1 (* ========================================================================= *)
2 (* Inductive (or free recursive) types. *)
4 (* John Harrison, University of Cambridge Computer Laboratory *)
6 (* (c) Copyright, University of Cambridge 1998 *)
7 (* (c) Copyright, John Harrison 1998-2007 *)
8 (* ========================================================================= *)
12 (* ------------------------------------------------------------------------- *)
13 (* Abstract left inverses for binary injections (we could construct them...) *)
14 (* ------------------------------------------------------------------------- *)
16 let INJ_INVERSE2 = prove
18 (!x1 y1 x2 y2. (P x1 y1 = P x2 y2) <=> (x1 = x2) /\ (y1 = y2))
19 ==> ?X Y. !x y. (X(P x y) = x) /\ (Y(P x y) = y)`,
20 GEN_TAC THEN DISCH_TAC THEN
21 EXISTS_TAC `\z:C. @x:A. ?y:B. P x y = z` THEN
22 EXISTS_TAC `\z:C. @y:B. ?x:A. P x y = z` THEN
23 REPEAT GEN_TAC THEN ASM_REWRITE_TAC[BETA_THM] THEN
24 CONJ_TAC THEN MATCH_MP_TAC SELECT_UNIQUE THEN GEN_TAC THEN BETA_TAC THEN
25 EQ_TAC THEN STRIP_TAC THEN ASM_REWRITE_TAC[] THEN
26 W(EXISTS_TAC o rand o snd o dest_exists o snd) THEN REFL_TAC);;
28 (* ------------------------------------------------------------------------- *)
29 (* Define an injective pairing function on ":num". *)
30 (* ------------------------------------------------------------------------- *)
32 let NUMPAIR = new_definition
33 `NUMPAIR x y = (2 EXP x) * (2 * y + 1)`;;
35 let NUMPAIR_INJ_LEMMA = prove
36 (`!x1 y1 x2 y2. (NUMPAIR x1 y1 = NUMPAIR x2 y2) ==> (x1 = x2)`,
37 REWRITE_TAC[NUMPAIR] THEN REPEAT(INDUCT_TAC THEN GEN_TAC) THEN
38 ASM_REWRITE_TAC[EXP; GSYM MULT_ASSOC; ARITH; EQ_MULT_LCANCEL;
39 NOT_SUC; GSYM NOT_SUC; SUC_INJ] THEN
40 DISCH_THEN(MP_TAC o AP_TERM `EVEN`) THEN
41 REWRITE_TAC[EVEN_MULT; EVEN_ADD; ARITH]);;
43 let NUMPAIR_INJ = prove
44 (`!x1 y1 x2 y2. (NUMPAIR x1 y1 = NUMPAIR x2 y2) <=> (x1 = x2) /\ (y1 = y2)`,
45 REPEAT GEN_TAC THEN EQ_TAC THEN DISCH_TAC THEN ASM_REWRITE_TAC[] THEN
46 FIRST_ASSUM(SUBST_ALL_TAC o MATCH_MP NUMPAIR_INJ_LEMMA) THEN
47 POP_ASSUM MP_TAC THEN REWRITE_TAC[NUMPAIR] THEN
48 REWRITE_TAC[EQ_MULT_LCANCEL; EQ_ADD_RCANCEL; EXP_EQ_0; ARITH]);;
50 let NUMPAIR_DEST = new_specification
52 (MATCH_MP INJ_INVERSE2 NUMPAIR_INJ);;
54 (* ------------------------------------------------------------------------- *)
55 (* Also, an injective map bool->num->num (even easier!) *)
56 (* ------------------------------------------------------------------------- *)
58 let NUMSUM = new_definition
59 `NUMSUM b x = if b then SUC(2 * x) else 2 * x`;;
61 let NUMSUM_INJ = prove
62 (`!b1 x1 b2 x2. (NUMSUM b1 x1 = NUMSUM b2 x2) <=> (b1 = b2) /\ (x1 = x2)`,
63 REPEAT GEN_TAC THEN EQ_TAC THEN DISCH_TAC THEN ASM_REWRITE_TAC[] THEN
64 POP_ASSUM(MP_TAC o REWRITE_RULE[NUMSUM]) THEN
65 DISCH_THEN(fun th -> MP_TAC th THEN MP_TAC(AP_TERM `EVEN` th)) THEN
66 REPEAT COND_CASES_TAC THEN REWRITE_TAC[EVEN; EVEN_DOUBLE] THEN
67 REWRITE_TAC[SUC_INJ; EQ_MULT_LCANCEL; ARITH]);;
69 let NUMSUM_DEST = new_specification
70 ["NUMLEFT"; "NUMRIGHT"]
71 (MATCH_MP INJ_INVERSE2 NUMSUM_INJ);;
73 (* ------------------------------------------------------------------------- *)
74 (* Injection num->Z, where Z == num->A->bool. *)
75 (* ------------------------------------------------------------------------- *)
77 let INJN = new_definition
78 `INJN (m:num) = \(n:num) (a:A). n = m`;;
81 (`!n1 n2. (INJN n1 :num->A->bool = INJN n2) <=> (n1 = n2)`,
82 REPEAT GEN_TAC THEN EQ_TAC THEN DISCH_TAC THEN ASM_REWRITE_TAC[] THEN
83 POP_ASSUM(MP_TAC o C AP_THM `n1:num` o REWRITE_RULE[INJN]) THEN
84 DISCH_THEN(MP_TAC o C AP_THM `a:A`) THEN REWRITE_TAC[BETA_THM]);;
86 (* ------------------------------------------------------------------------- *)
87 (* Injection A->Z, where Z == num->A->bool. *)
88 (* ------------------------------------------------------------------------- *)
90 let INJA = new_definition
91 `INJA (a:A) = \(n:num) b. b = a`;;
94 (`!a1 a2. (INJA a1 = INJA a2) <=> (a1:A = a2)`,
95 REPEAT GEN_TAC THEN REWRITE_TAC[INJA; FUN_EQ_THM] THEN EQ_TAC THENL
96 [DISCH_THEN(MP_TAC o SPEC `a1:A`) THEN REWRITE_TAC[];
97 DISCH_THEN SUBST1_TAC THEN REWRITE_TAC[]]);;
99 (* ------------------------------------------------------------------------- *)
100 (* Injection (num->Z)->Z, where Z == num->A->bool. *)
101 (* ------------------------------------------------------------------------- *)
103 let INJF = new_definition
104 `INJF (f:num->(num->A->bool)) = \n. f (NUMFST n) (NUMSND n)`;;
107 (`!f1 f2. (INJF f1 :num->A->bool = INJF f2) <=> (f1 = f2)`,
108 REPEAT GEN_TAC THEN EQ_TAC THEN DISCH_TAC THEN ASM_REWRITE_TAC[] THEN
109 REWRITE_TAC[FUN_EQ_THM] THEN
110 MAP_EVERY X_GEN_TAC [`n:num`; `m:num`; `a:A`] THEN
111 POP_ASSUM(MP_TAC o REWRITE_RULE[INJF]) THEN
112 DISCH_THEN(MP_TAC o C AP_THM `a:A` o C AP_THM `NUMPAIR n m`) THEN
113 REWRITE_TAC[NUMPAIR_DEST]);;
115 (* ------------------------------------------------------------------------- *)
116 (* Injection Z->Z->Z, where Z == num->A->bool. *)
117 (* ------------------------------------------------------------------------- *)
119 let INJP = new_definition
120 `INJP f1 f2:num->A->bool =
121 \n a. if NUMLEFT n then f1 (NUMRIGHT n) a else f2 (NUMRIGHT n) a`;;
124 (`!(f1:num->A->bool) f1' f2 f2'.
125 (INJP f1 f2 = INJP f1' f2') <=> (f1 = f1') /\ (f2 = f2')`,
126 REPEAT GEN_TAC THEN EQ_TAC THEN DISCH_TAC THEN ASM_REWRITE_TAC[] THEN
127 ONCE_REWRITE_TAC[FUN_EQ_THM] THEN REWRITE_TAC[AND_FORALL_THM] THEN
128 X_GEN_TAC `n:num` THEN POP_ASSUM(MP_TAC o REWRITE_RULE[INJP]) THEN
129 DISCH_THEN(MP_TAC o GEN `b:bool` o C AP_THM `NUMSUM b n`) THEN
130 DISCH_THEN(fun th -> MP_TAC(SPEC `T` th) THEN MP_TAC(SPEC `F` th)) THEN
131 ASM_SIMP_TAC[NUMSUM_DEST; ETA_AX]);;
133 (* ------------------------------------------------------------------------- *)
134 (* Now, set up "constructor" and "bottom" element. *)
135 (* ------------------------------------------------------------------------- *)
137 let ZCONSTR = new_definition
138 `ZCONSTR c i r :num->A->bool
139 = INJP (INJN (SUC c)) (INJP (INJA i) (INJF r))`;;
141 let ZBOT = new_definition
142 `ZBOT = INJP (INJN 0) (@z:num->A->bool. T)`;;
144 let ZCONSTR_ZBOT = prove
145 (`!c i r. ~(ZCONSTR c i r :num->A->bool = ZBOT)`,
146 REWRITE_TAC[ZCONSTR; ZBOT; INJP_INJ; INJN_INJ; NOT_SUC]);;
148 (* ------------------------------------------------------------------------- *)
149 (* Carve out an inductively defined set. *)
150 (* ------------------------------------------------------------------------- *)
152 let ZRECSPACE_RULES,ZRECSPACE_INDUCT,ZRECSPACE_CASES =
153 new_inductive_definition
154 `ZRECSPACE (ZBOT:num->A->bool) /\
155 (!c i r. (!n. ZRECSPACE (r n)) ==> ZRECSPACE (ZCONSTR c i r))`;;
158 new_basic_type_definition "recspace" ("_mk_rec","_dest_rec")
159 (CONJUNCT1 ZRECSPACE_RULES);;
161 (* ------------------------------------------------------------------------- *)
162 (* Define lifted constructors. *)
163 (* ------------------------------------------------------------------------- *)
165 let BOTTOM = new_definition
166 `BOTTOM = _mk_rec (ZBOT:num->A->bool)`;;
168 let CONSTR = new_definition
169 `CONSTR c i r :(A)recspace
170 = _mk_rec (ZCONSTR c i (\n. _dest_rec(r n)))`;;
172 (* ------------------------------------------------------------------------- *)
174 (* ------------------------------------------------------------------------- *)
176 let MK_REC_INJ = prove
177 (`!x y. (_mk_rec x :(A)recspace = _mk_rec y)
178 ==> (ZRECSPACE x /\ ZRECSPACE y ==> (x = y))`,
179 REPEAT GEN_TAC THEN DISCH_TAC THEN
180 REWRITE_TAC[snd recspace_tydef] THEN
181 DISCH_THEN(fun th -> ONCE_REWRITE_TAC[GSYM th]) THEN
184 let DEST_REC_INJ = prove
185 (`!x y. (_dest_rec x = _dest_rec y) <=> (x:(A)recspace = y)`,
186 REPEAT GEN_TAC THEN EQ_TAC THEN DISCH_TAC THEN ASM_REWRITE_TAC[] THEN
187 POP_ASSUM(MP_TAC o AP_TERM
188 `_mk_rec:(num->A->bool)->(A)recspace`) THEN
189 REWRITE_TAC[fst recspace_tydef]);;
191 (* ------------------------------------------------------------------------- *)
192 (* Show that the set is freely inductively generated. *)
193 (* ------------------------------------------------------------------------- *)
195 let CONSTR_BOT = prove
196 (`!c i r. ~(CONSTR c i r :(A)recspace = BOTTOM)`,
197 REPEAT GEN_TAC THEN REWRITE_TAC[CONSTR; BOTTOM] THEN
198 DISCH_THEN(MP_TAC o MATCH_MP MK_REC_INJ) THEN
199 REWRITE_TAC[ZCONSTR_ZBOT; ZRECSPACE_RULES] THEN
