src/Pure/Thy/rail.ML

more standard parser combinator expressions and tool setup;

(*  Title:      Pure/Thy/rail.ML
    Author:     Michael Kerscher, TU München
    Author:     Makarius

Railroad diagrams in LaTeX.
*)

structure Rail: sig end =
struct

(** lexical syntax **)

(* datatype token *)

datatype kind =
  Keyword | Ident | String | Antiq of Symbol_Pos.T list * Position.range | EOF;

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

fun pos_of (Token ((pos, _), _)) = pos;
fun end_pos_of (Token ((_, pos), _)) = pos;

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


(* diagnostics *)

val print_kind =
 fn Keyword => "rail keyword"
  | Ident => "identifier"
  | String => "single-quoted string"
  | Antiq _ => "antiquotation"
  | EOF => "end-of-input";

fun print (Token ((pos, _), (k, x))) =
  (if k = EOF then print_kind k else print_kind k ^ " " ^ quote x) ^
  Position.here pos;

fun print_keyword x = print_kind Keyword ^ " " ^ quote x;


(* stopper *)

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_pos_of (List.last toks))) is_eof;


(* tokenize *)

local

fun token k ss = [Token (Symbol_Pos.range ss, (k, Symbol_Pos.content ss))];

val scan_space = Scan.many1 (Symbol.is_blank o Symbol_Pos.symbol);

val scan_keyword =
  Scan.one (member (op =) ["|", "*", "+", "?", "(", ")", "\\", ";", ":", "@"] o Symbol_Pos.symbol);

val err_prefix = "Rail lexical error: ";

val scan_token =
  scan_space >> K [] ||
  Antiquote.scan_antiq >> (fn antiq as (ss, _) => token (Antiq antiq) ss) ||
  scan_keyword >> (token Keyword o single) ||
  Lexicon.scan_id >> token Ident ||
  Symbol_Pos.scan_string_q err_prefix >> (token String o #1 o #2);

val scan =
  (Scan.repeat scan_token >> flat) --|
    Symbol_Pos.!!! (fn () => err_prefix ^ "bad input")
      (Scan.ahead (Scan.one Symbol_Pos.is_eof));

in

val tokenize = #1 o Scan.error (Scan.finite Symbol_Pos.stopper scan) o Symbol_Pos.explode;

end;



(** parsing **)

fun !!! scan =
  let
    val prefix = "Rail syntax error";

    fun get_pos [] = " (end-of-input)"
      | get_pos (tok :: _) = Position.here (pos_of tok);

    fun err (toks, NONE) = (fn () => prefix ^ get_pos toks)
      | err (toks, SOME msg) =
          (fn () =>
            let val s = msg () in
              if String.isPrefix prefix s then s
              else prefix ^ get_pos toks ^ ": " ^ s
            end);
  in Scan.!! err scan end;

fun $$$ x =
  Scan.one (fn tok => kind_of tok = Keyword andalso content_of tok = x) ||
  Scan.fail_with
    (fn [] => (fn () => print_keyword x ^ " expected,\nbut end-of-input was found")
      | tok :: _ => (fn () => print_keyword x ^ " expected,\nbut " ^ print tok ^ " was found"));

fun enum1 sep scan = scan ::: Scan.repeat ($$$ sep |-- !!! scan);
fun enum sep scan = enum1 sep scan || Scan.succeed [];

val ident = Scan.some (fn tok => if kind_of tok = Ident then SOME (content_of tok) else NONE);
val string = Scan.some (fn tok => if kind_of tok = String then SOME (content_of tok) else NONE);

val antiq = Scan.some (fn tok => (case kind_of tok of Antiq a => SOME a | _ => NONE));



(** rail expressions **)

(* datatype *)

datatype rails =
  Cat of int * rail list
and rail =
  Bar of rails list |
  Plus of rails * rails |
  Newline of int |
  Nonterminal of string |
  Terminal of bool * string |
  Antiquote of bool * (Symbol_Pos.T list * Position.range);

fun reverse_cat (Cat (y, rails)) = Cat (y, rev (map reverse rails))
and reverse (Bar cats) = Bar (map reverse_cat cats)
  | reverse (Plus (cat1, cat2)) = Plus (reverse_cat cat1, reverse_cat cat2)
  | reverse x = x;

fun cat rails = Cat (0, rails);

val empty = cat [];
fun is_empty (Cat (_, [])) = true | is_empty _ = false;

fun is_newline (Newline _) = true | is_newline _ = false;

fun bar [Cat (_, [rail])] = rail
  | bar cats = Bar cats;

fun plus cat1 cat2 = Plus (cat1, reverse_cat cat2);

fun star cat1 cat2 =
  if is_empty cat2 then plus empty cat1
  else bar [empty, cat [plus cat1 cat2]];

fun maybe rail = bar [empty, cat [rail]];


