1 (* ========================================================================= *)
2 (* Reasonably efficient conversions for various canonical forms. *)
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 (* Pre-simplification. *)
14 (* ------------------------------------------------------------------------- *)
17 GEN_REWRITE_CONV TOP_DEPTH_CONV
18 [NOT_CLAUSES; AND_CLAUSES; OR_CLAUSES; IMP_CLAUSES; EQ_CLAUSES;
19 FORALL_SIMP; EXISTS_SIMP; EXISTS_OR_THM; FORALL_AND_THM;
20 LEFT_EXISTS_AND_THM; RIGHT_EXISTS_AND_THM;
21 LEFT_FORALL_OR_THM; RIGHT_FORALL_OR_THM];;
23 (* ------------------------------------------------------------------------- *)
24 (* ACI rearrangements of conjunctions and disjunctions. This is much faster *)
25 (* than AC xxx_ACI on large problems, as well as being more controlled. *)
26 (* ------------------------------------------------------------------------- *)
29 let rec mk_fun th fn =
32 let th1,th2 = CONJ_PAIR th in
33 mk_fun th1 (mk_fun th2 fn)
37 let l,r = dest_conj tm in CONJ (use_fun fn l) (use_fun fn r)
40 let p,p' = dest_eq fm in
41 if p = p' then REFL p else
42 let th = use_fun (mk_fun (ASSUME p) undefined) p'
43 and th' = use_fun (mk_fun (ASSUME p') undefined) p in
44 IMP_ANTISYM_RULE (DISCH_ALL th) (DISCH_ALL th');;
47 let pth_left = UNDISCH(TAUT `~(a \/ b) ==> ~a`)
48 and pth_right = UNDISCH(TAUT `~(a \/ b) ==> ~b`)
49 and pth = repeat UNDISCH (TAUT `~a ==> ~b ==> ~(a \/ b)`)
50 and pth_neg = UNDISCH(TAUT `(~a <=> ~b) ==> (a <=> b)`)
51 and a_tm = `a:bool` and b_tm = `b:bool` in
52 let NOT_DISJ_PAIR th =
53 let p,q = dest_disj(rand(concl th)) in
54 let ilist = [p,a_tm; q,b_tm] in
55 PROVE_HYP th (INST ilist pth_left),
56 PROVE_HYP th (INST ilist pth_right)
57 and NOT_DISJ th1 th2 =
58 let th3 = INST [rand(concl th1),a_tm; rand(concl th2),b_tm] pth in
59 PROVE_HYP th1 (PROVE_HYP th2 th3) in
60 let rec mk_fun th fn =
61 let tm = rand(concl th) in
63 let th1,th2 = NOT_DISJ_PAIR th in
64 mk_fun th1 (mk_fun th2 fn)
68 let l,r = dest_disj tm in NOT_DISJ (use_fun fn l) (use_fun fn r)
71 let p,p' = dest_eq fm in
72 if p = p' then REFL p else
73 let th = use_fun (mk_fun (ASSUME(mk_neg p)) undefined) p'
74 and th' = use_fun (mk_fun (ASSUME(mk_neg p')) undefined) p in
75 let th1 = IMP_ANTISYM_RULE (DISCH_ALL th) (DISCH_ALL th') in
76 PROVE_HYP th1 (INST [p,a_tm; p',b_tm] pth_neg);;
78 (* ------------------------------------------------------------------------- *)
79 (* Order canonically, right-associate and remove duplicates. *)
80 (* ------------------------------------------------------------------------- *)
82 let CONJ_CANON_CONV tm =
83 let tm' = list_mk_conj(setify(conjuncts tm)) in
84 CONJ_ACI_RULE(mk_eq(tm,tm'));;
86 let DISJ_CANON_CONV tm =
87 let tm' = list_mk_disj(setify(disjuncts tm)) in
