(* $Id: token.ml,v 1.5 1998/03/12 18:44:02 weis Exp $ *)

let I x = x;;

let keywords =
  let t = hashtbl__new 13 in
  hashtbl__add t "else" ELSE;
  hashtbl__add t "fi" FI;
  hashtbl__add t "if" IF;
  hashtbl__add t "let" LET;
  hashtbl__add t "then" THEN;
  t
;;

let buff = create_string 2000;;

(***
let rec ident len = function
  [<
    '(`a`..`z` | `A` .. `Z` | `0` .. `9` | `_` | `'`) as c;
    (set_nth_char buff len c; ident(succ len)) i
  >] -> i
| [< >] ->
    let str = sub_string buff 0 len in
    (try hashtbl__find keywords str with _ -> IDENT str)
;;
***)

let rec ident len = function
| [< '(`a`..`z` | `A` .. `Z` | `0` .. `9` | `_` | `'`) as c; s >] ->
    set_nth_char buff len c; ident (succ len) s
| [< >] ->
    let str = sub_string buff 0 len in
    (try hashtbl__find keywords str with _ -> IDENT str)
;;

let rec number n = function
| [< '`0` .. `9` as d; s >] ->
    number(10*n+int_of_char d-int_of_char`0`) s
| [< >] -> n
;;

let rec next_token = function
| [< '(`a`..`z` | `A` .. `Z`) as c; s >] ->
    set_nth_char buff 0 c; ident 1 s
| [< '`0` .. `9` as d; s >] ->
    INT(number (int_of_char d-int_of_char `0`) s)
| [< '` ` | `\n` | `\t`; s >] -> next_token s
| [< '`+` | `-` | `*` | `/` as c >] -> OP (make_string 1 c)
| [< '`.` >] -> DOT
| [< '`=` >] -> EQUAL
| [< '`\\` >] -> BSLASH
| [< '`;` >] -> SEMICOL
| [< '`(` >] -> LPAREN
| [< '`)` >] -> RPAREN
| [< 'x >] -> failwith ("Bad char: "^make_string 1 x)
;;

let rec reset_lexer = function
| [< '`\n` >] -> ()
| [< '_; reset_lexer _ >] -> ()
| [< >] -> ()
;;

let token_name = function
| IDENT _ -> "IDENT" | INT _ -> "INT" | OP _ -> "OP"
| BSLASH -> "\\" | DOT -> "." | ELSE -> "else" | EQUAL -> "="
| FI -> "fi" | IF -> "if" | LET -> "let" | LPAREN -> "("
| RPAREN -> ")" | SEMICOL -> ";" | THEN -> "then" 
;;