defer evaluation of Scan.message, for improved performance in the frequent situation where failure is handled later (e.g. via ||);
1 (* Title: Pure/General/scan.ML
2 Author: Markus Wenzel and Tobias Nipkow, TU Muenchen
4 Generic scanners (for potentially infinite input).
7 infix 5 -- :-- :|-- |-- --| ^^;
12 signature BASIC_SCAN =
14 type message = unit -> string
16 val !! : ('a * message option -> message) -> ('a -> 'b) -> 'a -> 'b
18 val >> : ('a -> 'b * 'c) * ('b -> 'd) -> 'a -> 'd * 'c
20 val || : ('a -> 'b) * ('a -> 'b) -> 'a -> 'b
21 (*sequential pairing*)
22 val -- : ('a -> 'b * 'c) * ('c -> 'd * 'e) -> 'a -> ('b * 'd) * 'e
24 val :-- : ('a -> 'b * 'c) * ('b -> 'c -> 'd * 'e) -> 'a -> ('b * 'd) * 'e
26 val :|-- : ('a -> 'b * 'c) * ('b -> 'c -> 'd * 'e) -> 'a -> 'd * 'e
27 val |-- : ('a -> 'b * 'c) * ('c -> 'd * 'e) -> 'a -> 'd * 'e
28 val --| : ('a -> 'b * 'c) * ('c -> 'd * 'e) -> 'a -> 'b * 'e
30 val ^^ : ('a -> string * 'b) * ('b -> string * 'c) -> 'a -> string * 'c
31 val ::: : ('a -> 'b * 'c) * ('c -> 'b list * 'd) -> 'a -> 'b list * 'd
32 val @@@ : ('a -> 'b list * 'c) * ('c -> 'b list * 'd) -> 'a -> 'b list * 'd
33 (*one element literal*)
34 val $$ : string -> string list -> string * string list
35 val ~$$ : string -> string list -> string * string list
41 val prompt: string -> ('a -> 'b) -> 'a -> 'b
42 val error: ('a -> 'b) -> 'a -> 'b
43 val catch: ('a -> 'b) -> 'a -> 'b (*exception Fail*)
45 val fail_with: ('a -> message) -> 'a -> 'b
46 val succeed: 'a -> 'b -> 'a * 'b
47 val some: ('a -> 'b option) -> 'a list -> 'b * 'a list
48 val one: ('a -> bool) -> 'a list -> 'a * 'a list
49 val this: string list -> string list -> string list * string list
50 val this_string: string -> string list -> string * string list
51 val many: ('a -> bool) -> 'a list -> 'a list * 'a list
52 val many1: ('a -> bool) -> 'a list -> 'a list * 'a list
53 val optional: ('a -> 'b * 'a) -> 'b -> 'a -> 'b * 'a
54 val option: ('a -> 'b * 'a) -> 'a -> 'b option * 'a
55 val repeat: ('a -> 'b * 'a) -> 'a -> 'b list * 'a
56 val repeat1: ('a -> 'b * 'a) -> 'a -> 'b list * 'a
57 val single: ('a -> 'b * 'a) -> 'a -> 'b list * 'a
58 val bulk: ('a -> 'b * 'a) -> 'a -> 'b list * 'a
59 val max: ('a * 'a -> bool) -> ('b -> 'a * 'b) -> ('b -> 'a * 'b) -> 'b -> 'a * 'b
60 val ahead: ('a -> 'b * 'c) -> 'a -> 'b * 'a
61 val unless: ('a -> 'b * 'a) -> ('a -> 'c * 'd) -> 'a -> 'c * 'd
62 val first: ('a -> 'b) list -> 'a -> 'b
63 val state: 'a * 'b -> 'a * ('a * 'b)
64 val depend: ('a -> 'b -> ('c * 'd) * 'e) -> 'a * 'b -> 'd * ('c * 'e)
65 val peek: ('a -> 'b -> 'c * 'd) -> 'a * 'b -> 'c * ('a * 'd)
66 val pass: 'a -> ('a * 'b -> 'c * ('d * 'e)) -> 'b -> 'c * 'e
67 val lift: ('a -> 'b * 'c) -> 'd * 'a -> 'b * ('d * 'c)
68 val unlift: (unit * 'a -> 'b * ('c * 'd)) -> 'a -> 'b * 'd
69 val trace: ('a list -> 'b * 'c list) -> 'a list -> ('b * 'a list) * 'c list
71 val stopper: ('a list -> 'a) -> ('a -> bool) -> 'a stopper
72 val is_stopper: 'a stopper -> 'a -> bool
73 val finite': 'a stopper -> ('b * 'a list -> 'c * ('d * 'a list))
74 -> 'b * 'a list -> 'c * ('d * 'a list)
75 val finite: 'a stopper -> ('a list -> 'b * 'a list) -> 'a list -> 'b * 'a list
76 val read: 'a stopper -> ('a list -> 'b * 'a list) -> 'a list -> 'b option
77 val drain: string -> (string -> 'a -> 'b list * 'a) -> 'b stopper ->
78 ('c * 'b list -> 'd * ('e * 'b list)) -> ('c * 'b list) * 'a -> ('d * ('e * 'b list)) * 'a
80 val is_literal: lexicon -> string list -> bool