200 MATCH_MP_TAC(CONJUNCT2 ZRECSPACE_RULES) THEN
201 REWRITE_TAC[fst recspace_tydef; snd recspace_tydef]);;
203 let CONSTR_INJ = prove
204 (`!c1 i1 r1 c2 i2 r2. (CONSTR c1 i1 r1 :(A)recspace = CONSTR c2 i2 r2) <=>
205 (c1 = c2) /\ (i1 = i2) /\ (r1 = r2)`,
206 REPEAT GEN_TAC THEN EQ_TAC THEN DISCH_TAC THEN ASM_REWRITE_TAC[] THEN
207 POP_ASSUM(MP_TAC o REWRITE_RULE[CONSTR]) THEN
208 DISCH_THEN(MP_TAC o MATCH_MP MK_REC_INJ) THEN
209 W(C SUBGOAL_THEN ASSUME_TAC o funpow 2 lhand o snd) THENL
210 [CONJ_TAC THEN MATCH_MP_TAC(CONJUNCT2 ZRECSPACE_RULES) THEN
211 REWRITE_TAC[fst recspace_tydef; snd recspace_tydef];
212 ASM_REWRITE_TAC[] THEN REWRITE_TAC[ZCONSTR] THEN
213 REWRITE_TAC[INJP_INJ; INJN_INJ; INJF_INJ; INJA_INJ] THEN
214 ONCE_REWRITE_TAC[FUN_EQ_THM] THEN BETA_TAC THEN
215 REWRITE_TAC[SUC_INJ; DEST_REC_INJ]]);;
217 let CONSTR_IND = prove
219 (!c i r. (!n. P(r n)) ==> P(CONSTR c i r))
220 ==> !x:(A)recspace. P(x)`,
221 REPEAT STRIP_TAC THEN
222 MP_TAC(SPEC `\z:num->A->bool. ZRECSPACE(z) /\ P(_mk_rec z)`
223 ZRECSPACE_INDUCT) THEN
224 BETA_TAC THEN ASM_REWRITE_TAC[ZRECSPACE_RULES; GSYM BOTTOM] THEN
225 W(C SUBGOAL_THEN ASSUME_TAC o funpow 2 lhand o snd) THENL
226 [REPEAT GEN_TAC THEN REWRITE_TAC[FORALL_AND_THM] THEN
227 REPEAT STRIP_TAC THENL
228 [MATCH_MP_TAC(CONJUNCT2 ZRECSPACE_RULES) THEN ASM_REWRITE_TAC[];
229 FIRST_ASSUM(ANTE_RES_THEN MP_TAC) THEN
230 REWRITE_TAC[CONSTR] THEN
231 RULE_ASSUM_TAC(REWRITE_RULE[snd recspace_tydef]) THEN
232 ASM_SIMP_TAC[ETA_AX]];
233 ASM_REWRITE_TAC[] THEN
234 DISCH_THEN(MP_TAC o SPEC `_dest_rec (x:(A)recspace)`) THEN
235 REWRITE_TAC[fst recspace_tydef] THEN
236 REWRITE_TAC[ITAUT `(a ==> a /\ b) <=> (a ==> b)`] THEN
237 DISCH_THEN MATCH_MP_TAC THEN
238 REWRITE_TAC[fst recspace_tydef; snd recspace_tydef]]);;
240 (* ------------------------------------------------------------------------- *)
241 (* Now prove the recursion theorem (this subcase is all we need). *)
242 (* ------------------------------------------------------------------------- *)
244 let CONSTR_REC = prove
245 (`!Fn:num->A->(num->(A)recspace)->(num->B)->B.
246 ?f. (!c i r. f (CONSTR c i r) = Fn c i r (\n. f (r n)))`,
247 REPEAT STRIP_TAC THEN (MP_TAC o prove_inductive_relations_exist)
248 `(Z:(A)recspace->B->bool) BOTTOM b /\
249 (!c i r y. (!n. Z (r n) (y n)) ==> Z (CONSTR c i r) (Fn c i r y))` THEN
250 DISCH_THEN(CHOOSE_THEN(CONJUNCTS_THEN2 STRIP_ASSUME_TAC MP_TAC)) THEN
251 DISCH_THEN(CONJUNCTS_THEN2 ASSUME_TAC (ASSUME_TAC o GSYM)) THEN
252 SUBGOAL_THEN `!x. ?!y. (Z:(A)recspace->B->bool) x y` MP_TAC THENL
253 [W(MP_TAC o PART_MATCH rand CONSTR_IND o snd) THEN
254 DISCH_THEN MATCH_MP_TAC THEN CONJ_TAC THEN REPEAT GEN_TAC THENL
255 [FIRST_ASSUM(fun t -> GEN_REWRITE_TAC BINDER_CONV [GSYM t]) THEN
256 REWRITE_TAC[GSYM CONSTR_BOT; EXISTS_UNIQUE_REFL];
257 DISCH_THEN(MP_TAC o REWRITE_RULE[EXISTS_UNIQUE_THM; FORALL_AND_THM]) THEN
258 DISCH_THEN(CONJUNCTS_THEN2 MP_TAC ASSUME_TAC) THEN
259 DISCH_THEN(MP_TAC o REWRITE_RULE[SKOLEM_THM]) THEN
260 DISCH_THEN(X_CHOOSE_THEN `y:num->B` ASSUME_TAC) THEN
261 REWRITE_TAC[EXISTS_UNIQUE_THM] THEN
262 FIRST_ASSUM(fun th -> CHANGED_TAC(ONCE_REWRITE_TAC[GSYM th])) THEN
264 [EXISTS_TAC `(Fn:num->A->(num->(A)recspace)->(num->B)->B) c i r y` THEN
265 REWRITE_TAC[CONSTR_BOT; CONSTR_INJ; GSYM CONJ_ASSOC] THEN
266 REWRITE_TAC[UNWIND_THM1; RIGHT_EXISTS_AND_THM] THEN
267 EXISTS_TAC `y:num->B` THEN ASM_REWRITE_TAC[];
268 REWRITE_TAC[CONSTR_BOT; CONSTR_INJ; GSYM CONJ_ASSOC] THEN
269 REWRITE_TAC[UNWIND_THM1; RIGHT_EXISTS_AND_THM] THEN
270 REPEAT STRIP_TAC THEN ASM_REWRITE_TAC[] THEN
271 REPEAT AP_TERM_TAC THEN ONCE_REWRITE_TAC[FUN_EQ_THM] THEN
272 X_GEN_TAC `w:num` THEN FIRST_ASSUM MATCH_MP_TAC THEN
273 EXISTS_TAC `w:num` THEN ASM_REWRITE_TAC[]]];
274 REWRITE_TAC[UNIQUE_SKOLEM_ALT] THEN
275 DISCH_THEN(X_CHOOSE_THEN `fn:(A)recspace->B` (ASSUME_TAC o GSYM)) THEN
276 EXISTS_TAC `fn:(A)recspace->B` THEN ASM_REWRITE_TAC[] THEN
277 REPEAT GEN_TAC THEN FIRST_ASSUM MATCH_MP_TAC THEN GEN_TAC THEN
278 FIRST_ASSUM(fun th -> GEN_REWRITE_TAC I [GSYM th]) THEN
279 REWRITE_TAC[BETA_THM]]);;
281 (* ------------------------------------------------------------------------- *)
282 (* The following is useful for coding up functions casewise. *)
283 (* ------------------------------------------------------------------------- *)
285 let FCONS = new_recursive_definition num_RECURSION
286 `(!a f. FCONS (a:A) f 0 = a) /\
287 (!a f n. FCONS (a:A) f (SUC n) = f n)`;;
289 let FCONS_UNDO = prove
290 (`!f:num->A. f = FCONS (f 0) (f o SUC)`,
291 GEN_TAC THEN REWRITE_TAC[FUN_EQ_THM] THEN
292 INDUCT_TAC THEN REWRITE_TAC[FCONS; o_THM]);;
294 let FNIL = new_definition
295 `FNIL (n:num) = @x:A. T`;;
297 (* ------------------------------------------------------------------------- *)
298 (* The initial mutual type definition function, with a type-restricted *)
299 (* recursion theorem. *)
300 (* ------------------------------------------------------------------------- *)
302 let define_type_raw =
304 (* ----------------------------------------------------------------------- *)
305 (* Handy utility to produce "SUC o SUC o SUC ..." form of numeral. *)
306 (* ----------------------------------------------------------------------- *)
309 let zero = `0` and suc = `SUC` in
310 fun n -> funpow n (curry mk_comb suc) zero in
312 (* ----------------------------------------------------------------------- *)
313 (* Eliminate local "definitions" in hyps. *)
314 (* ----------------------------------------------------------------------- *)
317 let SCRUB_EQUATION eq (th,insts) = (*HA*)
318 let eq' = itlist subst (map (fun t -> [t]) insts) eq in
319 let l,r = dest_eq eq' in
320 (MP (INST [r,l] (DISCH eq' th)) (REFL r),(r,l)::insts) in
322 (* ----------------------------------------------------------------------- *)
323 (* Proves existence of model (inductively); use pseudo-constructors. *)
325 (* Returns suitable definitions of constructors in terms of CONSTR, and *)
326 (* the rule and induction theorems from the inductive relation package. *)
327 (* ----------------------------------------------------------------------- *)
329 let justify_inductive_type_model =
330 let t_tm = `T` and n_tm = `n:num` and beps_tm = `@x:bool. T` in
331 let rec munion s1 s2 =
332 if s1 = [] then s2 else
335 try let _,s2' = remove (fun h2 -> h2 = h1) s2 in h1::(munion s1' s2')
336 with Failure _ -> h1::(munion s1' s2) in
338 let newtys,rights = unzip def in
339 let tyargls = itlist ((@) o map snd) rights [] in
340 let alltys = itlist (munion o C subtract newtys) tyargls [] in
341 let epstms = map (fun ty -> mk_select(mk_var("v",ty),t_tm)) alltys in
343 try end_itlist (fun ty1 ty2 -> mk_type("prod",[ty1;ty2])) alltys
344 with Failure _ -> bool_ty in
345 let recty = mk_type("recspace",[pty]) in
346 let constr = mk_const("CONSTR",[pty,aty]) in
347 let fcons = mk_const("FCONS",[recty,aty]) in
348 let bot = mk_const("BOTTOM",[pty,aty]) in
349 let bottail = mk_abs(n_tm,bot) in
350 let mk_constructor n (cname,cargs) =
351 let ttys = map (fun ty -> if mem ty newtys then recty else ty) cargs in
352 let args = make_args "a" [] ttys in
353 let rargs,iargs = partition (fun t -> type_of t = recty) args in
354 let rec mk_injector epstms alltys iargs =
355 if alltys = [] then [] else
356 let ty = hd alltys in
357 try let a,iargs' = remove (fun t -> type_of t = ty) iargs in
358 a::(mk_injector (tl epstms) (tl alltys) iargs')
360 (hd epstms)::(mk_injector (tl epstms) (tl alltys) iargs) in
362 try end_itlist (curry mk_pair) (mk_injector epstms alltys iargs)
363 with Failure _ -> beps_tm in
364 let rarg = itlist (mk_binop fcons) rargs bottail in
365 let conty = itlist mk_fun_ty (map type_of args) recty in
366 let condef = list_mk_comb(constr,[sucivate n; iarg; rarg]) in
367 mk_eq(mk_var(cname,conty),list_mk_abs(args,condef)) in
368 let rec mk_constructors n rights =
369 if rights = [] then [] else
370 (mk_constructor n (hd rights))::(mk_constructors (n + 1) (tl rights)) in
371 let condefs = mk_constructors 0 (itlist (@) rights []) in
372 let conths = map ASSUME condefs in
373 let predty = mk_fun_ty recty bool_ty in
374 let edefs = itlist (fun (x,l) acc -> map (fun t -> x,t) l @ acc) def [] in
375 let idefs = map2 (fun (r,(_,atys)) def -> (r,atys),def) edefs condefs in
376 let mk_rule ((r,a),condef) =
377 let left,right = dest_eq condef in