88 DISJ_ACI_RULE(mk_eq(tm,tm'));;
90 (* ------------------------------------------------------------------------- *)
91 (* General NNF conversion. The user supplies some conversion to be applied *)
92 (* to atomic formulas. *)
94 (* "Iff"s are split conjunctively or disjunctively according to the flag *)
95 (* argument (conjuctively = true) until a universal quantifier (modulo *)
96 (* current parity) is passed; after that they are split conjunctively. This *)
97 (* is appropriate when the result is passed to a disjunctive splitter *)
98 (* followed by a clausal form inner core, such as MESON. *)
100 (* To avoid some duplicate computation, this function will in general *)
101 (* enter a recursion where it simultaneously computes NNF representations *)
102 (* for "p" and "~p", so the user needs to supply an atomic "conversion" *)
103 (* that does the same. *)
104 (* ------------------------------------------------------------------------- *)
106 let (GEN_NNF_CONV:bool->conv*(term->thm*thm)->conv) =
107 let and_tm = `(/\)` and or_tm = `(\/)` and not_tm = `(~)`
108 and pth_not_not = TAUT `~ ~ p = p`
109 and pth_not_and = TAUT `~(p /\ q) <=> ~p \/ ~q`
110 and pth_not_or = TAUT `~(p \/ q) <=> ~p /\ ~q`
111 and pth_imp = TAUT `p ==> q <=> ~p \/ q`
112 and pth_not_imp = TAUT `~(p ==> q) <=> p /\ ~q`
113 and pth_eq = TAUT `(p <=> q) <=> p /\ q \/ ~p /\ ~q`
114 and pth_not_eq = TAUT `~(p <=> q) <=> p /\ ~q \/ ~p /\ q`
115 and pth_eq' = TAUT `(p <=> q) <=> (p \/ ~q) /\ (~p \/ q)`
116 and pth_not_eq' = TAUT `~(p <=> q) <=> (p \/ q) /\ (~p \/ ~q)`
117 and [pth_not_forall; pth_not_exists; pth_not_exu] =
119 (`(~((!) P) <=> ?x:A. ~(P x)) /\
120 (~((?) P) <=> !x:A. ~(P x)) /\
121 (~((?!) P) <=> (!x:A. ~(P x)) \/ ?x y. P x /\ P y /\ ~(y = x))`,
123 GEN_REWRITE_TAC (LAND_CONV o funpow 2 RAND_CONV) [GSYM ETA_AX] THEN
124 REWRITE_TAC[NOT_EXISTS_THM; NOT_FORALL_THM; EXISTS_UNIQUE_DEF;
125 DE_MORGAN_THM; NOT_IMP] THEN
126 REWRITE_TAC[CONJ_ASSOC; EQ_SYM_EQ])
128 (`((?!) P) <=> (?x:A. P x) /\ !x y. ~(P x) \/ ~(P y) \/ (y = x)`,
129 GEN_REWRITE_TAC (LAND_CONV o RAND_CONV) [GSYM ETA_AX] THEN
130 REWRITE_TAC[EXISTS_UNIQUE_DEF; TAUT `a /\ b ==> c <=> ~a \/ ~b \/ c`] THEN
131 REWRITE_TAC[EQ_SYM_EQ])
132 and p_tm = `p:bool` and q_tm = `q:bool` in
133 let rec NNF_DCONV cf baseconvs tm =
135 Comb(Comb(Const("/\\",_),l),r) ->
136 let th_lp,th_ln = NNF_DCONV cf baseconvs l
137 and th_rp,th_rn = NNF_DCONV cf baseconvs r in
138 MK_COMB(AP_TERM and_tm th_lp,th_rp),
139 TRANS (INST [l,p_tm; r,q_tm] pth_not_and)
140 (MK_COMB(AP_TERM or_tm th_ln,th_rn))
141 | Comb(Comb(Const("\\/",_),l),r) ->
142 let th_lp,th_ln = NNF_DCONV cf baseconvs l
143 and th_rp,th_rn = NNF_DCONV cf baseconvs r in
144 MK_COMB(AP_TERM or_tm th_lp,th_rp),
