# HG changeset patch
# User wenzelm
# Date 889456339 -3600
# Node ID ffbaf431665d33c4d4d35d3f3355547bde2c60c5
# Parent  be8a8d60d9628cfc39cfac737ce6849c06cce6f1
Generic scanners (for potentially infinite input) -- replaces Scanner;

diff -r be8a8d60d962 -r ffbaf431665d src/Pure/Syntax/scan.ML
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/Pure/Syntax/scan.ML	Mon Mar 09 16:12:19 1998 +0100
@@ -0,0 +1,259 @@
+(*  Title:	Pure/Syntax/scan.ML
+    ID:		$Id$
+    Author:	Markus Wenzel and Tobias Nipkow, TU Muenchen
+
+Generic scanners (for potentially infinite input).
+*)
+
+infix 5 -- |-- --| ^^;
+infix 3 >>;
+infix 0 ||;
+
+signature BASIC_SCAN =
+sig
+  val !! : ('a -> string) -> ('a -> 'b) -> 'a -> 'b
+  val >> : ('a -> 'b * 'c) * ('b -> 'd) -> 'a -> 'd * 'c
+  val || : ('a -> 'b) * ('a -> 'b) -> 'a -> 'b
+  val -- : ('a -> 'b * 'c) * ('c -> 'd * 'e) -> 'a -> ('b * 'd) * 'e
+  val |-- : ('a -> 'b * 'c) * ('c -> 'd * 'e) -> 'a -> 'd * 'e
+  val --| : ('a -> 'b * 'c) * ('c -> 'd * 'e) -> 'a -> 'b * 'e
+  val ^^ : ('a -> string * 'b) * ('b -> string * 'c) -> 'a -> string * 'c
+  val $$ : ''a -> ''a list -> ''a * ''a list
+end;
+
+signature SCAN =
+sig
+  include BASIC_SCAN
+  val fail: 'a -> 'b
+  val succeed: 'a -> 'b -> 'a * 'b
+  val one: ('a -> bool) -> 'a list -> 'a * 'a list
+  val any: ('a -> bool) -> 'a list -> 'a list * 'a list
+  val any1: ('a -> bool) -> 'a list -> 'a list * 'a list
+  val optional: ('a -> 'b * 'a) -> 'b -> 'a -> 'b * 'a
+  val option: ('a -> 'b * 'a) -> 'a -> 'b option * 'a
+  val repeat: ('a -> 'b * 'a) -> 'a -> 'b list * 'a
+  val repeat1: ('a -> 'b * 'a) -> 'a -> 'b list * 'a
+  val max: ('a * 'a -> bool) -> ('b -> 'a * 'b) -> ('b -> 'a * 'b) -> 'b -> 'a * 'b
+  val ahead: ('a -> 'b * 'c) -> 'a -> 'b * 'a
+  val depend: ('a -> 'b -> ('c * 'd) * 'e) -> 'a * 'b -> 'd * ('c * 'e)
+  val lift: ('a -> 'b * 'c) -> 'd * 'a -> 'b * ('d * 'c)
+  val pass: 'a -> ('a * 'b -> 'c * ('d * 'e)) -> 'b -> 'c * 'e
+  val force: ('a -> 'b) -> 'a -> 'b
+  val finite': ''a -> ('b * ''a list -> 'c * ('d * ''a list))
+    -> 'b * ''a list -> 'c * ('d * ''a list)
+  val finite: ''a -> (''a list -> 'b * ''a list) -> ''a list -> 'b * ''a list
+  val error: ('a -> 'b) -> 'a -> 'b
+  val source: ('a -> 'b list * 'a) -> ('b list * 'a -> 'c)
+    -> ('b list -> 'd * 'b list) -> 'a -> 'd list * 'c
+  type lexicon
+  val dest_lexicon: lexicon -> string list list
+  val make_lexicon: string list list -> lexicon
+  val empty_lexicon: lexicon
+  val extend_lexicon: lexicon -> string list list -> lexicon
+  val merge_lexicons: lexicon -> lexicon -> lexicon
+  val literal: lexicon -> string list -> string list * string list
+end;
+
+structure Scan: SCAN =
+struct
+
+
+(** scanners **)
+
+exception MORE;			(*need more input*)
+exception FAIL;			(*try alternatives*)
+exception ABORT of string;	(*dead end*)
+
+
+(* scanner combinators *)
+
+fun (scan >> f) xs = apfst f (scan xs);
+
+fun (scan1 || scan2) xs = scan1 xs handle FAIL => scan2 xs;
+
+fun (scan1 -- scan2) xs =
+  let
+    val (x, ys) = scan1 xs;
+    val (y, zs) = scan2 ys;
+  in ((x, y), zs) end;
+
+fun (scan1 |-- scan2) = scan1 -- scan2 >> #2;
+fun (scan1 --| scan2) = scan1 -- scan2 >> #1;
+
+fun (scan1 ^^ scan2) = scan1 -- scan2 >> op ^;
+
+
+(* generic scanners *)
+
+fun fail _ = raise FAIL;
+fun succeed y xs = (y, xs);
+
+fun one _ [] = raise MORE
+  | one pred (x :: xs) =
+      if pred x then (x, xs) else raise FAIL;
+
+fun $$ _ [] = raise MORE
+  | $$ a (x :: xs) =
+      if a = x then (x, xs) else raise FAIL;
+
+fun any _ [] = raise MORE
+  | any pred (lst as x :: xs) =
+      if pred x then apfst (cons x) (any pred xs)
+      else ([], lst);
+
+fun any1 pred = one pred -- any pred >> op ::;
+
+fun optional scan def = scan || succeed def;
+fun option scan = optional (scan >> Some) None;
+
+fun repeat scan xs = (scan -- repeat scan >> op :: || succeed []) xs;
+fun repeat1 scan = scan -- repeat scan >> op ::;
+