378 let args,bod = strip_abs right in
379 let lapp = list_mk_comb(left,args) in
381 (fun arg argty sofar ->
382 if mem argty newtys then
383 mk_comb(mk_var(dest_vartype argty,predty),arg)::sofar
384 else sofar) args a [] in
385 let conc = mk_comb(mk_var(dest_vartype r,predty),lapp) in
386 let rule = if conds = [] then conc
387 else mk_imp(list_mk_conj conds,conc) in
388 list_mk_forall(args,rule) in
389 let rules = list_mk_conj (map mk_rule idefs) in
390 let th0 = derive_nonschematic_inductive_relations rules in
391 let th1 = prove_monotonicity_hyps th0 in
392 let th2a,th2bc = CONJ_PAIR th1 in
393 let th2b = CONJUNCT1 th2bc in
396 (* ----------------------------------------------------------------------- *)
397 (* Shows that the predicates defined by the rules are all nonempty. *)
398 (* (This could be done much more efficiently/cleverly, but it's OK.) *)
399 (* ----------------------------------------------------------------------- *)
401 let prove_model_inhabitation rth =
402 let srules = map SPEC_ALL (CONJUNCTS rth) in
403 let imps,bases = partition (is_imp o concl) srules in
404 let concs = map concl bases @ map (rand o concl) imps in
405 let preds = setify (map (repeat rator) concs) in
406 let rec exhaust_inhabitations ths sofar =
407 let dunnit = setify(map (fst o strip_comb o concl) sofar) in
409 (fun th -> not (mem (fst(strip_comb(rand(concl th)))) dunnit)) ths in
410 if useful = [] then sofar else
411 let follow_horn thm =
412 let preds = map (fst o strip_comb) (conjuncts(lhand(concl thm))) in
414 (fun p -> find (fun th -> fst(strip_comb(concl th)) = p) sofar)
416 MATCH_MP thm (end_itlist CONJ asms) in
417 let newth = tryfind follow_horn useful in
418 exhaust_inhabitations ths (newth::sofar) in
419 let ithms = exhaust_inhabitations imps bases in
421 (fun p -> find (fun th -> fst(strip_comb(concl th)) = p) ithms) preds in
424 (* ----------------------------------------------------------------------- *)
425 (* Makes a type definition for one of the defined subsets. *)
426 (* ----------------------------------------------------------------------- *)
428 let define_inductive_type cdefs exth =
429 let extm = concl exth in
430 let epred = fst(strip_comb extm) in
431 let ename = fst(dest_var epred) in
432 let th1 = ASSUME (find (fun eq -> lhand eq = epred) (hyp exth)) in
433 let th2 = TRANS th1 (SUBS_CONV cdefs (rand(concl th1))) in
434 let th3 = EQ_MP (AP_THM th2 (rand extm)) exth in
435 let th4,_ = itlist SCRUB_EQUATION (hyp th3) (th3,[]) in
436 let mkname = "_mk_"^ename and destname = "_dest_"^ename in
437 let bij1,bij2 = new_basic_type_definition ename (mkname,destname) th4 in
438 let bij2a = AP_THM th2 (rand(rand(concl bij2))) in
439 let bij2b = TRANS bij2a bij2 in
442 (* ----------------------------------------------------------------------- *)
443 (* Defines a type constructor corresponding to current pseudo-constructor. *)
444 (* ----------------------------------------------------------------------- *)
446 let define_inductive_type_constructor defs consindex th =
447 let avs,bod = strip_forall(concl th) in
449 if is_imp bod then conjuncts(lhand bod),rand bod else [],bod in
450 let asmlist = map dest_comb asms in
451 let cpred,cterm = dest_comb conc in
452 let oldcon,oldargs = strip_comb cterm in
454 try let dest = snd(assoc (rev_assoc v asmlist) consindex) in
455 let ty' = hd(snd(dest_type(type_of dest))) in
456 let v' = mk_var(fst(dest_var v),ty') in
458 with Failure _ -> v,v in
459 let newrights,newargs = unzip(map modify_arg oldargs) in
460 let retmk = fst(assoc cpred consindex) in
461 let defbod = mk_comb(retmk,list_mk_comb(oldcon,newrights)) in
462 let defrt = list_mk_abs(newargs,defbod) in
463 let expth = find (fun th -> lhand(concl th) = oldcon) defs in
464 let rexpth = SUBS_CONV [expth] defrt in
465 let deflf = mk_var(fst(dest_var oldcon),type_of defrt) in
466 let defth = new_definition(mk_eq(deflf,rand(concl rexpth))) in
467 TRANS defth (SYM rexpth) in
469 (* ----------------------------------------------------------------------- *)
470 (* Instantiate the induction theorem on the representatives to transfer *)
471 (* it to the new type(s). Uses "\x. rep-pred(x) /\ P(mk x)" for "P". *)
472 (* ----------------------------------------------------------------------- *)
474 let instantiate_induction_theorem consindex ith =
475 let avs,bod = strip_forall(concl ith) in
476 let corlist = map((repeat rator F_F repeat rator) o dest_imp o body o rand)
477 (conjuncts(rand bod)) in
478 let consindex' = map (fun v -> let w = rev_assoc v corlist in
479 w,assoc w consindex) avs in
480 let recty = (hd o snd o dest_type o type_of o fst o snd o hd) consindex in
481 let newtys = map (hd o snd o dest_type o type_of o snd o snd) consindex' in
482 let ptypes = map (C mk_fun_ty bool_ty) newtys in
483 let preds = make_args "P" [] ptypes in
484 let args = make_args "x" [] (map (K recty) preds) in
485 let lambs = map2 (fun (r,(m,d)) (p,a) ->
486 mk_abs(a,mk_conj(mk_comb(r,a),mk_comb(p,mk_comb(m,a)))))
487 consindex' (zip preds args) in
490 (* ----------------------------------------------------------------------- *)
491 (* Reduce a single clause of the postulated induction theorem (old_ver) ba *)
492 (* to the kind wanted for the new type (new_ver); |- new_ver ==> old_ver *)
493 (* ----------------------------------------------------------------------- *)
495 let pullback_induction_clause tybijpairs conthms =
496 let PRERULE = GEN_REWRITE_RULE (funpow 3 RAND_CONV) (map SYM conthms) in
497 let IPRULE = SYM o GEN_REWRITE_RULE I (map snd tybijpairs) in
499 let avs,bimp = strip_forall tm in
501 let ant,con = dest_imp bimp in
502 let ths = map (CONV_RULE BETA_CONV) (CONJUNCTS (ASSUME ant)) in
503 let tths,pths = unzip (map CONJ_PAIR ths) in
504 let tth = MATCH_MP (SPEC_ALL rthm) (end_itlist CONJ tths) in
505 let mths = map IPRULE (tth::tths) in
506 let conth1 = BETA_CONV con in
507 let contm1 = rand(concl conth1) in
508 let conth2 = TRANS conth1
509 (AP_TERM (rator contm1) (SUBS_CONV (tl mths) (rand contm1))) in
510 let conth3 = PRERULE conth2 in
511 let lctms = map concl pths in
512 let asmin = mk_imp(list_mk_conj lctms,rand(rand(concl conth3))) in
513 let argsin = map rand (conjuncts(lhand asmin)) in
515 map (fun tm -> mk_var(fst(dest_var(rand tm)),type_of tm)) argsin in
516 let asmgen = subst (zip argsgen argsin) asmin in
518 list_mk_forall(snd(strip_comb(rand(rand asmgen))),asmgen) in
519 let th1 = INST (zip argsin argsgen) (SPEC_ALL (ASSUME asmquant)) in
520 let th2 = MP th1 (end_itlist CONJ pths) in
521 let th3 = EQ_MP (SYM conth3) (CONJ tth th2) in
522 DISCH asmquant (GENL avs (DISCH ant th3))
525 let conth2 = BETA_CONV con in
526 let tth = PART_MATCH I rthm (lhand(rand(concl conth2))) in
527 let conth3 = PRERULE conth2 in
528 let asmgen = rand(rand(concl conth3)) in
529 let asmquant = list_mk_forall(snd(strip_comb(rand asmgen)),asmgen) in
530 let th2 = SPEC_ALL (ASSUME asmquant) in
531 let th3 = EQ_MP (SYM conth3) (CONJ tth th2) in
532 DISCH asmquant (GENL avs th3) in
534 (* ----------------------------------------------------------------------- *)
535 (* Finish off a consequence of the induction theorem. *)
536 (* ----------------------------------------------------------------------- *)
538 let finish_induction_conclusion consindex tybijpairs =
539 let tybij1,tybij2 = unzip tybijpairs in
541 GEN_REWRITE_RULE (LAND_CONV o LAND_CONV o RAND_CONV) tybij1 o
542 GEN_REWRITE_RULE LAND_CONV tybij2
543 and FINRULE = GEN_REWRITE_RULE RAND_CONV tybij1 in
545 let av,bimp = dest_forall(concl th) in
546 let pv = lhand(body(rator(rand bimp))) in
547 let p,v = dest_comb pv in
548 let mk,dest = assoc p consindex in
549 let ty = hd(snd(dest_type(type_of dest))) in
550 let v' = mk_var(fst(dest_var v),ty) in
551 let dv = mk_comb(dest,v') in
552 let th1 = PRERULE (SPEC dv th) in
553 let th2 = MP th1 (REFL (rand(lhand(concl th1)))) in
554 let th3 = CONV_RULE BETA_CONV th2 in
555 GEN v' (FINRULE (CONJUNCT2 th3)) in
557 (* ----------------------------------------------------------------------- *)
558 (* Derive the induction theorem. *)
559 (* ----------------------------------------------------------------------- *)
561 let derive_induction_theorem consindex tybijpairs conthms iith rth =
563 (pullback_induction_clause tybijpairs conthms)
564 (CONJUNCTS rth) (conjuncts(lhand(concl iith))) in
565 let asm = list_mk_conj(map (lhand o concl) bths) in
