(*  Title:      Pure/ML/ml_lex.ML

    ID:         $Id$

    Author:     Makarius

Lexical syntax for SML.

*)

signature ML_LEX =

sig

  datatype token_kind =

    Keyword | Ident | LongIdent | TypeVar | Word | Int | Real | Char | String |

    Space | Comment | Error of string | EOF

  eqtype token

  val stopper: token Scan.stopper

  val is_regular: token -> bool

  val is_improper: token -> bool

  val pos_of: token -> string

  val kind_of: token -> token_kind

  val content_of: token -> string

  val keywords: string list

  val source: (Symbol.symbol, 'a) Source.source ->

    (token, (SymbolPos.T, Position.T * (Symbol.symbol, 'a) Source.source)

      Source.source) Source.source

end;

structure ML_Lex: ML_LEX =

struct

(** tokens **)

(* datatype token *)

datatype token_kind =

  Keyword | Ident | LongIdent | TypeVar | Word | Int | Real | Char | String |

  Space | Comment | Error of string | EOF;

datatype token = Token of Position.range * (token_kind * string);

(* position *)

fun position_of (Token ((pos, _), _)) = pos;

fun end_position_of (Token ((_, pos), _)) = pos;

val pos_of = Position.str_of o position_of;

(* control tokens *)

fun mk_eof pos = Token ((pos, Position.none), (EOF, ""));

val eof = mk_eof Position.none;

fun is_eof (Token (_, (EOF, _))) = true

  | is_eof _ = false;

val stopper =

  Scan.stopper (fn [] => eof | toks => mk_eof (end_position_of (List.last toks))) is_eof;

(* token content *)

fun content_of (Token (_, (_, x))) = x;

fun token_leq (tok, tok') = content_of tok <= content_of tok';

fun kind_of (Token (_, (k, _))) = k;

fun is_regular (Token (_, (Error _, _))) = false

  | is_regular (Token (_, (EOF, _))) = false

  | is_regular _ = true;

fun is_improper (Token (_, (Space, _))) = true

  | is_improper (Token (_, (Comment, _))) = true

  | is_improper _ = false;

(** scanners **)

open BasicSymbolPos;

fun !!! msg = SymbolPos.!!! ("SML lexical error: " ^ msg);

(* blanks *)

val scan_blank = Scan.one (Symbol.is_ascii_blank o symbol);

val scan_blanks1 = Scan.repeat1 scan_blank;

(* keywords *)

val keywords = ["#", "(", ")", ",", "->", "...", ":", ":>", ";", "=",

  "=>", "[", "]", "_", "{", "|", "}", "abstype", "and", "andalso", "as",

  "case", "datatype", "do", "else", "end", "eqtype", "exception", "fn",

  "fun", "functor", "handle", "if", "in", "include", "infix", "infixr",

  "let", "local", "nonfix", "of", "op", "open", "orelse", "raise", "rec",

  "sharing", "sig", "signature", "struct", "structure", "then", "type",

  "val", "where", "while", "with", "withtype"];

val lex = Scan.make_lexicon (map explode keywords);

fun scan_keyword x = Scan.literal lex x;

(* identifiers *)

local

val scan_letdigs =

  Scan.many ((Symbol.is_ascii_letter orf Symbol.is_ascii_digit orf Symbol.is_ascii_quasi) o symbol);

val scan_alphanumeric = Scan.one (Symbol.is_ascii_letter o symbol) -- scan_letdigs >> op ::;

val scan_symbolic = Scan.many1 (member (op =) (explode "!#$%&*+-/:<=>?@\\^`|~") o symbol);

in

val scan_ident = scan_alphanumeric || scan_symbolic;

val scan_longident =

  (Scan.repeat1 (scan_alphanumeric @@@ $$$ ".") >> flat) @@@ (scan_ident || $$$ "=");

val scan_typevar = $$$ "'" @@@ scan_letdigs;

end;

(* numerals *)

local

val scan_dec = Scan.many1 (Symbol.is_ascii_digit o symbol);

val scan_hex = Scan.many1 (Symbol.is_ascii_hex o symbol);

val scan_sign = Scan.optional ($$$ "~") [];

val scan_decint = scan_sign @@@ scan_dec;

in

val scan_word =

  $$$ "0" @@@ $$$ "w" @@@ $$$ "x" @@@ scan_hex ||

  $$$ "0" @@@ $$$ "w" @@@ scan_dec;

val scan_int = scan_sign @@@ ($$$ "0" @@@ $$$ "x" @@@ scan_hex || scan_dec);

val scan_exp = ($$$ "E" || $$$ "e") @@@ scan_decint;

val scan_real =

  scan_decint @@@ $$$ "." @@@ scan_dec @@@ Scan.optional scan_exp [] ||

  scan_decint @@@ scan_exp;

end;

(* chars and strings *)

local

val scan_escape =

  Scan.one (member (op =) (explode "\"\\abtnvfr") o symbol) >> single ||

  $$$ "^" @@@ (Scan.one (fn (s, _) => ord "@" <= ord s andalso ord s <= ord "_") >> single) ||

  Scan.one (Symbol.is_ascii_digit o symbol) --

    Scan.one (Symbol.is_ascii_digit o symbol) --

    Scan.one (Symbol.is_ascii_digit o symbol) >> (fn ((a, b), c) => [a, b, c]);

val scan_str =

  Scan.one (fn (s, _) => Symbol.is_printable s andalso s <> "\"" andalso s <> "\\") >> single ||

  $$$ "\\" @@@ !!! "bad escape character in string" scan_escape;

val scan_gap = $$$ "\\" @@@ scan_blanks1 @@@ $$$ "\\";

val scan_gaps = Scan.repeat scan_gap >> flat;

in

val scan_char =

  $$$ "#" @@@ $$$ "\"" @@@ scan_gaps @@@ scan_str @@@ scan_gaps @@@ $$$ "\"";

val scan_string =

  $$$ "\"" @@@ !!! "missing quote at end of string"

    ((Scan.repeat (scan_gap || scan_str) >> flat) @@@ $$$ "\"");

end;

(* token source *)

local

fun token k ss = Token (SymbolPos.range ss, (k, SymbolPos.implode ss));

val scan = !!! "bad input"

 (scan_char >> token Char ||

  scan_string >> token String ||

  scan_blanks1 >> token Space ||

  SymbolPos.scan_comment !!! >> token Comment ||

  Scan.max token_leq

   (scan_keyword >> token Keyword)

   (scan_word >> token Word ||

    scan_real >> token Real ||

    scan_int >> token Int ||

    scan_longident >> token LongIdent ||

    scan_ident >> token Ident ||

    scan_typevar >> token TypeVar));

fun recover msg =

  Scan.many (((not o Symbol.is_blank) andf Symbol.is_regular) o symbol)

  >> (fn cs => [token (Error msg) cs]);

in

fun source src =

  SymbolPos.source (Position.line 1) src

  |> Source.source SymbolPos.stopper (Scan.bulk scan) (SOME (false, recover));

end;

end;