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[Caml-list] What's wrong with my parser ?
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Date: -- (:)
From: Nicolas FRANCOIS <nicolas.francois@f...>
Subject: Re: [Caml-list] What's wrong with my parser ?
OK, this is my new polynom parser, it seems to work OK, thanks to your
explanations.

  let rec parse s =
    let parse_puissance = parser
      | [< ''^'; e = parse_int >] -> e
      | [< >] -> 1
    in
    let parse_x = parser
      | [< ''X'; e = parse_puissance >] -> e
      | [< >] -> 0
    in
    let parse_coeff = parser
      | [< n = R.parse >] -> n
      | [< >] -> R.one
    in
    let parse_monome = parser
      | [< n = parse_coeff; e = parse_x >] ->
	  monome n e
      | [< e = parse_x >] ->
	  monome R.one e
    in
    let rec parse_suite = parser
      | [< ''+'; m = parse_monome; p = parse_suite >] ->
	  m ++ p
      | [< ''-'; m = parse_monome; p = parse_suite >] ->
	  (opp m) ++ p
      | [< >] -> zero
    in
      match s with parser
	| [< m = parse_monome >] ->
	    match parse_suite s with
	      | p -> m ++ p

and the results :

# print (P.parse (Stream.of_string "-1+3X+4X^2"));;
[3: -1, 3, 4]- : unit = ()
# print (P.parse (Stream.of_string ""));;
[1: 1]- : unit = ()

Oups !!

What do you think about this ?

\bye

-- 

                   Nicolas FRANCOIS
            http://nicolas.francois.free.fr
 A TRUE Klingon programmer does NOT comment his code
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