566 let ths = map2 MP bths (CONJUNCTS (ASSUME asm)) in
567 let th1 = MP iith (end_itlist CONJ ths) in
568 let th2 = end_itlist CONJ (map
569 (finish_induction_conclusion consindex tybijpairs) (CONJUNCTS th1)) in
570 let th3 = DISCH asm th2 in
571 let preds = map (rator o body o rand) (conjuncts(rand(concl th3))) in
572 let th4 = GENL preds th3 in
573 let pasms = filter (C mem (map fst consindex) o lhand) (hyp th4) in
574 let th5 = itlist DISCH pasms th4 in
575 let th6,_ = itlist SCRUB_EQUATION (hyp th5) (th5,[]) in
576 let th7 = UNDISCH_ALL th6 in
577 fst (itlist SCRUB_EQUATION (hyp th7) (th7,[])) in
579 (* ----------------------------------------------------------------------- *)
580 (* Create the recursive functions and eliminate pseudo-constructors. *)
581 (* (These are kept just long enough to derive the key property.) *)
582 (* ----------------------------------------------------------------------- *)
584 let create_recursive_functions tybijpairs consindex conthms rth =
585 let domtys = map (hd o snd o dest_type o type_of o snd o snd) consindex in
586 let recty = (hd o snd o dest_type o type_of o fst o snd o hd) consindex in
587 let ranty = mk_vartype "Z" in
588 let fn = mk_var("fn",mk_fun_ty recty ranty)
589 and fns = make_args "fn" [] (map (C mk_fun_ty ranty) domtys) in
590 let args = make_args "a" [] domtys in
591 let rights = map2 (fun (_,(_,d)) a -> mk_abs(a,mk_comb(fn,mk_comb(d,a))))
593 let eqs = map2 (curry mk_eq) fns rights in
594 let fdefs = map ASSUME eqs in
595 let fxths1 = map (fun th1 -> tryfind (fun th2 -> MK_COMB(th2,th1)) fdefs)
597 let fxths2 = map (fun th -> TRANS th (BETA_CONV (rand(concl th)))) fxths1 in
598 let mk_tybijcons (th1,th2) =
599 let th3 = INST [rand(lhand(concl th1)),rand(lhand(concl th2))] th2 in
600 let th4 = AP_TERM (rator(lhand(rand(concl th2)))) th1 in
601 EQ_MP (SYM th3) th4 in
602 let SCONV = GEN_REWRITE_CONV I (map mk_tybijcons tybijpairs)
603 and ERULE = GEN_REWRITE_RULE I (map snd tybijpairs) in
604 let simplify_fxthm rthm fxth =
605 let pat = funpow 4 rand (concl fxth) in
606 if is_imp(repeat (snd o dest_forall) (concl rthm)) then
607 let th1 = PART_MATCH (rand o rand) rthm pat in
608 let tms1 = conjuncts(lhand(concl th1)) in
609 let ths2 = map (fun t -> EQ_MP (SYM(SCONV t)) TRUTH) tms1 in
610 ERULE (MP th1 (end_itlist CONJ ths2))
612 ERULE (PART_MATCH rand rthm pat) in
613 let fxths3 = map2 simplify_fxthm (CONJUNCTS rth) fxths2 in
614 let fxths4 = map2 (fun th1 -> TRANS th1 o AP_TERM fn) fxths2 fxths3 in
615 let cleanup_fxthm cth fxth =
616 let tms = snd(strip_comb(rand(rand(concl fxth)))) in
617 let kth = RIGHT_BETAS tms (ASSUME (hd(hyp cth))) in
618 TRANS fxth (AP_TERM fn kth) in
619 let fxth5 = end_itlist CONJ (map2 cleanup_fxthm conthms fxths4) in
620 let pasms = filter (C mem (map fst consindex) o lhand) (hyp fxth5) in
621 let fxth6 = itlist DISCH pasms fxth5 in
623 itlist SCRUB_EQUATION (itlist (union o hyp) conthms []) (fxth6,[]) in
624 let fxth8 = UNDISCH_ALL fxth7 in
625 fst (itlist SCRUB_EQUATION (subtract (hyp fxth8) eqs) (fxth8,[])) in
627 (* ----------------------------------------------------------------------- *)
628 (* Create a function for recursion clause. *)
629 (* ----------------------------------------------------------------------- *)
631 let create_recursion_iso_constructor =
632 let s = `s:num->Z` in
634 let numty = `:num` in
635 let rec extract_arg tup v =
636 if v = tup then REFL tup else
637 let t1,t2 = dest_pair tup in
638 let PAIR_th = ISPECL [t1;t2] (if free_in v t1 then FST else SND) in
639 let tup' = rand(concl PAIR_th) in
640 if tup' = v then PAIR_th else
641 let th = extract_arg (rand(concl PAIR_th)) v in
642 SUBS[SYM PAIR_th] th in
644 let recty = hd(snd(dest_type(type_of(fst(hd consindex))))) in
645 let domty = hd(snd(dest_type recty)) in
646 let i = mk_var("i",domty)
647 and r = mk_var("r",mk_fun_ty numty recty) in
648 let mks = map (fst o snd) consindex in
649 let mkindex = map (fun t -> hd(tl(snd(dest_type(type_of t)))),t) mks in
651 let artms = snd(strip_comb(rand(rand(concl cth)))) in
652 let artys = mapfilter (type_of o rand) artms in
653 let args,bod = strip_abs(rand(hd(hyp cth))) in
654 let ccitm,rtm = dest_comb bod in
655 let cctm,itm = dest_comb ccitm in
656 let rargs,iargs = partition (C free_in rtm) args in
657 let xths = map (extract_arg itm) iargs in
658 let cargs' = map (subst [i,itm] o lhand o concl) xths in
659 let indices = map sucivate (0--(length rargs - 1)) in
660 let rindexed = map (curry mk_comb r) indices in
661 let rargs' = map2 (fun a rx -> mk_comb(assoc a mkindex,rx))
663 let sargs' = map (curry mk_comb s) indices in
664 let allargs = cargs'@ rargs' @ sargs' in
665 let funty = itlist (mk_fun_ty o type_of) allargs zty in
666 let funname = fst(dest_const(repeat rator (lhand(concl cth))))^"'" in
667 let funarg = mk_var(funname,funty) in
668 list_mk_abs([i;r;s],list_mk_comb(funarg,allargs)) in
670 (* ----------------------------------------------------------------------- *)
671 (* Derive the recursion theorem. *)
672 (* ----------------------------------------------------------------------- *)
674 let derive_recursion_theorem =
675 let CCONV = funpow 3 RATOR_CONV (REPEATC (GEN_REWRITE_CONV I [FCONS])) in
676 fun tybijpairs consindex conthms rath ->
677 let isocons = map (create_recursion_iso_constructor consindex) conthms in
678 let ty = type_of(hd isocons) in
679 let fcons = mk_const("FCONS",[ty,aty])
680 and fnil = mk_const("FNIL",[ty,aty]) in
681 let bigfun = itlist (mk_binop fcons) isocons fnil in
682 let eth = ISPEC bigfun CONSTR_REC in
683 let fn = rator(rand(hd(conjuncts(concl rath)))) in
684 let betm = let v,bod = dest_abs(rand(concl eth)) in vsubst[fn,v] bod in
685 let LCONV = REWR_CONV (ASSUME betm) in
687 map (fun t -> RIGHT_BETAS [bndvar(rand t)] (ASSUME t)) (hyp rath) in
688 let SIMPER = PURE_REWRITE_RULE
689 (map SYM fnths @ map fst tybijpairs @ [FST; SND; FCONS; BETA_THM]) in
690 let hackdown_rath th =
691 let ltm,rtm = dest_eq(concl th) in
692 let wargs = snd(strip_comb(rand ltm)) in
693 let th1 = TRANS th (LCONV rtm) in
694 let th2 = TRANS th1 (CCONV (rand(concl th1))) in
695 let th3 = TRANS th2 (funpow 2 RATOR_CONV BETA_CONV (rand(concl th2))) in
696 let th4 = TRANS th3 (RATOR_CONV BETA_CONV (rand(concl th3))) in
697 let th5 = TRANS th4 (BETA_CONV (rand(concl th4))) in
698 GENL wargs (SIMPER th5) in
699 let rthm = end_itlist CONJ (map hackdown_rath (CONJUNCTS rath)) in
701 let unseqs = filter is_eq (hyp rthm) in
702 let tys = map (hd o snd o dest_type o type_of o snd o snd) consindex in
704 (fun t -> hd(snd(dest_type(type_of(lhand t)))) = ty) unseqs) tys in
705 let rethm = itlist EXISTS_EQUATION seqs rthm in
706 let fethm = CHOOSE(fn,eth) rethm in
707 let pcons = map (repeat rator o rand o repeat (snd o dest_forall))
708 (conjuncts(concl rthm)) in
711 (* ----------------------------------------------------------------------- *)
712 (* Basic function: returns induction and recursion separately. No parser. *)
713 (* ----------------------------------------------------------------------- *)
716 let defs,rth,ith = justify_inductive_type_model def in
717 let neths = prove_model_inhabitation rth in
718 let tybijpairs = map (define_inductive_type defs) neths in
719 let preds = map (repeat rator o concl) neths in
721 (fun (th,_) -> let tm = lhand(concl th) in rator tm,rator(rand tm))
723 let consindex = zip preds mkdests in
724 let condefs = map (define_inductive_type_constructor defs consindex)
727 (fun th -> let args = fst(strip_abs(rand(concl th))) in
728 RIGHT_BETAS args th) condefs in
729 let iith = instantiate_induction_theorem consindex ith in
730 let fth = derive_induction_theorem consindex tybijpairs conthms iith rth in
731 let rath = create_recursive_functions tybijpairs consindex conthms rth in
732 let kth = derive_recursion_theorem tybijpairs consindex conthms rath in
735 (* ------------------------------------------------------------------------- *)
736 (* Parser to present a nice interface a la Melham. *)
737 (* ------------------------------------------------------------------------- *)
739 let parse_inductive_type_specification =
740 let parse_type_loc src =
741 let pty,rst = parse_pretype src in
742 type_of_pretype pty,rst in
743 let parse_type_conapp src =
745 match src with (Ident cn)::sps -> cn,sps
747 let tys,rst = many parse_type_loc sps in
