make_printf _loc format ]
  ];
END