(* read *)

local

val at_mode = Scan.option ($$$ "@") >> (fn NONE => false | _ => true);

fun body x = (enum1 "|" body1 >> bar) x
and body0 x = (enum "|" body1 >> bar) x
and body1 x =
 (body2 :|-- (fn a =>
   $$$ "*" |-- !!! body4e >> (cat o single o star a) ||
   $$$ "+" |-- !!! body4e >> (cat o single o plus a) ||
   Scan.succeed a)) x
and body2 x = (Scan.repeat1 body3 >> cat) x
and body3 x = (body4 :|-- (fn a => $$$ "?" >> K (maybe a) || Scan.succeed a)) x
and body4 x =
 ($$$ "(" |-- !!! (body0 --| $$$ ")") ||
  $$$ "\\" >> K (Newline 0) ||
  ident >> Nonterminal ||
  at_mode -- string >> Terminal ||
  at_mode -- antiq >> Antiquote) x
and body4e x = (Scan.option body4 >> (cat o the_list)) x;

val rule_name = ident >> Antiquote.Text || antiq >> Antiquote.Antiq;
val rule = rule_name -- ($$$ ":" |-- !!! body) || body >> pair (Antiquote.Text "");
val rules = enum1 ";" (Scan.option rule) >> map_filter I;

in

val read =
  #1 o Scan.error (Scan.finite stopper (rules --| !!! (Scan.ahead (Scan.one is_eof)))) o tokenize;

end;


(* latex output *)

local

fun vertical_range_cat (Cat (_, rails)) y =
  let val (rails', (_, y')) =
    fold_map (fn rail => fn (y0, y') =>
      if is_newline rail then (Newline (y' + 1), (y' + 1, y' + 2))
      else
        let val (rail', y0') = vertical_range rail y0;
        in (rail', (y0, Int.max (y0', y'))) end) rails (y, y + 1)
  in (Cat (y, rails'), y') end

and vertical_range (Bar cats) y =
      let val (cats', y') = fold_map vertical_range_cat cats y
      in (Bar cats', Int.max (y + 1, y')) end
  | vertical_range (Plus (cat1, cat2)) y =
      let val ([cat1', cat2'], y') = fold_map vertical_range_cat [cat1, cat2] y;
      in (Plus (cat1', cat2'), Int.max (y + 1, y')) end
  | vertical_range (Newline _) y = (Newline (y + 2), y + 3)
  | vertical_range atom y = (atom, y + 1);

fun output_rules state rules =
  let
    val output_antiq = Thy_Output.eval_antiq (#1 (Keyword.get_lexicons ())) state;
    fun output_text b s =
      Output.output s
      |> b ? enclose "\\isakeyword{" "}"
      |> enclose "\\isa{" "}";

    fun output_cat c (Cat (_, rails)) = outputs c rails
    and outputs c [rail] = output c rail
      | outputs _ rails = implode (map (output "") rails)
    and output _ (Bar []) = ""
      | output c (Bar [cat]) = output_cat c cat
      | output _ (Bar (cat :: cats)) =
          "\\rail@bar\n" ^ output_cat "" cat ^
          implode (map (fn Cat (y, rails) =>
              "\\rail@nextbar{" ^ string_of_int y ^ "}\n" ^ outputs "" rails) cats) ^
          "\\rail@endbar\n"
      | output c (Plus (cat, Cat (y, rails))) =
          "\\rail@plus\n" ^ output_cat c cat ^
          "\\rail@nextplus{" ^ string_of_int y ^ "}\n" ^ outputs "c" rails ^
          "\\rail@endplus\n"
      | output _ (Newline y) = "\\rail@cr{" ^ string_of_int y ^ "}\n"
      | output c (Nonterminal s) = "\\rail@" ^ c ^ "nont{" ^ output_text false s ^ "}[]\n"
      | output c (Terminal (b, s)) = "\\rail@" ^ c ^ "term{" ^ output_text b s ^ "}[]\n"
      | output c (Antiquote (b, a)) =
          "\\rail@" ^ c ^ (if b then "term{" else "nont{") ^ output_antiq a ^ "}[]\n";

    fun output_rule (name, rail) =
      let
        val (rail', y') = vertical_range rail 0;
        val out_name =
          (case name of
            Antiquote.Text "" => ""
          | Antiquote.Text s => output_text false s
          | Antiquote.Antiq a => output_antiq a);
      in
        "\\rail@begin{" ^ string_of_int y' ^ "}{" ^ out_name ^ "}\n" ^
        output "" rail' ^
        "\\rail@end\n"
      end;
  in
    "\\begin{railoutput}\n" ^
    implode (map output_rule rules) ^
    "\\end{railoutput}\n"
  end;

in

val _ = Theory.setup
  (Thy_Output.antiquotation (Binding.name "rail")
    (Scan.lift (Parse.source_position Parse.string))
    (fn {state, ...} => output_rules state o read));

end;

end;