(*  Title:      Pure/General/symbol_pos.ML

     ID:         $Id$

     Author:     Makarius

 Symbols with explicit position information.

 *)

 signature BASIC_SYMBOL_POS =

 sig

   type T = Symbol.symbol * Position.T

   val symbol: T -> Symbol.symbol

   val $$$ : Symbol.symbol -> T list -> T list * T list

   val ~$$$ : Symbol.symbol -> T list -> T list * T list

 end

 signature SYMBOL_POS =

 sig

   include BASIC_SYMBOL_POS

   val is_eof: T -> bool

   val stopper: T Scan.stopper

   val !!! : string -> (T list -> 'a) -> T list -> 'a

   val scan_pos: T list -> Position.T * T list

   val scan_comment: (string -> (T list -> T list * T list) -> T list -> T list * T list) ->

     T list -> T list * T list

   val scan_comment_body: (string -> (T list -> T list * T list) -> T list -> T list * T list) ->

     T list -> T list * T list

   val source: Position.T -> (Symbol.symbol, 'a) Source.source ->

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

   type text = string

   val implode: T list -> text * Position.range

   val implode_delim: Position.T -> Position.T -> T list -> text * Position.range

   val explode: text * Position.T -> T list

 end;

 structure SymbolPos: SYMBOL_POS =

 struct

 (* type T *)

 type T = Symbol.symbol * Position.T;

 fun symbol ((s, _): T) = s;

 (* stopper *)

 fun mk_eof pos = (Symbol.eof, pos);

 val eof = mk_eof Position.none;

 val is_eof = Symbol.is_eof o symbol;

 val stopper =

   Scan.stopper (fn [] => eof | inp => mk_eof (List.last inp |-> Position.advance)) is_eof;

 (* basic scanners *)

 fun !!! text scan =

   let

     fun get_pos [] = " (past end-of-text!)"

       | get_pos ((_, pos) :: _) = Position.str_of pos;

     fun err (syms, msg) =

       text ^ get_pos syms ^ " at " ^ Symbol.beginning 10 (map symbol syms) ^

       (case msg of NONE => "" | SOME s => "\n" ^ s);

   in Scan.!! err scan end;

 fun $$$ s = Scan.one (fn x => symbol x = s) >> single;

 fun ~$$$ s = Scan.one (fn x => symbol x <> s) >> single;

 val scan_pos = Scan.ahead (Scan.one (K true)) >> (fn (_, pos): T => pos);

 (* ML-style comments *)

 local

 val scan_cmt =

   Scan.depend (fn (d: int) => $$$ "(" @@@ $$$ "*" >> pair (d + 1)) ||

   Scan.depend (fn 0 => Scan.fail | d => $$$ "*" @@@ $$$ ")" >> pair (d - 1)) ||

   Scan.lift ($$$ "*" --| Scan.ahead (~$$$ ")")) ||

   Scan.lift (Scan.one (fn (s, _) => s <> "*" andalso Symbol.is_regular s)) >> single;

 val scan_body = Scan.pass 0 (Scan.repeat scan_cmt >> flat);

 in

 fun scan_comment cut =

   $$$ "(" @@@ $$$ "*" @@@ cut "missing end of comment" (scan_body @@@ $$$ "*" @@@ $$$ ")");

 fun scan_comment_body cut =

   $$$ "(" |-- $$$ "*" |-- cut "missing end of comment" (scan_body --| $$$ "*" --| $$$ ")");

 end;

 (* source *)

 fun source pos =

   Source.source' pos Symbol.stopper (Scan.bulk (Scan.depend (fn pos =>

     Scan.one Symbol.not_eof >> (fn s => (Position.advance s pos, (s, pos)))))) NONE;

 (* compact representation -- with Symbol.DEL padding *)

 type text = string;

 local

 fun pad [] = []

   | pad [(s, _)] = [s]

   | pad ((s1, pos1) :: (rest as (s2, pos2) :: _)) =

       let

         fun err () =

           raise Fail ("Misaligned symbols: " ^

             quote s1 ^ Position.str_of pos1 ^ " " ^

             quote s2 ^ Position.str_of pos2);

         val end_pos1 = Position.advance s1 pos1;

         val _ = Position.line_of end_pos1 = Position.line_of pos2 orelse err ();

         val d =

           (case (Position.column_of end_pos1, Position.column_of pos2) of

             (NONE, NONE) => 0

           | (SOME n1, SOME n2) => n2 - n1

           | _ => err ());

         val _ = d >= 0 orelse err ();

       in s1 :: replicate d Symbol.DEL @ pad rest end;

 val orig_implode = implode;

 in

 fun implode (syms as (_, pos) :: _) =

       let val pos' = List.last syms |-> Position.advance

       in (orig_implode (pad syms), Position.range pos pos') end

   | implode [] = ("", (Position.none, Position.none));

 fun implode_delim pos1 pos2 syms = implode (("", pos1) :: syms @ [("", pos2)]);

 fun explode (str, pos) =

   fold_map (fn s => fn p => ((s, p), (Position.advance s p)))

     (Symbol.explode str) (Position.reset_range pos)

   |> #1 |> filter_out (fn (s, _) => s = Symbol.DEL);

 end;

 end;

 structure BasicSymbolPos: BASIC_SYMBOL_POS = SymbolPos;   (*not open by default*)