src/Pure/ML/ml_lex.ML

filtering out some package theorems

(*  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 * (token -> bool)
  val is_regular: token -> bool
  val is_improper: token -> bool
  val pos_of: token -> string
  val kind_of: token -> token_kind
  val val_of: token -> string
  val keywords: string list
  val source: (Symbol.symbol, 'a) Source.source ->
    (token, int * (Symbol.symbol, 'a) 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 int * (token_kind * string);


(* control tokens *)

val eof = Token (0, (EOF, ""));

fun is_eof (Token (_, (EOF, _))) = true
  | is_eof _ = false;

val stopper = (eof, is_eof);


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;


(* token content *)

fun pos_of (Token (n, _)) = " (line " ^ string_of_int n ^ ")";

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

fun token_leq (Token (_, (_, x)), Token (_, (_, x'))) = x <= x';



(** scanners **)

(* diagnostics *)

fun lex_err msg ((n, cs), _) = "SML lexical error (line " ^ string_of_int n ^ "): " ^ msg cs;
fun !!! msg scan = Scan.!! (lex_err (K msg)) scan;


(* line numbering *)

fun incr_line scan = Scan.depend (fn (n: int) => scan >> pair (n + 1));
val keep_line = Scan.lift;

val scan_blank =
  incr_line ($$ "\n") ||
  keep_line (Scan.one Symbol.is_ascii_blank);

val scan_blanks = Scan.repeat scan_blank >> implode;
val scan_blanks1 = Scan.repeat1 scan_blank >> implode;


(* 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 scan_keyword = Scan.literal (Scan.make_lexicon (map explode keywords)) >> implode;


(* identifiers *)

local

val scan_letdigs =
  Scan.many (Symbol.is_ascii_letter orf Symbol.is_ascii_digit orf Symbol.is_ascii_quasi) >> implode;

val scan_alphanumeric = Scan.one Symbol.is_ascii_letter ^^ scan_letdigs;

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

in

val scan_ident = scan_alphanumeric || scan_symbolic;

val scan_longident =
  (Scan.repeat1 (scan_alphanumeric ^^ $$ ".") >> implode) ^^ (scan_ident || $$ "=");

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

end;


(* numerals *)

local

val scan_dec = Scan.many1 Symbol.is_ascii_digit >> implode;
val scan_hex = Scan.many1 Symbol.is_ascii_hex >> implode;
val scan_sign = Scan.optional ($$ "~") "";
val scan_decint = scan_sign ^^ scan_dec;

in

val scan_word = Scan.this_string "0wx" ^^ scan_hex || Scan.this_string "0w" ^^ scan_dec;

val scan_int = scan_sign ^^ (Scan.this_string "0x" ^^ 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")) ||
  $$ "^" ^^ Scan.one (fn s => ord "@" <= ord s andalso ord s <= ord "_") ||
  Scan.one Symbol.is_ascii_digit ^^
    Scan.one Symbol.is_ascii_digit ^^
    Scan.one Symbol.is_ascii_digit;

val scan_str =
  keep_line (Scan.one (fn s => Symbol.is_printable s andalso s <> "\"" andalso s <> "\\")) ||
  keep_line ($$ "\\") ^^ !!! "bad escape character in string" (keep_line scan_escape);

val scan_gap = keep_line ($$ "\\") ^^ scan_blanks1 ^^ keep_line ($$ "\\");
val scan_gaps = Scan.repeat scan_gap >> implode;

in

val scan_char =
  keep_line ($$ "#" ^^ $$ "\"") ^^ scan_gaps ^^ scan_str ^^ scan_gaps ^^ keep_line ($$ "\"");

val scan_string =
  keep_line ($$ "\"") ^^
  !!! "missing quote at end of string"
    ((Scan.repeat (scan_gap || scan_str) >> implode) ^^ keep_line ($$ "\""));

end;


(* scan nested comments *)

local

val scan_cmt =
  Scan.lift scan_blank ||
  Scan.depend (fn (d: int) => keep_line ($$ "(" ^^ $$ "*") >> pair (d + 1)) ||
  Scan.depend (fn 0 => Scan.fail | d => keep_line ($$ "*" ^^ $$ ")") >> pair (d - 1)) ||
  Scan.lift (keep_line ($$ "*" --| Scan.ahead (~$$ ")"))) ||
  Scan.lift (keep_line (Scan.one (fn s => s <> "*" andalso Symbol.is_regular s)));

in

val scan_comment =
  keep_line ($$ "(" ^^ $$ "*") ^^
  !!! "missing end of comment"
    (Scan.pass 0 (Scan.repeat scan_cmt >> implode) ^^ keep_line ($$ "*" ^^ $$ ")"));

end;


(* scan token *)

val scan =
  let
    val scanner = Scan.state :|-- (fn n =>
      let
        fun token k x = Token (n, (k, x));
      in
        scan_char >> token Char ||
        scan_string >> token String ||
        scan_blanks1 >> token Space ||
        scan_comment >> token Comment ||
        keep_line (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))
      end);
  in !! (lex_err (fn cs => "bad input " ^ quote (Symbol.beginning 10 cs))) scanner end;


(* token source *)

local

val is_junk = (not o Symbol.is_blank) andf Symbol.is_regular;

fun recover msg = Scan.state :|-- (fn n =>
  keep_line (Scan.many is_junk) >> (fn cs => [Token (n, (Error msg, implode cs))]));

in

fun source src =
  Source.source' 1 Symbol.stopper (Scan.bulk scan) (SOME (false, recover)) src;

end;

end;