81 val literal: lexicon -> (string * 'a) list -> (string * 'a) list * (string * 'a) list
82 val empty_lexicon: lexicon
83 val extend_lexicon: string list -> lexicon -> lexicon
84 val make_lexicon: string list list -> lexicon
85 val dest_lexicon: lexicon -> string list
86 val merge_lexicons: lexicon * lexicon -> lexicon
89 structure Scan: SCAN =
97 type message = unit -> string;
99 exception MORE of string option; (*need more input (prompt)*)
100 exception FAIL of message option; (*try alternatives (reason of failure)*)
101 exception ABORT of message; (*dead end*)
103 fun !! err scan xs = scan xs handle FAIL msg => raise ABORT (err (xs, msg));
104 fun permissive scan xs = scan xs handle MORE _ => raise FAIL NONE | ABORT _ => raise FAIL NONE;
105 fun strict scan xs = scan xs handle MORE _ => raise FAIL NONE;
106 fun prompt str scan xs = scan xs handle MORE NONE => raise MORE (SOME str);
107 fun error scan xs = scan xs handle ABORT msg => Library.error (msg ());
109 fun catch scan xs = scan xs
110 handle ABORT msg => raise Fail (msg ())
111 | FAIL msg => raise Fail (case msg of NONE => "Syntax error" | SOME m => m ());
114 (* scanner combinators *)
116 fun (scan >> f) xs = scan xs |>> f;
118 fun (scan1 || scan2) xs = scan1 xs handle FAIL _ => scan2 xs;
120 fun (scan1 :-- scan2) xs =
122 val (x, ys) = scan1 xs;
123 val (y, zs) = scan2 x ys;
126 fun (scan1 -- scan2) = scan1 :-- (fn _ => scan2);
127 fun (scan1 :|-- scan2) = scan1 :-- scan2 >> #2;
128 fun (scan1 |-- scan2) = scan1 -- scan2 >> #2;
129 fun (scan1 --| scan2) = scan1 -- scan2 >> #1;
130 fun (scan1 ^^ scan2) = scan1 -- scan2 >> op ^;
131 fun (scan1 ::: scan2) = scan1 -- scan2 >> op ::;
132 fun (scan1 @@@ scan2) = scan1 -- scan2 >> op @;
135 (* generic scanners *)
137 fun fail _ = raise FAIL NONE;
138 fun fail_with msg_of xs = raise FAIL (SOME (msg_of xs));
139 fun succeed y xs = (y, xs);
141 fun some _ [] = raise MORE NONE
143 (case f x of SOME y => (y, xs) | _ => raise FAIL NONE);
145 fun one _ [] = raise MORE NONE
146 | one pred (x :: xs) =
147 if pred x then (x, xs) else raise FAIL NONE;
149 fun $$ a = one (fn s: string => s = a);
150 fun ~$$ a = one (fn s: string => s <> a);
154 fun drop_prefix [] xs = xs
155 | drop_prefix (_ :: _) [] = raise MORE NONE
156 | drop_prefix (y :: ys) (x :: xs) =
157 if (y: string) = x then drop_prefix ys xs else raise FAIL NONE;
158 in (ys, drop_prefix ys xs) end;
160 fun this_string s = this (raw_explode s) >> K s; (*primitive string -- no symbols here!*)
162 fun many _ [] = raise MORE NONE
163 | many pred (lst as x :: xs) =
164 if pred x then apfst (cons x) (many pred xs)
167 fun many1 pred = one pred ::: many pred;
169 fun optional scan def = scan || succeed def;
170 fun option scan = (scan >> SOME) || succeed NONE;
175 (case (SOME (scan xs) handle FAIL _ => NONE) of
177 | SOME (y, xs') => rep (y :: ys) xs');
180 fun repeat1 scan = scan ::: repeat scan;
182 fun single scan = scan >> (fn x => [x]);
183 fun bulk scan = scan -- repeat (permissive scan) >> (op ::);
185 fun max leq scan1 scan2 xs =
186 (case (option scan1 xs, option scan2 xs) of
187 ((NONE, _), (NONE, _)) => raise FAIL NONE (*looses FAIL msg!*)
188 | ((SOME tok1, xs'), (NONE, _)) => (tok1, xs')
189 | ((NONE, _), (SOME tok2, xs')) => (tok2, xs')
190 | ((SOME tok1, xs1'), (SOME tok2, xs2')) =>
191 if leq (tok2, tok1) then (tok1, xs1') else (tok2, xs2'));
193 fun ahead scan xs = (fst (scan xs), xs);
195 fun unless test scan =