749 let parse_type_clause src =
751 match src with (Ident tn)::sps -> tn,sps
753 let tys,rst = (a (Ident "=") ++ listof parse_type_conapp (a (Resword "|"))
754 "type definition clauses"
756 (mk_vartype tn,tys),rst in
757 let parse_type_definition =
758 listof parse_type_clause (a (Resword ";")) "type definition" in
760 let spec,rst = (parse_type_definition o lex o explode) s in
761 if rst = [] then spec
762 else failwith "parse_inductive_type_specification: junk after def";;
764 (* ------------------------------------------------------------------------- *)
765 (* Use this temporary version to define the sum type. *)
766 (* ------------------------------------------------------------------------- *)
768 let sum_INDUCT,sum_RECURSION =
769 define_type_raw (parse_inductive_type_specification "sum = INL A | INR B");;
771 let OUTL = new_recursive_definition sum_RECURSION
772 `OUTL (INL x :A+B) = x`;;
774 let OUTR = new_recursive_definition sum_RECURSION
775 `OUTR (INR y :A+B) = y`;;
777 (* ------------------------------------------------------------------------- *)
778 (* Generalize the recursion theorem to multiple domain types. *)
779 (* (We needed to use a single type to justify it via a proforma theorem.) *)
781 (* NB! Before this is called nontrivially (i.e. more than one new type) *)
782 (* the type constructor ":sum", used internally, must have been defined. *)
783 (* ------------------------------------------------------------------------- *)
785 let define_type_raw =
786 let generalize_recursion_theorem =
787 let ELIM_OUTCOMBS = GEN_REWRITE_RULE TOP_DEPTH_CONV [OUTL; OUTR] in
789 let k = length tys in
790 if k = 1 then hd tys else
791 let tys1,tys2 = chop_list (k / 2) tys in
792 mk_type("sum",[mk_sum tys1; mk_sum tys2]) in
795 if is_vartype ty then [mk_var("x",ty)] else
796 let _,[ty1;ty2] = dest_type ty in
797 let inls1 = mk_inls ty1
798 and inls2 = mk_inls ty2 in
799 let inl = mk_const("INL",[ty1,aty; ty2,bty])
800 and inr = mk_const("INR",[ty1,aty; ty2,bty]) in
801 map (curry mk_comb inl) inls1 @ map (curry mk_comb inr) inls2 in
802 fun ty -> let bods = mk_inls ty in
803 map (fun t -> mk_abs(find_term is_var t,t)) bods in
805 let rec mk_inls sof ty =
806 if is_vartype ty then [sof] else
807 let _,[ty1;ty2] = dest_type ty in
808 let outl = mk_const("OUTL",[ty1,aty; ty2,bty])
809 and outr = mk_const("OUTR",[ty1,aty; ty2,bty]) in
810 mk_inls (mk_comb(outl,sof)) ty1 @ mk_inls (mk_comb(outr,sof)) ty2 in
811 fun ty -> let x = mk_var("x",ty) in
812 map (curry mk_abs x) (mk_inls x ty) in
813 let mk_newfun fn outl =
814 let s,ty = dest_var fn in
815 let dty = hd(snd(dest_type ty)) in
816 let x = mk_var("x",dty) in
817 let y,bod = dest_abs outl in
818 let r = mk_abs(x,vsubst[mk_comb(fn,x),y] bod) in
819 let l = mk_var(s,type_of r) in
820 let th1 = ASSUME (mk_eq(l,r)) in
821 RIGHT_BETAS [x] th1 in
823 let avs,ebod = strip_forall(concl th) in
824 let evs,bod = strip_exists ebod in
825 let n = length evs in
826 if n = 1 then th else
827 let tys = map (fun i -> mk_vartype ("Z"^(string_of_int i)))
829 let sty = mk_sum tys in
830 let inls = mk_inls sty
831 and outls = mk_outls sty in
832 let zty = type_of(rand(snd(strip_forall(hd(conjuncts bod))))) in
833 let ith = INST_TYPE [sty,zty] th in
834 let avs,ebod = strip_forall(concl ith) in
835 let evs,bod = strip_exists ebod in
836 let fns' = map2 mk_newfun evs outls in
837 let fnalist = zip evs (map (rator o lhs o concl) fns')
838 and inlalist = zip evs inls
839 and outlalist = zip evs outls in
841 let avs,bod = strip_forall tm in
842 let l,r = dest_eq bod in
843 let fn,args = strip_comb r in
845 (fun a -> let g = genvar(type_of a) in
846 if is_var a then g,g else
847 let outl = assoc (rator a) outlalist in
848 mk_comb(outl,g),g) args in
849 let args',args'' = unzip pargs in
850 let inl = assoc (rator l) inlalist in
851 let rty = hd(snd(dest_type(type_of inl))) in
852 let nty = itlist (mk_fun_ty o type_of) args' rty in
853 let fn' = mk_var(fst(dest_var fn),nty) in
854 let r' = list_mk_abs(args'',mk_comb(inl,list_mk_comb(fn',args'))) in
856 let defs = map hack_clause (conjuncts bod) in
857 let jth = BETA_RULE (SPECL (map fst defs) ith) in
858 let bth = ASSUME (snd(strip_exists(concl jth))) in
859 let finish_clause th =
860 let avs,bod = strip_forall (concl th) in
861 let outl = assoc (rator (lhand bod)) outlalist in
862 GENL avs (BETA_RULE (AP_TERM outl (SPECL avs th))) in
863 let cth = end_itlist CONJ (map finish_clause (CONJUNCTS bth)) in
864 let dth = ELIM_OUTCOMBS cth in
865 let eth = GEN_REWRITE_RULE ONCE_DEPTH_CONV (map SYM fns') dth in
866 let fth = itlist SIMPLE_EXISTS (map snd fnalist) eth in
867 let dtms = map (hd o hyp) fns' in
868 let gth = itlist (fun e th -> let l,r = dest_eq e in
869 MP (INST [r,l] (DISCH e th)) (REFL r)) dtms fth in
870 let hth = PROVE_HYP jth (itlist SIMPLE_CHOOSE evs gth) in
871 let xvs = map (fst o strip_comb o rand o snd o strip_forall)
872 (conjuncts(concl eth)) in
874 fun def -> let ith,rth = define_type_raw def in
875 ith,generalize_recursion_theorem rth;;
877 (* ------------------------------------------------------------------------- *)
878 (* Set up options and lists. *)
879 (* ------------------------------------------------------------------------- *)
881 let option_INDUCT,option_RECURSION =
883 (parse_inductive_type_specification "option = NONE | SOME A");;
885 let list_INDUCT,list_RECURSION =
887 (parse_inductive_type_specification "list = NIL | CONS A list");;
889 (* ------------------------------------------------------------------------- *)
890 (* Tools for proving injectivity and distinctness of constructors. *)
891 (* ------------------------------------------------------------------------- *)
893 let prove_constructors_injective =
894 let DEPAIR = GEN_REWRITE_RULE TOP_SWEEP_CONV [PAIR_EQ] in
895 let prove_distinctness ax pat =
896 let f,args = strip_comb pat in
897 let rt = end_itlist (curry mk_pair) args in
898 let ty = mk_fun_ty (type_of pat) (type_of rt) in
899 let fn = genvar ty in
900 let dtm = mk_eq(mk_comb(fn,pat),rt) in
901 let eth = prove_recursive_functions_exist ax (list_mk_forall(args,dtm)) in
902 let args' = variants args args in
903 let atm = mk_eq(pat,list_mk_comb(f,args')) in
904 let ath = ASSUME atm in
905 let bth = AP_TERM fn ath in
906 let cth1 = SPECL args (ASSUME(snd(dest_exists(concl eth)))) in
907 let cth2 = INST (zip args' args) cth1 in
908 let pth = TRANS (TRANS (SYM cth1) bth) cth2 in
909 let qth = DEPAIR pth in
910 let qtm = concl qth in
911 let rth = rev_itlist (C(curry MK_COMB)) (CONJUNCTS(ASSUME qtm)) (REFL f) in
912 let tth = IMP_ANTISYM_RULE (DISCH atm qth) (DISCH qtm rth) in
913 let uth = GENL args (GENL args' tth) in
914 PROVE_HYP eth (SIMPLE_CHOOSE fn uth) in
916 let cls = conjuncts(snd(strip_exists(snd(strip_forall(concl ax))))) in
917 let pats = map (rand o lhand o snd o strip_forall) cls in
918 end_itlist CONJ (mapfilter (prove_distinctness ax) pats);;
920 let prove_constructors_distinct =
921 let num_ty = `:num` in
922 let rec allopairs f l m =
923 if l = [] then [] else
924 map (f (hd l)) (tl m) @ allopairs f (tl l) (tl m) in
925 let NEGATE = GEN_ALL o CONV_RULE (REWR_CONV (TAUT `a ==> F <=> ~a`)) in
926 let prove_distinct ax pat =
927 let nums = map mk_small_numeral (0--(length pat - 1)) in
928 let fn = genvar (mk_type("fun",[type_of(hd pat); num_ty])) in
929 let ls = map (curry mk_comb fn) pat in
930 let defs = map2 (fun l r -> list_mk_forall(frees (rand l),mk_eq(l,r)))
932 let eth = prove_recursive_functions_exist ax (list_mk_conj defs) in
933 let ev,bod = dest_exists(concl eth) in
934 let REWRITE = GEN_REWRITE_RULE ONCE_DEPTH_CONV (CONJUNCTS (ASSUME bod)) in
936 (fun t -> let f,args = if is_numeral t then t,[] else strip_comb t in
937 list_mk_comb(f,variants args args)) pat in
938 let pairs = allopairs (curry mk_eq) pat pat' in
939 let nths = map (REWRITE o AP_TERM fn o ASSUME) pairs in
940 let fths = map2 (fun t th -> NEGATE (DISCH t (CONV_RULE NUM_EQ_CONV th)))
942 CONJUNCTS(PROVE_HYP eth (SIMPLE_CHOOSE ev (end_itlist CONJ fths))) in
944 let cls = conjuncts(snd(strip_exists(snd(strip_forall(concl ax))))) in
945 let lefts = map (dest_comb o lhand o snd o strip_forall) cls in
946 let fns = itlist (insert o fst) lefts [] in
947 let pats = map (fun f -> map snd (filter ((=)f o fst) lefts)) fns in
949 (end_itlist (@) (mapfilter (prove_distinct ax) pats));;