145 TRANS (INST [l,p_tm; r,q_tm] pth_not_or)
146 (MK_COMB(AP_TERM and_tm th_ln,th_rn))
147 | Comb(Comb(Const("==>",_),l),r) ->
148 let th_lp,th_ln = NNF_DCONV cf baseconvs l
149 and th_rp,th_rn = NNF_DCONV cf baseconvs r in
150 TRANS (INST [l,p_tm; r,q_tm] pth_imp)
151 (MK_COMB(AP_TERM or_tm th_ln,th_rp)),
152 TRANS (INST [l,p_tm; r,q_tm] pth_not_imp)
153 (MK_COMB(AP_TERM and_tm th_lp,th_rn))
154 | Comb(Comb(Const("=",Tyapp("fun",Tyapp("bool",_)::_)),l),r) ->
155 let th_lp,th_ln = NNF_DCONV cf baseconvs l
156 and th_rp,th_rn = NNF_DCONV cf baseconvs r in
158 TRANS (INST [l,p_tm; r,q_tm] pth_eq')
159 (MK_COMB(AP_TERM and_tm (MK_COMB(AP_TERM or_tm th_lp,th_rn)),
160 MK_COMB(AP_TERM or_tm th_ln,th_rp))),
161 TRANS (INST [l,p_tm; r,q_tm] pth_not_eq')
162 (MK_COMB(AP_TERM and_tm (MK_COMB(AP_TERM or_tm th_lp,th_rp)),
163 MK_COMB(AP_TERM or_tm th_ln,th_rn)))
165 TRANS (INST [l,p_tm; r,q_tm] pth_eq)
166 (MK_COMB(AP_TERM or_tm (MK_COMB(AP_TERM and_tm th_lp,th_rp)),
167 MK_COMB(AP_TERM and_tm th_ln,th_rn))),
168 TRANS (INST [l,p_tm; r,q_tm] pth_not_eq)
169 (MK_COMB(AP_TERM or_tm (MK_COMB(AP_TERM and_tm th_lp,th_rn)),
170 MK_COMB(AP_TERM and_tm th_ln,th_rp)))
171 | Comb(Const("!",Tyapp("fun",Tyapp("fun",ty::_)::_)) as q,
172 (Abs(x,t) as bod)) ->
173 let th_p,th_n = NNF_DCONV true baseconvs t in
174 AP_TERM q (ABS x th_p),
175 let th1 = INST [bod,mk_var("P",mk_fun_ty ty bool_ty)]
176 (INST_TYPE [ty,aty] pth_not_forall)
177 and th2 = TRANS (AP_TERM not_tm (BETA(mk_comb(bod,x)))) th_n in
178 TRANS th1 (MK_EXISTS x th2)
179 | Comb(Const("?",Tyapp("fun",Tyapp("fun",ty::_)::_)) as q,
180 (Abs(x,t) as bod)) ->
181 let th_p,th_n = NNF_DCONV cf baseconvs t in
182 AP_TERM q (ABS x th_p),
183 let th1 = INST [bod,mk_var("P",mk_fun_ty ty bool_ty)]
184 (INST_TYPE [ty,aty] pth_not_exists)
185 and th2 = TRANS (AP_TERM not_tm (BETA(mk_comb(bod,x)))) th_n in
186 TRANS th1 (MK_FORALL x th2)
187 | Comb(Const("?!",Tyapp("fun",Tyapp("fun",ty::_)::_)),
188 (Abs(x,t) as bod)) ->
189 let y = variant (x::frees t) x
190 and th_p,th_n = NNF_DCONV cf baseconvs t in
191 let eq = mk_eq(y,x) in
192 let eth_p,eth_n = baseconvs eq
193 and bth = BETA (mk_comb(bod,x))
194 and bth' = BETA_CONV(mk_comb(bod,y)) in
195 let th_p' = INST [y,x] th_p and th_n' = INST [y,x] th_n in
196 let th1 = INST [bod,mk_var("P",mk_fun_ty ty bool_ty)]
197 (INST_TYPE [ty,aty] pth_exu)
198 and th1' = INST [bod,mk_var("P",mk_fun_ty ty bool_ty)]
199 (INST_TYPE [ty,aty] pth_not_exu)
201 MK_COMB(AP_TERM and_tm
202 (MK_EXISTS x (TRANS bth th_p)),
203 MK_FORALL x (MK_FORALL y
204 (MK_COMB(AP_TERM or_tm (TRANS (AP_TERM not_tm bth) th_n),
205 MK_COMB(AP_TERM or_tm
206 (TRANS (AP_TERM not_tm bth') th_n'),
209 MK_COMB(AP_TERM or_tm
210 (MK_FORALL x (TRANS (AP_TERM not_tm bth) th_n)),
211 MK_EXISTS x (MK_EXISTS y
