(*  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 content: T list -> string

  val untabify_content: T list -> string

  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

  val range: T list -> Position.range

  val implode_range: 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;

(* content *)

val content = implode o map symbol;

val tab_width = (8: int);

fun untabify ("\t", pos) =

      (case Position.column_of pos of

        SOME n => Symbol.spaces (tab_width - ((n - 1) mod tab_width))

      | NONE => error "No column information -- cannot interpret tabulators")

  | untabify (s, _) = s;

val untabify_content = implode o map untabify;

(* 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;

fun pad [] = []

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

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

      let

        val end_pos1 = Position.advance s1 pos1;

        val d = Int.max (0, Position.distance_of end_pos1 pos2);

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

val implode = implode o pad;

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

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

      in Position.range pos pos' end

  | range [] = Position.no_range;

fun implode_range pos1 pos2 syms =

  let val syms' = (("", pos1) :: syms @ [("", pos2)])

  in (implode syms', range syms') end;

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;

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