951 (* ------------------------------------------------------------------------- *)
952 (* Automatically prove the case analysis theorems. *)
953 (* ------------------------------------------------------------------------- *)
955 let prove_cases_thm =
956 let mk_exclauses x rpats =
957 let xts = map (fun t -> list_mk_exists(frees t,mk_eq(x,t))) rpats in
958 mk_abs(x,list_mk_disj xts) in
960 let evs,bod = strip_exists tm in
961 let l,r = dest_eq bod in
962 if l = r then REFL l else
963 let lf,largs = strip_comb l
964 and rf,rargs = strip_comb r in
966 let ths = map (ASSUME o mk_eq) (zip rargs largs) in
967 let th1 = rev_itlist (C (curry MK_COMB)) ths (REFL lf) in
968 itlist EXISTS_EQUATION (map concl ths) (SYM th1)
969 else failwith "prove_triv" in
970 let rec prove_disj tm =
972 let l,r = dest_disj tm in
973 try DISJ1 (prove_triv l) r
974 with Failure _ -> DISJ2 l (prove_disj r)
977 let prove_eclause tm =
978 let avs,bod = strip_forall tm in
979 let ctm = if is_imp bod then rand bod else bod in
980 let cth = prove_disj ctm in
981 let dth = if is_imp bod then DISCH (lhand bod) cth else cth in
984 let avs,bod = strip_forall(concl th) in
985 let cls = map (snd o strip_forall) (conjuncts(lhand bod)) in
986 let pats = map (fun t -> if is_imp t then rand t else t) cls in
987 let spats = map dest_comb pats in
988 let preds = itlist (insert o fst) spats [] in
990 (fun pr -> map snd (filter (fun (p,x) -> p = pr) spats)) preds in
991 let xs = make_args "x" (freesl pats) (map (type_of o hd) rpatlist) in
992 let xpreds = map2 mk_exclauses xs rpatlist in
993 let ith = BETA_RULE (INST (zip xpreds preds) (SPEC_ALL th)) in
994 let eclauses = conjuncts(fst(dest_imp(concl ith))) in
995 MP ith (end_itlist CONJ (map prove_eclause eclauses));;
997 (* ------------------------------------------------------------------------- *)
998 (* Now deal with nested recursion. Need a store of previous theorems. *)
999 (* ------------------------------------------------------------------------- *)
1001 inductive_type_store :=
1002 ["list",(2,list_INDUCT,list_RECURSION);
1003 "option",(2,option_INDUCT,option_RECURSION);
1004 "sum",(2,sum_INDUCT,sum_RECURSION)] @
1005 (!inductive_type_store);;
1007 (* ------------------------------------------------------------------------- *)
1008 (* Also add a cached rewrite of distinctness and injectivity theorems. Since *)
1009 (* there can be quadratically many distinctness clauses, it would really be *)
1010 (* preferable to have a conversion, but this seems OK up 100 constructors. *)
1011 (* ------------------------------------------------------------------------- *)
1013 let basic_rectype_net = ref empty_net;;
1014 let distinctness_store = ref ["bool",TAUT `(T <=> F) <=> F`];;
1015 let injectivity_store = ref [];;
1017 let extend_rectype_net (tyname,(_,_,rth)) =
1018 let ths1 = try [prove_constructors_distinct rth] with Failure _ -> []
1019 and ths2 = try [prove_constructors_injective rth] with Failure _ -> [] in
1020 let canon_thl = itlist (mk_rewrites false) (ths1 @ ths2) [] in
1021 distinctness_store := map (fun th -> tyname,th) ths1 @ (!distinctness_store);
1022 injectivity_store := map (fun th -> tyname,th) ths2 @ (!injectivity_store);
1023 basic_rectype_net :=
1024 itlist (net_of_thm true) canon_thl (!basic_rectype_net);;
1026 do_list extend_rectype_net (!inductive_type_store);;
1028 (* ------------------------------------------------------------------------- *)
1029 (* Return distinctness and injectivity for a type by simple lookup. *)
1030 (* ------------------------------------------------------------------------- *)
1032 let distinctness ty = assoc ty (!distinctness_store);;
1034 let injectivity ty = assoc ty (!injectivity_store);;
1037 if ty = "num" then num_CASES else
1038 let _,ith,_ = assoc ty (!inductive_type_store) in prove_cases_thm ith;;
1040 (* ------------------------------------------------------------------------- *)
1041 (* Convenient definitions for type isomorphism. *)
1042 (* ------------------------------------------------------------------------- *)
1044 let ISO = new_definition
1045 `ISO (f:A->B) (g:B->A) <=> (!x. f(g x) = x) /\ (!y. g(f y) = y)`;;
1047 let ISO_REFL = prove
1048 (`ISO (\x:A. x) (\x. x)`,
1052 (`ISO (f:A->A') f' /\ ISO (g:B->B') g'
1053 ==> ISO (\h a'. g(h(f' a'))) (\h a. g'(h(f a)))`,
1054 REWRITE_TAC[ISO; FUN_EQ_THM] THEN MESON_TAC[]);;
1056 let ISO_USAGE = prove
1058 ==> (!P. (!x. P x) <=> (!x. P(g x))) /\
1059 (!P. (?x. P x) <=> (?x. P(g x))) /\
1060 (!a b. (a = g b) <=> (f a = b))`,
1061 REWRITE_TAC[ISO; FUN_EQ_THM] THEN MESON_TAC[]);;
1063 (* ------------------------------------------------------------------------- *)
1064 (* Hence extend type definition to nested types. *)
1065 (* ------------------------------------------------------------------------- *)
1067 let define_type_raw =
1069 (* ----------------------------------------------------------------------- *)
1070 (* Dispose of trivial antecedent. *)
1071 (* ----------------------------------------------------------------------- *)
1073 let TRIV_ANTE_RULE =
1074 let TRIV_IMP_CONV tm =
1075 let avs,bod = strip_forall tm in
1077 if is_eq bod then REFL (rand bod) else
1078 let ant,con = dest_imp bod in
1079 let ith = SUBS_CONV (CONJUNCTS(ASSUME ant)) (lhs con) in
1083 let tm = concl th in
1085 let ant,con = dest_imp(concl th) in
1086 let cjs = conjuncts ant in
1087 let cths = map TRIV_IMP_CONV cjs in
1088 MP th (end_itlist CONJ cths)
1091 (* ----------------------------------------------------------------------- *)
1092 (* Lift type bijections to "arbitrary" (well, free rec or function) type. *)
1093 (* ----------------------------------------------------------------------- *)
1095 let ISO_EXPAND_CONV = PURE_ONCE_REWRITE_CONV[ISO] in
1097 let rec lift_type_bijections iths cty =
1098 let itys = map (hd o snd o dest_type o type_of o lhand o concl) iths in
1099 try assoc cty (zip itys iths) with Failure _ ->
1100 if not (exists (C occurs_in cty) itys)
1101 then INST_TYPE [cty,aty] ISO_REFL else
1102 let tycon,isotys = dest_type cty in
1104 then MATCH_MP ISO_FUN
1105 (end_itlist CONJ (map (lift_type_bijections iths) isotys))
1107 ("lift_type_bijections: Unexpected type operator \""^tycon^"\"") in
1109 (* ----------------------------------------------------------------------- *)
1110 (* Prove isomorphism of nested types where former is the smaller. *)
1111 (* ----------------------------------------------------------------------- *)
1113 let DE_EXISTENTIALIZE_RULE =
1115 (`(?) P ==> (c = (@)P) ==> P c`,
1116 GEN_REWRITE_TAC (LAND_CONV o RAND_CONV) [GSYM ETA_AX] THEN
1117 DISCH_TAC THEN DISCH_THEN SUBST1_TAC THEN
1118 MATCH_MP_TAC SELECT_AX THEN POP_ASSUM ACCEPT_TAC) in
1119 let USE_PTH = MATCH_MP pth in
1120 let rec DE_EXISTENTIALIZE_RULE th =
1121 if not (is_exists(concl th)) then [],th else
1122 let th1 = USE_PTH th in
1123 let v1 = rand(rand(concl th1)) in
1124 let gv = genvar(type_of v1) in
1125 let th2 = CONV_RULE BETA_CONV (UNDISCH (INST [gv,v1] th1)) in
1126 let vs,th3 = DE_EXISTENTIALIZE_RULE th2 in
1128 DE_EXISTENTIALIZE_RULE in
1130 let grab_type = type_of o rand o lhand o snd o strip_forall in
1132 let clause_corresponds cl0 =
1133 let f0,ctm0 = dest_comb (lhs cl0) in
1134 let c0 = fst(dest_const(fst(strip_comb ctm0))) in
1135 let dty0,rty0 = dest_fun_ty (type_of f0) in
1137 let f1,ctm1 = dest_comb (lhs cl1) in
1138 let c1 = fst(dest_const(fst(strip_comb ctm1))) in
1139 let dty1,rty1 = dest_fun_ty (type_of f1) in
1140 c0 = c1 & dty0 = rty1 & rty0 = dty1 in
1142 let prove_inductive_types_isomorphic n k (ith0,rth0) (ith1,rth1) =
1143 let sth0 = SPEC_ALL rth0
1144 and sth1 = SPEC_ALL rth1
1145 and t_tm = concl TRUTH in
1146 let pevs0,pbod0 = strip_exists (concl sth0)
1147 and pevs1,pbod1 = strip_exists (concl sth1) in
1148 let pcjs0,qcjs0 = chop_list k (conjuncts pbod0)
1149 and pcjs1,qcjs1 = chop_list k (snd(chop_list n (conjuncts pbod1))) in
1150 let tyal0 = setify (zip (map grab_type pcjs1) (map grab_type pcjs0)) in
1151 let tyal1 = map (fun (a,b) -> (b,a)) tyal0 in
1153 (fun f -> let domty,ranty = dest_fun_ty (type_of f) in
1154 tysubst tyal0 domty,ranty) pevs0
1156 (fun f -> let domty,ranty = dest_fun_ty (type_of f) in
1157 tysubst tyal1 domty,ranty) pevs1 in
1158 let tth0 = INST_TYPE tyins0 sth0
1159 and tth1 = INST_TYPE tyins1 sth1 in
1160 let evs0,bod0 = strip_exists(concl tth0)