212 (MK_COMB(AP_TERM and_tm (TRANS bth th_p),
213 MK_COMB(AP_TERM and_tm (TRANS bth' th_p'),
215 TRANS th1 th2,TRANS th1' th2'
216 | Comb(Const("~",_),t) ->
217 let th1,th2 = NNF_DCONV cf baseconvs t in
218 th2,TRANS (INST [t,p_tm] pth_not_not) th1
219 | _ -> try baseconvs tm
220 with Failure _ -> REFL tm,REFL(mk_neg tm) in
221 let rec NNF_CONV cf (base1,base2 as baseconvs) tm =
223 Comb(Comb(Const("/\\",_),l),r) ->
224 let th_lp = NNF_CONV cf baseconvs l
225 and th_rp = NNF_CONV cf baseconvs r in
226 MK_COMB(AP_TERM and_tm th_lp,th_rp)
227 | Comb(Comb(Const("\\/",_),l),r) ->
228 let th_lp = NNF_CONV cf baseconvs l
229 and th_rp = NNF_CONV cf baseconvs r in
230 MK_COMB(AP_TERM or_tm th_lp,th_rp)
231 | Comb(Comb(Const("==>",_),l),r) ->
232 let th_ln = NNF_CONV' cf baseconvs l
233 and th_rp = NNF_CONV cf baseconvs r in
234 TRANS (INST [l,p_tm; r,q_tm] pth_imp)
235 (MK_COMB(AP_TERM or_tm th_ln,th_rp))
236 | Comb(Comb(Const("=",Tyapp("fun",Tyapp("bool",_)::_)),l),r) ->
237 let th_lp,th_ln = NNF_DCONV cf base2 l
238 and th_rp,th_rn = NNF_DCONV cf base2 r in
240 TRANS (INST [l,p_tm; r,q_tm] pth_eq')
241 (MK_COMB(AP_TERM and_tm (MK_COMB(AP_TERM or_tm th_lp,th_rn)),
242 MK_COMB(AP_TERM or_tm th_ln,th_rp)))
244 TRANS (INST [l,p_tm; r,q_tm] pth_eq)
245 (MK_COMB(AP_TERM or_tm (MK_COMB(AP_TERM and_tm th_lp,th_rp)),
246 MK_COMB(AP_TERM and_tm th_ln,th_rn)))
247 | Comb(Const("!",Tyapp("fun",Tyapp("fun",ty::_)::_)) as q,
249 let th_p = NNF_CONV true baseconvs t in
250 AP_TERM q (ABS x th_p)
251 | Comb(Const("?",Tyapp("fun",Tyapp("fun",ty::_)::_)) as q,
253 let th_p = NNF_CONV cf baseconvs t in
254 AP_TERM q (ABS x th_p)
255 | Comb(Const("?!",Tyapp("fun",Tyapp("fun",ty::_)::_)),
256 (Abs(x,t) as bod)) ->
257 let y = variant (x::frees t) x
258 and th_p,th_n = NNF_DCONV cf base2 t in
259 let eq = mk_eq(y,x) in
260 let eth_p,eth_n = base2 eq
261 and bth = BETA (mk_comb(bod,x))
262 and bth' = BETA_CONV(mk_comb(bod,y)) in
263 let th_n' = INST [y,x] th_n in
264 let th1 = INST [bod,mk_var("P",mk_fun_ty ty bool_ty)]
265 (INST_TYPE [ty,aty] pth_exu)
267 MK_COMB(AP_TERM and_tm
268 (MK_EXISTS x (TRANS bth th_p)),
269 MK_FORALL x (MK_FORALL y
270 (MK_COMB(AP_TERM or_tm (TRANS (AP_TERM not_tm bth) th_n),
271 MK_COMB(AP_TERM or_tm
272 (TRANS (AP_TERM not_tm bth') th_n'),
275 | Comb(Const("~",_),t) -> NNF_CONV' cf baseconvs t
276 | _ -> try base1 tm with Failure _ -> REFL tm
277 and NNF_CONV' cf (base1,base2 as baseconvs) tm =
279 Comb(Comb(Const("/\\",_),l),r) ->
280 let th_ln = NNF_CONV' cf baseconvs l
281 and th_rn = NNF_CONV' cf baseconvs r in
282 TRANS (INST [l,p_tm; r,q_tm] pth_not_and)
283 (MK_COMB(AP_TERM or_tm th_ln,th_rn))
284 | Comb(Comb(Const("\\/",_),l),r) ->
285 let th_ln = NNF_CONV' cf baseconvs l
286 and th_rn = NNF_CONV' cf baseconvs r in