196 ahead (option test) :-- (fn NONE => scan | _ => fail) >> #2;
199 | first (scan :: scans) = scan || first scans;
202 (* state based scanners *)
204 fun state (st, xs) = (st, (st, xs));
206 fun depend scan (st, xs) =
207 let val ((st', y), xs') = scan st xs
208 in (y, (st', xs')) end;
210 fun peek scan = depend (fn st => scan st >> pair st);
212 fun pass st scan xs =
213 let val (y, (_, xs')) = scan (st, xs)
216 fun lift scan (st, xs) =
217 let val (y, xs') = scan xs
218 in (y, (st, xs')) end;
220 fun unlift scan = pass () scan;
226 let val (y, xs') = scan xs
227 in ((y, take (length xs - length xs') xs), xs') end;
232 datatype 'a stopper = Stopper of ('a list -> 'a) * ('a -> bool);
234 fun stopper mk_stopper is_stopper = Stopper (mk_stopper, is_stopper);
235 fun is_stopper (Stopper (_, is_stopper)) = is_stopper;
240 fun finite' (Stopper (mk_stopper, is_stopper)) scan (state, input) =
242 fun lost () = raise ABORT (fn () => "Bad scanner: lost stopper of finite scan!");
244 fun stop [] = lost ()
246 let val (xs, x) = split_last lst
247 in if is_stopper x then ((), xs) else lost () end;
249 if exists is_stopper input then
250 raise ABORT (fn () => "Stopper may not occur in input of finite scan!")
251 else (strict scan --| lift stop) (state, input @ [mk_stopper input])
254 fun finite stopper scan = unlift (finite' stopper (lift scan));
256 fun read stopper scan xs =
257 (case error (finite stopper (option scan)) xs of
258 (y as SOME _, []) => y
262 (* infinite scans -- draining state-based source *)
264 fun drain def_prompt get stopper scan ((state, xs), src) =
265 (scan (state, xs), src) handle MORE prompt =>
266 (case get (the_default def_prompt prompt) src of
267 ([], _) => (finite' stopper scan (state, xs), src)
268 | (xs', src') => drain def_prompt get stopper scan ((state, xs @ xs'), src'));
272 (** datatype lexicon -- position tree **)
274 datatype lexicon = Lexicon of (bool * lexicon) Symtab.table;
276 val empty_lexicon = Lexicon Symtab.empty;
278 fun is_literal _ [] = false
279 | is_literal (Lexicon tab) (c :: cs) =
280 (case Symtab.lookup tab c of
281 SOME (tip, lex) => tip andalso null cs orelse is_literal lex cs
285 (* scan longest match *)
287 fun literal lexicon =
289 fun finish (SOME (res, rest)) = (rev res, rest)
290 | finish NONE = raise FAIL NONE;
291 fun scan _ res (Lexicon tab) [] = if Symtab.is_empty tab then finish res else raise MORE NONE
292 | scan path res (Lexicon tab) (c :: cs) =
293 (case Symtab.lookup tab (fst c) of
295 let val path' = c :: path
296 in scan path' (if tip then SOME (path', cs) else res) lex cs end
297 | NONE => finish res);
298 in scan [] NONE lexicon end;
303 fun extend_lexicon chrs lexicon =
306 | ext (c :: cs) (Lexicon tab) =
307 (case Symtab.lookup tab c of
308 SOME (tip, lex) => Lexicon (Symtab.update (c, (tip orelse null cs, ext cs lex)) tab)
309 | NONE => Lexicon (Symtab.update (c, (null cs, ext cs empty_lexicon)) tab));
310 in if is_literal lexicon chrs then lexicon else ext chrs lexicon end;
312 fun make_lexicon chrss = fold extend_lexicon chrss empty_lexicon;
317 fun dest path (Lexicon tab) = Symtab.fold (fn (d, (tip, lex)) =>
319 val path' = d :: path;
320 val content = dest path' lex;
321 in append (if tip then rev path' :: content else content) end) tab [];
323 val dest_lexicon = map implode o dest [];
324 fun merge_lexicons (lex1, lex2) = fold extend_lexicon (dest [] lex2) lex1;
328 structure Basic_Scan: BASIC_SCAN = Scan;