1161 and evs1,bod1 = strip_exists(concl tth1) in
1162 let lcjs0,rcjs0 = chop_list k (map (snd o strip_forall) (conjuncts bod0))
1163 and lcjs1,rcjsx = chop_list k (map (snd o strip_forall)
1164 (snd(chop_list n (conjuncts bod1)))) in
1165 let rcjs1 = map (fun t -> find (clause_corresponds t) rcjsx) rcjs0 in
1166 let proc_clause tm0 tm1 =
1167 let l0,r0 = dest_eq tm0
1168 and l1,r1 = dest_eq tm1 in
1169 let vc0,wargs0 = strip_comb r0 in
1170 let con0,vargs0 = strip_comb(rand l0) in
1171 let gargs0 = map (genvar o type_of) wargs0 in
1172 let nestf0 = map (fun a -> can (find (fun t -> is_comb t & rand t = a))
1174 let targs0 = map2 (fun a f ->
1175 if f then find (fun t -> is_comb t & rand t = a) wargs0 else a)
1177 let gvlist0 = zip wargs0 gargs0 in
1178 let xargs = map (fun v -> assoc v gvlist0) targs0 in
1180 list_mk_abs(gargs0,list_mk_comb(fst(strip_comb(rand l1)),xargs)),vc0 in
1181 let vc1,wargs1 = strip_comb r1 in
1182 let con1,vargs1 = strip_comb(rand l1) in
1183 let gargs1 = map (genvar o type_of) wargs1 in
1185 (fun a f -> if f then
1186 find (fun t -> is_comb t & rand t = a) wargs1
1187 else a) vargs1 nestf0 in
1188 let gvlist1 = zip wargs1 gargs1 in
1189 let xargs = map (fun v -> assoc v gvlist1) targs1 in
1191 list_mk_abs(gargs1,list_mk_comb(fst(strip_comb(rand l0)),xargs)),vc1 in
1193 let insts0,insts1 = unzip (map2 proc_clause (lcjs0@rcjs0) (lcjs1@rcjs1)) in
1194 let uth0 = BETA_RULE(INST insts0 tth0)
1195 and uth1 = BETA_RULE(INST insts1 tth1) in
1196 let efvs0,sth0 = DE_EXISTENTIALIZE_RULE uth0
1197 and efvs1,sth1 = DE_EXISTENTIALIZE_RULE uth1 in
1199 (fun t1 -> find (fun t2 -> hd(tl(snd(dest_type(type_of t1)))) =
1200 hd(snd(dest_type(type_of t2)))) efvs1) efvs0 in
1201 let isotms = map2 (fun ff gg -> list_mk_icomb "ISO" [ff;gg]) efvs0 efvs2 in
1202 let ctm = list_mk_conj isotms in
1203 let cth1 = ISO_EXPAND_CONV ctm in
1204 let ctm1 = rand(concl cth1) in
1205 let cjs = conjuncts ctm1 in
1206 let eee = map (fun n -> n mod 2 = 0) (0--(length cjs - 1)) in
1207 let cjs1,cjs2 = partition fst (zip eee cjs) in
1208 let ctm2 = mk_conj(list_mk_conj (map snd cjs1),
1209 list_mk_conj (map snd cjs2)) in
1210 let DETRIV_RULE = TRIV_ANTE_RULE o REWRITE_RULE[sth0;sth1] in
1212 let itha = SPEC_ALL ith0 in
1213 let icjs = conjuncts(rand(concl itha)) in
1215 (fun tm -> tryfind (fun vtm -> term_match [] vtm tm) icjs)
1216 (conjuncts (rand ctm2)) in
1217 let tvs = subtract (fst(strip_forall(concl ith0)))
1218 (itlist (fun (_,x,_) -> union (map snd x)) cinsts []) in
1220 map (fun p -> let x = mk_var("x",hd(snd(dest_type(type_of p)))) in
1221 mk_abs(x,t_tm),p) tvs in
1222 DETRIV_RULE (INST ctvs (itlist INSTANTIATE cinsts itha))
1224 let itha = SPEC_ALL ith1 in
1225 let icjs = conjuncts(rand(concl itha)) in
1227 (fun tm -> tryfind (fun vtm -> term_match [] vtm tm) icjs)
1228 (conjuncts (lhand ctm2)) in
1229 let tvs = subtract (fst(strip_forall(concl ith1)))
1230 (itlist (fun (_,x,_) -> union (map snd x)) cinsts []) in
1232 map (fun p -> let x = mk_var("x",hd(snd(dest_type(type_of p)))) in
1233 mk_abs(x,t_tm),p) tvs in
1234 DETRIV_RULE (INST ctvs (itlist INSTANTIATE cinsts itha)) in
1235 let cths4 = map2 CONJ (CONJUNCTS jth0) (CONJUNCTS jth1) in
1236 let cths5 = map (PURE_ONCE_REWRITE_RULE[GSYM ISO]) cths4 in
1237 let cth6 = end_itlist CONJ cths5 in
1238 cth6,CONJ sth0 sth1 in
1240 (* ----------------------------------------------------------------------- *)
1241 (* Define nested type by doing a 1-level unwinding. *)
1242 (* ----------------------------------------------------------------------- *)
1244 let SCRUB_ASSUMPTION th =
1245 let hyps = hyp th in
1246 let eqn = find (fun t -> let x = lhs t in
1247 forall (fun u -> not (free_in x (rand u))) hyps)
1249 let l,r = dest_eq eqn in
1250 MP (INST [r,l] (DISCH eqn th)) (REFL r) in
1252 let define_type_basecase def =
1253 let add_id s = fst(dest_var(genvar bool_ty)) in
1254 let def' = map (I F_F (map (add_id F_F I))) def in
1255 define_type_raw def' in
1257 let SIMPLE_BETA_RULE = GSYM o PURE_REWRITE_RULE[BETA_THM; FUN_EQ_THM] in
1258 let ISO_USAGE_RULE = MATCH_MP ISO_USAGE in
1259 let SIMPLE_ISO_EXPAND_RULE = CONV_RULE(REWR_CONV ISO) in
1261 let REWRITE_FUN_EQ_RULE =
1262 let ths = itlist (mk_rewrites false) [FUN_EQ_THM] [] in
1263 let net = itlist (net_of_thm false) ths (basic_net()) in
1264 CONV_RULE o GENERAL_REWRITE_CONV true TOP_DEPTH_CONV net in
1266 let is_nested vs ty =
1267 not (is_vartype ty) & not (intersect (tyvars ty) vs = []) in
1268 let rec modify_type alist ty =
1269 try rev_assoc ty alist
1270 with Failure _ -> try
1271 let tycon,tyargs = dest_type ty in
1272 mk_type(tycon,map (modify_type alist) tyargs)
1273 with Failure _ -> ty in
1274 let modify_item alist (s,l) =
1275 s,map (modify_type alist) l in
1276 let modify_clause alist (l,lis) =
1277 l,map (modify_item alist) lis in
1278 let recover_clause id tm =
1279 let con,args = strip_comb tm in
1280 fst(dest_const con)^id,map type_of args in
1281 let rec create_auxiliary_clauses nty =
1282 let id = fst(dest_var(genvar bool_ty)) in
1283 let tycon,tyargs = dest_type nty in
1284 let k,ith,rth = try assoc tycon (!inductive_type_store) with Failure _ ->
1285 failwith ("Can't find definition for nested type: "^tycon) in
1286 let evs,bod = strip_exists(snd(strip_forall(concl rth))) in
1287 let cjs = map (lhand o snd o strip_forall) (conjuncts bod) in
1288 let rtys = map (hd o snd o dest_type o type_of) evs in
1289 let tyins = tryfind (fun vty -> type_match vty nty []) rtys in
1290 let cjs' = map (inst tyins o rand) (fst(chop_list k cjs)) in
1291 let mtys = itlist (insert o type_of) cjs' [] in
1292 let pcons = map (fun ty -> filter (fun t -> type_of t = ty) cjs') mtys in
1293 let cls' = zip mtys (map (map (recover_clause id)) pcons) in
1294 let tyal = map (fun ty -> mk_vartype(fst(dest_type ty)^id),ty) mtys in
1295 let cls'' = map (modify_type tyal F_F map (modify_item tyal)) cls' in
1296 k,tyal,cls'',INST_TYPE tyins ith,INST_TYPE tyins rth in
1297 let rec define_type_nested def =
1298 let n = length(itlist (@) (map (map fst o snd) def) []) in
1299 let newtys = map fst def in
1300 let utys = unions (itlist (union o map snd o snd) def []) in
1301 let rectys = filter (is_nested newtys) utys in
1303 let th1,th2 = define_type_basecase def in n,th1,th2 else
1304 let nty = hd (sort (fun t1 t2 -> occurs_in t2 t1) rectys) in
1305 let k,tyal,ncls,ith,rth = create_auxiliary_clauses nty in
1306 let cls = map (modify_clause tyal) def @ ncls in
1307 let _,ith1,rth1 = define_type_nested cls in
1308 let xnewtys = map (hd o snd o dest_type o type_of)
1309 (fst(strip_exists(snd(strip_forall(concl rth1))))) in
1310 let xtyal = map (fun ty -> let s = dest_vartype ty in
1311 find (fun t -> fst(dest_type t) = s) xnewtys,ty)
1313 let ith0 = INST_TYPE xtyal ith
1314 and rth0 = INST_TYPE xtyal rth in
1315 let isoth,rclauses =
1316 prove_inductive_types_isomorphic n k (ith0,rth0) (ith1,rth1) in
1317 let irth3 = CONJ ith1 rth1 in
1318 let vtylist = itlist (insert o type_of) (variables(concl irth3)) [] in
1319 let isoths = CONJUNCTS isoth in
1320 let isotys = map (hd o snd o dest_type o type_of o lhand o concl) isoths in
1321 let ctylist = filter
1322 (fun ty -> exists (fun t -> occurs_in t ty) isotys) vtylist in
1323 let atylist = itlist
1324 (union o striplist dest_fun_ty) ctylist [] in
1325 let isoths' = map (lift_type_bijections isoths)
1326 (filter (fun ty -> exists (fun t -> occurs_in t ty) isotys) atylist) in
1327 let cisoths = map (BETA_RULE o lift_type_bijections isoths')
1329 let uisoths = map ISO_USAGE_RULE cisoths in
1330 let visoths = map (ASSUME o concl) uisoths in
1331 let irth4 = itlist PROVE_HYP uisoths (REWRITE_FUN_EQ_RULE visoths irth3) in
1332 let irth5 = REWRITE_RULE
1333 (rclauses :: map SIMPLE_ISO_EXPAND_RULE isoths') irth4 in
1334 let irth6 = repeat SCRUB_ASSUMPTION irth5 in
1335 let ncjs = filter (fun t -> exists (fun v -> not(is_var v))
1336 (snd(strip_comb(rand(lhs(snd(strip_forall t)))))))
1337 (conjuncts(snd(strip_exists
1338 (snd(strip_forall(rand(concl irth6))))))) in
1340 let vs,bod = strip_forall tm in
1341 let rdeb = rand(lhs bod) in
1342 let rdef = list_mk_abs(vs,rdeb) in
1343 let newname = fst(dest_var(genvar bool_ty)) in
1344 let def = mk_eq(mk_var(newname,type_of rdef),rdef) in
1345 let dth = new_definition def in
1346 SIMPLE_BETA_RULE dth in
1347 let dths = map mk_newcon ncjs in