+fun max leq scan1 scan2 xs =
+  (case (option scan1 xs, option scan2 xs) of
+    ((None, _), (None, _)) => raise FAIL
+  | ((Some tok1, xs'), (None, _)) => (tok1, xs')
+  | ((None, _), (Some tok2, xs')) => (tok2, xs')
+  | ((Some tok1, xs1'), (Some tok2, xs2')) =>
+      if leq (tok2, tok1) then (tok1, xs1') else (tok2, xs2'));
+
+fun ahead scan xs = (fst (scan xs), xs);
+
+
+(* state based scanners *)
+
+fun depend scan (st, xs) =
+  let val ((st', y), xs') = scan st xs
+  in (y, (st', xs')) end;
+
+fun lift scan (st, xs) =
+  let val (y, xs') = scan xs
+  in (y, (st, xs')) end;
+
+fun pass st scan xs =
+  let val (y, (_, xs')) = scan (st, xs)
+  in (y, xs') end;
+
+
+(* exception handling *)
+
+fun !! err scan xs = scan xs handle FAIL => raise ABORT (err xs);
+fun force scan xs = scan xs handle MORE => raise FAIL;
+fun error scan xs = scan xs handle ABORT msg => Library.error msg;
+
+
+(* finite scans *)
+
+fun finite' stopper scan (state, input) =
+  let
+    fun lost () = raise ABORT "Scanner bug: lost stopper of finite scan!";
+
+    fun stop [] = lost ()
+      | stop lst =
+          let val (xs, x) = split_last lst
+          in if x = stopper then ((), xs) else lost () end;
+  in
+    if exists (equal stopper) input then
+      raise ABORT "Stopper may not occur in input of finite scan!"
+    else (force scan --| lift stop) (state, input @ [stopper])
+  end;
+
+fun finite stopper scan xs =
+  let val (y, ((), xs')) = finite' stopper (lift scan) ((), xs)
+  in (y, xs') end;
+
+
+(* infinite scans *)		(* FIXME state based!? *)
+
+fun source get unget scan src =
+  let
+    fun try_more x =
+      scan x handle MORE => raise FAIL | ABORT _ => raise FAIL;
+
+    fun drain (xs, s) =
+      (((scan -- repeat try_more) >> op ::) xs, s)
+        handle MORE =>
+          let val (more_xs, s') = get s in
+            if null more_xs then raise ABORT "Input source exhausted"
+            else drain (xs @ more_xs, s')
+          end;
+
+    val ((ys, xs'), src') = drain (get src);
+  in (ys, unget (xs', src')) end;
+
+
+
+
+(** datatype lexicon **)
+
+datatype lexicon =
+  Empty |
+  Branch of string * string list * lexicon * lexicon * lexicon;
+
+val no_literal = [];
+
+
+(* dest_lexicon *)
+
+fun dest_lexicon Empty = []
+  | dest_lexicon (Branch (_, [], lt, eq, gt)) =
+      dest_lexicon lt @ dest_lexicon eq @ dest_lexicon gt
+  | dest_lexicon (Branch (_, cs, lt, eq, gt)) =
+      dest_lexicon lt @ [cs] @ dest_lexicon eq @ dest_lexicon gt;
+
+
+(* empty, extend, make, merge lexicons *)
+
+val empty_lexicon = Empty;
+
+fun extend_lexicon lexicon chrss =
+  let
+    fun ext (lex, chrs) =
+      let
+	fun add (Branch (d, a, lt, eq, gt)) (chs as c :: cs) =
+	      if c < d then Branch (d, a, add lt chs, eq, gt)
+	      else if c > d then Branch (d, a, lt, eq, add gt chs)
+	      else Branch (d, if null cs then chrs else a, lt, add eq cs, gt)
+	  | add Empty [c] =
+	      Branch (c, chrs, Empty, Empty, Empty)
+	  | add Empty (c :: cs) =
+	      Branch (c, no_literal, Empty, add Empty cs, Empty)
+	  | add lex [] = lex;
+      in add lex chrs end;
+  in foldl ext (lexicon, chrss \\ dest_lexicon lexicon) end;
+
+val make_lexicon = extend_lexicon empty_lexicon;
+
+fun merge_lexicons lex1 lex2 =
+  let
+    val chss1 = dest_lexicon lex1;
+    val chss2 = dest_lexicon lex2;
+  in
+    if chss2 subset chss1 then lex1
+    else if chss1 subset chss2 then lex2
+    else extend_lexicon lex1 chss2
+  end;
+
+
+(* scan literal *)
+
+fun literal lex chrs =
+  let
+    fun lit Empty res _ = res
+      | lit (Branch _) _ [] = raise MORE
+      | lit (Branch (d, a, lt, eq, gt)) res (chs as c :: cs) =
+	  if c < d then lit lt res chs
+	  else if c > d then lit gt res chs
+	  else lit eq (if a = no_literal then res else Some (a, cs)) cs;
+  in
+    (case lit lex None chrs of
+      None => raise FAIL
+    | Some res => res)
+  end;
+
+
+end;
+
+
+structure BasicScan: BASIC_SCAN = Scan;
+open BasicScan;