287 TRANS (INST [l,p_tm; r,q_tm] pth_not_or)
288 (MK_COMB(AP_TERM and_tm th_ln,th_rn))
289 | Comb(Comb(Const("==>",_),l),r) ->
290 let th_lp = NNF_CONV cf baseconvs l
291 and th_rn = NNF_CONV' cf baseconvs r in
292 TRANS (INST [l,p_tm; r,q_tm] pth_not_imp)
293 (MK_COMB(AP_TERM and_tm th_lp,th_rn))
294 | Comb(Comb(Const("=",Tyapp("fun",Tyapp("bool",_)::_)),l),r) ->
295 let th_lp,th_ln = NNF_DCONV cf base2 l
296 and th_rp,th_rn = NNF_DCONV cf base2 r in
298 TRANS (INST [l,p_tm; r,q_tm] pth_not_eq')
299 (MK_COMB(AP_TERM and_tm (MK_COMB(AP_TERM or_tm th_lp,th_rp)),
300 MK_COMB(AP_TERM or_tm th_ln,th_rn)))
302 TRANS (INST [l,p_tm; r,q_tm] pth_not_eq)
303 (MK_COMB(AP_TERM or_tm (MK_COMB(AP_TERM and_tm th_lp,th_rn)),
304 MK_COMB(AP_TERM and_tm th_ln,th_rp)))
305 | Comb(Const("!",Tyapp("fun",Tyapp("fun",ty::_)::_)),
306 (Abs(x,t) as bod)) ->
307 let th_n = NNF_CONV' cf baseconvs t in
308 let th1 = INST [bod,mk_var("P",mk_fun_ty ty bool_ty)]
309 (INST_TYPE [ty,aty] pth_not_forall)
310 and th2 = TRANS (AP_TERM not_tm (BETA(mk_comb(bod,x)))) th_n in
311 TRANS th1 (MK_EXISTS x th2)
312 | Comb(Const("?",Tyapp("fun",Tyapp("fun",ty::_)::_)),
313 (Abs(x,t) as bod)) ->
314 let th_n = NNF_CONV' true baseconvs t in
315 let th1 = INST [bod,mk_var("P",mk_fun_ty ty bool_ty)]
316 (INST_TYPE [ty,aty] pth_not_exists)
317 and th2 = TRANS (AP_TERM not_tm (BETA(mk_comb(bod,x)))) th_n in
318 TRANS th1 (MK_FORALL x th2)
319 | Comb(Const("?!",Tyapp("fun",Tyapp("fun",ty::_)::_)),
320 (Abs(x,t) as bod)) ->
321 let y = variant (x::frees t) x
322 and th_p,th_n = NNF_DCONV cf base2 t in
323 let eq = mk_eq(y,x) in
324 let eth_p,eth_n = base2 eq
325 and bth = BETA (mk_comb(bod,x))
326 and bth' = BETA_CONV(mk_comb(bod,y)) in
327 let th_p' = INST [y,x] th_p in
328 let th1' = INST [bod,mk_var("P",mk_fun_ty ty bool_ty)]
329 (INST_TYPE [ty,aty] pth_not_exu)
331 MK_COMB(AP_TERM or_tm
332 (MK_FORALL x (TRANS (AP_TERM not_tm bth) th_n)),
333 MK_EXISTS x (MK_EXISTS y
334 (MK_COMB(AP_TERM and_tm (TRANS bth th_p),
335 MK_COMB(AP_TERM and_tm (TRANS bth' th_p'),
338 | Comb(Const("~",_),t) ->
339 let th1 = NNF_CONV cf baseconvs t in
340 TRANS (INST [t,p_tm] pth_not_not) th1
341 | _ -> let tm' = mk_neg tm in try base1 tm' with Failure _ -> REFL tm' in
344 (* ------------------------------------------------------------------------- *)
345 (* Some common special cases. *)
346 (* ------------------------------------------------------------------------- *)
349 (GEN_NNF_CONV false (ALL_CONV,fun t -> REFL t,REFL(mk_neg t)) :conv);;
352 (GEN_NNF_CONV true (ALL_CONV,fun t -> REFL t,REFL(mk_neg t)) :conv);;
354 (* ------------------------------------------------------------------------- *)
355 (* Skolemize a term already in NNF (doesn't matter if it's not prenex). *)