1348 let ith6,rth6 = CONJ_PAIR(PURE_REWRITE_RULE dths irth6) in
1351 let newtys = map fst def in
1352 let truecons = itlist (@) (map (map fst o snd) def) [] in
1353 let (p,ith0,rth0) = define_type_nested def in
1354 let avs,etm = strip_forall(concl rth0) in
1355 let allcls = conjuncts(snd(strip_exists etm)) in
1356 let relcls = fst(chop_list (length truecons) allcls) in
1358 map (repeat rator o rand o lhand o snd o strip_forall) relcls in
1360 map2 (fun s r -> SYM(new_definition (mk_eq(mk_var(s,type_of r),r))))
1362 let tavs = make_args "f" [] (map type_of avs) in
1363 let ith1 = SUBS cdefs ith0
1364 and rth1 = GENL tavs (SUBS cdefs (SPECL tavs rth0)) in
1365 let retval = p,ith1,rth1 in
1366 let newentries = map (fun s -> dest_vartype s,retval) newtys in
1367 (inductive_type_store := newentries @ (!inductive_type_store);
1368 do_list extend_rectype_net newentries; ith1,rth1);;
1370 (* ----------------------------------------------------------------------- *)
1371 (* The overall function, with rather crude string-based benignity. *)
1372 (* ----------------------------------------------------------------------- *)
1374 let the_inductive_types = ref
1375 ["list = NIL | CONS A list",(list_INDUCT,list_RECURSION);
1376 "option = NONE | SOME A",(option_INDUCT,option_RECURSION);
1377 "sum = INL A | INR B",(sum_INDUCT,sum_RECURSION)];;
1380 try let retval = assoc s (!the_inductive_types) in
1381 (warn true "Benign redefinition of inductive type"; retval)
1383 let defspec = parse_inductive_type_specification s in
1384 let newtypes = map fst defspec
1385 and constructors = itlist ((@) o map fst) (map snd defspec) [] in
1386 if not(length(setify newtypes) = length newtypes)
1387 then failwith "define_type: multiple definitions of a type"
1388 else if not(length(setify constructors) = length constructors)
1389 then failwith "define_type: multiple instances of a constructor"
1390 else if exists (can get_type_arity o dest_vartype) newtypes
1391 then let t = find (can get_type_arity) (map dest_vartype newtypes) in
1392 failwith("define_type: type :"^t^" already defined")
1393 else if exists (can get_const_type) constructors
1394 then let t = find (can get_const_type) constructors in
1395 failwith("define_type: constant "^t^" already defined")
1397 let retval = define_type_raw defspec in
1398 the_inductive_types := (s,retval)::(!the_inductive_types); retval;;
1400 (* ------------------------------------------------------------------------- *)
1401 (* Unwinding, and application of patterns. Add easy cases to default net. *)
1402 (* ------------------------------------------------------------------------- *)
1404 let UNWIND_CONV,MATCH_CONV =
1406 (`(if ?!x. x = a /\ p then @x. x = a /\ p else @x. F) =
1407 (if p then a else @x. F)`,
1408 BOOL_CASES_TAC `p:bool` THEN ASM_REWRITE_TAC[COND_ID] THEN
1411 (`_MATCH x (_SEQPATTERN r s) =
1412 (if ?y. r x y then _MATCH x r else _MATCH x s) /\
1413 _FUNCTION (_SEQPATTERN r s) x =
1414 (if ?y. r x y then _FUNCTION r x else _FUNCTION s x)`,
1415 REWRITE_TAC[_MATCH; _SEQPATTERN; _FUNCTION] THEN
1418 (`((?y. _UNGUARDED_PATTERN (GEQ s t) (GEQ u y)) <=> s = t) /\
1419 ((?y. _GUARDED_PATTERN (GEQ s t) p (GEQ u y)) <=> s = t /\ p)`,
1420 REWRITE_TAC[_UNGUARDED_PATTERN; _GUARDED_PATTERN; GEQ_DEF] THEN
1423 (`(_MATCH x (\y z. P y z) = if ?!z. P x z then @z. P x z else @x. F) /\
1424 (_FUNCTION (\y z. P y z) x = if ?!z. P x z then @z. P x z else @x. F)`,
1425 REWRITE_TAC[_MATCH; _FUNCTION])
1427 (`(_UNGUARDED_PATTERN (GEQ s t) (GEQ u y) <=> y = u /\ s = t) /\
1428 (_GUARDED_PATTERN (GEQ s t) p (GEQ u y) <=> y = u /\ s = t /\ p)`,
1429 REWRITE_TAC[_UNGUARDED_PATTERN; _GUARDED_PATTERN; GEQ_DEF] THEN
1432 (`(if ?!z. z = k then @z. z = k else @x. F) = k`,
1434 let rec INSIDE_EXISTS_CONV conv tm =
1435 if is_exists tm then BINDER_CONV (INSIDE_EXISTS_CONV conv) tm
1437 let PUSH_EXISTS_CONV =
1438 let econv = REWR_CONV SWAP_EXISTS_THM in
1439 let rec conv bc tm =
1440 try (econv THENC BINDER_CONV(conv bc)) tm
1441 with Failure _ -> bc tm in
1443 let BREAK_CONS_CONV =
1444 let conv2 = GEN_REWRITE_CONV DEPTH_CONV [AND_CLAUSES; OR_CLAUSES] THENC
1445 ASSOC_CONV CONJ_ASSOC in
1447 let conv0 = TOP_SWEEP_CONV(REWRITES_CONV(!basic_rectype_net)) in
1448 let conv1 = if is_conj tm then LAND_CONV conv0 else conv0 in
1449 (conv1 THENC conv2) tm in
1451 let baseconv = GEN_REWRITE_CONV I
1452 [UNWIND_THM1; UNWIND_THM2;
1453 EQT_INTRO(SPEC_ALL EXISTS_REFL);
1454 EQT_INTRO(GSYM(SPEC_ALL EXISTS_REFL))] in
1455 let rec UNWIND_CONV tm =
1456 let evs,bod = strip_exists tm in
1457 let eqs = conjuncts bod in
1459 (fun tm -> is_eq tm &
1460 let l,r = dest_eq tm in
1461 (mem l evs & not (free_in l r)) or
1462 (mem r evs & not (free_in r l))) eqs in
1463 let l,r = dest_eq eq in
1464 let v = if mem l evs & not (free_in l r) then l else r in
1465 let cjs' = eq::(subtract eqs [eq]) in
1466 let n = length evs - (1 + index v (rev evs)) in
1467 let th1 = CONJ_ACI_RULE(mk_eq(bod,list_mk_conj cjs')) in
1468 let th2 = itlist MK_EXISTS evs th1 in
1469 let th3 = funpow n BINDER_CONV (PUSH_EXISTS_CONV baseconv)
1470 (rand(concl th2)) in
1471 CONV_RULE (RAND_CONV UNWIND_CONV) (TRANS th2 th3)
1472 with Failure _ -> REFL tm in
1474 let MATCH_SEQPATTERN_CONV =
1475 GEN_REWRITE_CONV I [pth_1] THENC
1476 RATOR_CONV(LAND_CONV
1477 (BINDER_CONV(RATOR_CONV BETA_CONV THENC BETA_CONV) THENC
1478 PUSH_EXISTS_CONV(GEN_REWRITE_CONV I [pth_2] THENC BREAK_CONS_CONV) THENC
1480 GEN_REWRITE_CONV DEPTH_CONV
1481 [EQT_INTRO(SPEC_ALL EQ_REFL); AND_CLAUSES] THENC
1482 GEN_REWRITE_CONV DEPTH_CONV [EXISTS_SIMP]))
1483 and MATCH_ONEPATTERN_CONV tm =
1484 let th1 = GEN_REWRITE_CONV I [pth_3] tm in
1485 let tm' = body(rand(lhand(rand(concl th1)))) in
1486 let th2 = (INSIDE_EXISTS_CONV
1487 (GEN_REWRITE_CONV I [pth_4] THENC
1488 RAND_CONV BREAK_CONS_CONV) THENC
1490 GEN_REWRITE_CONV DEPTH_CONV
1491 [EQT_INTRO(SPEC_ALL EQ_REFL); AND_CLAUSES] THENC
1492 GEN_REWRITE_CONV DEPTH_CONV [EXISTS_SIMP])
1494 let conv tm = if tm = lhand(concl th2) then th2 else fail() in
1496 (RAND_CONV (RATOR_CONV
1497 (COMB2_CONV (RAND_CONV (BINDER_CONV conv)) (BINDER_CONV conv))))
1499 let MATCH_SEQPATTERN_CONV_TRIV =
1500 MATCH_SEQPATTERN_CONV THENC
1501 GEN_REWRITE_CONV I [COND_CLAUSES]
1502 and MATCH_SEQPATTERN_CONV_GEN =
1503 MATCH_SEQPATTERN_CONV THENC
1504 GEN_REWRITE_CONV TRY_CONV [COND_CLAUSES]
1505 and MATCH_ONEPATTERN_CONV_TRIV =
1506 MATCH_ONEPATTERN_CONV THENC
1507 GEN_REWRITE_CONV I [pth_5]
1508 and MATCH_ONEPATTERN_CONV_GEN =
1509 MATCH_ONEPATTERN_CONV THENC
1510 GEN_REWRITE_CONV TRY_CONV [pth_0; pth_5] in
1511 do_list extend_basic_convs
1512 ["MATCH_SEQPATTERN_CONV",
1513 (`_MATCH x (_SEQPATTERN r s)`,MATCH_SEQPATTERN_CONV_TRIV);
1514 "FUN_SEQPATTERN_CONV",
1515 (`_FUNCTION (_SEQPATTERN r s) x`,MATCH_SEQPATTERN_CONV_TRIV);
1516 "MATCH_ONEPATTERN_CONV",
1517 (`_MATCH x (\y z. P y z)`,MATCH_ONEPATTERN_CONV_TRIV);
1518 "FUN_ONEPATTERN_CONV",
1519 (`_FUNCTION (\y z. P y z) x`,MATCH_ONEPATTERN_CONV_TRIV)];
1520 (CHANGED_CONV UNWIND_CONV,
1521 (MATCH_SEQPATTERN_CONV_GEN ORELSEC MATCH_ONEPATTERN_CONV_GEN));;
1523 let FORALL_UNWIND_CONV =
1524 let PUSH_FORALL_CONV =
1525 let econv = REWR_CONV SWAP_FORALL_THM in
1526 let rec conv bc tm =
1527 try (econv THENC BINDER_CONV(conv bc)) tm
1528 with Failure _ -> bc tm in
1530 let baseconv = GEN_REWRITE_CONV I
1531 [MESON[] `(!x. x = a /\ p x ==> q x) <=> (p a ==> q a)`;
1532 MESON[] `(!x. a = x /\ p x ==> q x) <=> (p a ==> q a)`;
1533 MESON[] `(!x. x = a ==> q x) <=> q a`;
1534 MESON[] `(!x. a = x ==> q x) <=> q a`] in
1535 let rec FORALL_UNWIND_CONV tm =
1536 try let avs,bod = strip_forall tm in
1537 let ant,con = dest_imp bod in
1538 let eqs = conjuncts ant in
1539 let eq = find (fun tm ->
1541 let l,r = dest_eq tm in
1542 (mem l avs & not (free_in l r)) or
1543 (mem r avs & not (free_in r l))) eqs in
1544 let l,r = dest_eq eq in
1545 let v = if mem l avs & not (free_in l r) then l else r in
1546 let cjs' = eq::(subtract eqs [eq]) in
1547 let n = length avs - (1 + index v (rev avs)) in
1548 let th1 = CONJ_ACI_RULE(mk_eq(ant,list_mk_conj cjs')) in
1549 let th2 = AP_THM (AP_TERM (rator(rator bod)) th1) con in
1550 let th3 = itlist MK_FORALL avs th2 in
1551 let th4 = funpow n BINDER_CONV (PUSH_FORALL_CONV baseconv)
1552 (rand(concl th3)) in
1553 CONV_RULE (RAND_CONV FORALL_UNWIND_CONV) (TRANS th3 th4)
1554 with Failure _ -> REFL tm in
1555 FORALL_UNWIND_CONV;;