356 (* ------------------------------------------------------------------------- *)
359 GEN_REWRITE_CONV TOP_DEPTH_CONV
360 [EXISTS_OR_THM; LEFT_EXISTS_AND_THM; RIGHT_EXISTS_AND_THM;
361 FORALL_AND_THM; LEFT_FORALL_OR_THM; RIGHT_FORALL_OR_THM;
362 FORALL_SIMP; EXISTS_SIMP] THENC
363 GEN_REWRITE_CONV REDEPTH_CONV
364 [RIGHT_AND_EXISTS_THM;
371 (* ------------------------------------------------------------------------- *)
372 (* Put a term already in NNF into prenex form. *)
373 (* ------------------------------------------------------------------------- *)
376 GEN_REWRITE_CONV REDEPTH_CONV
377 [AND_FORALL_THM; LEFT_AND_FORALL_THM; RIGHT_AND_FORALL_THM;
378 LEFT_OR_FORALL_THM; RIGHT_OR_FORALL_THM;
379 OR_EXISTS_THM; LEFT_OR_EXISTS_THM; RIGHT_OR_EXISTS_THM;
380 LEFT_AND_EXISTS_THM; RIGHT_AND_EXISTS_THM];;
382 (* ------------------------------------------------------------------------- *)
383 (* Weak and normal DNF conversion. The "weak" form gives a disjunction of *)
384 (* conjunctions, but has no particular associativity at either level and *)
385 (* may contain duplicates. The regular forms give canonical right-associate *)
386 (* lists without duplicates, but do not remove subsumed disjuncts. *)
388 (* In both cases the input term is supposed to be in NNF already. We do go *)
389 (* inside quantifiers and transform their body, but don't move them. *)
390 (* ------------------------------------------------------------------------- *)
392 let WEAK_DNF_CONV,DNF_CONV =
393 let pth1 = TAUT `a /\ (b \/ c) <=> a /\ b \/ a /\ c`
394 and pth2 = TAUT `(a \/ b) /\ c <=> a /\ c \/ b /\ c`
395 and a_tm = `a:bool` and b_tm = `b:bool` and c_tm = `c:bool` in
396 let rec distribute tm =
398 Comb(Comb(Const("/\\",_),a),Comb(Comb(Const("\\/",_),b),c)) ->
399 let th = INST [a,a_tm; b,b_tm; c,c_tm] pth1 in
400 TRANS th (BINOP_CONV distribute (rand(concl th)))
401 | Comb(Comb(Const("/\\",_),Comb(Comb(Const("\\/",_),a),b)),c) ->
402 let th = INST [a,a_tm; b,b_tm; c,c_tm] pth2 in
403 TRANS th (BINOP_CONV distribute (rand(concl th)))
406 DEPTH_BINOP_CONV `(\/)` CONJ_CANON_CONV THENC DISJ_CANON_CONV in
409 Comb(Const("!",_),Abs(_,_))
410 | Comb(Const("?",_),Abs(_,_)) -> BINDER_CONV weakdnf tm
411 | Comb(Comb(Const("\\/",_),_),_) -> BINOP_CONV weakdnf tm
412 | Comb(Comb(Const("/\\",_) as op,l),r) ->
413 let th = MK_COMB(AP_TERM op (weakdnf l),weakdnf r) in
414 TRANS th (distribute(rand(concl th)))
416 and substrongdnf tm =
418 Comb(Const("!",_),Abs(_,_))
419 | Comb(Const("?",_),Abs(_,_)) -> BINDER_CONV strongdnf tm
420 | Comb(Comb(Const("\\/",_),_),_) -> BINOP_CONV substrongdnf tm
421 | Comb(Comb(Const("/\\",_) as op,l),r) ->
422 let th = MK_COMB(AP_TERM op (substrongdnf l),substrongdnf r) in
423 TRANS th (distribute(rand(concl th)))
426 let th = substrongdnf tm in
427 TRANS th (strengthen(rand(concl th))) in
430 (* ------------------------------------------------------------------------- *)
431 (* Likewise for CNF. *)
432 (* ------------------------------------------------------------------------- *)
434 let WEAK_CNF_CONV,CNF_CONV =
435 let pth1 = TAUT `a \/ (b /\ c) <=> (a \/ b) /\ (a \/ c)`
436 and pth2 = TAUT `(a /\ b) \/ c <=> (a \/ c) /\ (b \/ c)`
437 and a_tm = `a:bool` and b_tm = `b:bool` and c_tm = `c:bool` in
438 let rec distribute tm =
440 Comb(Comb(Const("\\/",_),a),Comb(Comb(Const("/\\",_),b),c)) ->
441 let th = INST [a,a_tm; b,b_tm; c,c_tm] pth1 in
442 TRANS th (BINOP_CONV distribute (rand(concl th)))
443 | Comb(Comb(Const("\\/",_),Comb(Comb(Const("/\\",_),a),b)),c) ->
444 let th = INST [a,a_tm; b,b_tm; c,c_tm] pth2 in
445 TRANS th (BINOP_CONV distribute (rand(concl th)))
448 DEPTH_BINOP_CONV `(/\)` DISJ_CANON_CONV THENC CONJ_CANON_CONV in
451 Comb(Const("!",_),Abs(_,_))
452 | Comb(Const("?",_),Abs(_,_)) -> BINDER_CONV weakcnf tm
453 | Comb(Comb(Const("/\\",_),_),_) -> BINOP_CONV weakcnf tm
454 | Comb(Comb(Const("\\/",_) as op,l),r) ->
455 let th = MK_COMB(AP_TERM op (weakcnf l),weakcnf r) in
456 TRANS th (distribute(rand(concl th)))
458 and substrongcnf tm =
460 Comb(Const("!",_),Abs(_,_))
461 | Comb(Const("?",_),Abs(_,_)) -> BINDER_CONV strongcnf tm
462 | Comb(Comb(Const("/\\",_),_),_) -> BINOP_CONV substrongcnf tm
463 | Comb(Comb(Const("\\/",_) as op,l),r) ->
464 let th = MK_COMB(AP_TERM op (substrongcnf l),substrongcnf r) in
465 TRANS th (distribute(rand(concl th)))
468 let th = substrongcnf tm in
469 TRANS th (strengthen(rand(concl th))) in
472 (* ------------------------------------------------------------------------- *)
473 (* Simply right-associate w.r.t. a binary operator. *)
474 (* ------------------------------------------------------------------------- *)
477 let th' = SYM(SPEC_ALL th) in
478 let opx,yopz = dest_comb(rhs(concl th')) in
479 let op,x = dest_comb opx in
480 let y = lhand yopz and z = rand yopz in
483 Comb(Comb(op',Comb(Comb(op'',p),q)),r) when op' = op & op'' = op ->
484 let th1 = INST [p,x; q,y; r,z] th' in
485 let l,r' = dest_comb(rand(concl th1)) in
486 let th2 = AP_TERM l (distrib r') in
487 let th3 = distrib(rand(concl th2)) in
488 TRANS th1 (TRANS th2 th3)
492 Comb(Comb(op',p) as l,q) when op' = op ->
493 let th = AP_TERM l (assoc q) in
494 TRANS th (distrib(rand(concl th)))
498 (* ------------------------------------------------------------------------- *)
499 (* Eliminate select terms from a goal. *)
500 (* ------------------------------------------------------------------------- *)
502 let SELECT_ELIM_TAC =
503 let SELECT_ELIM_CONV =
504 let SELECT_ELIM_THM =
506 (`(P:A->bool)((@) P) <=> (?) P`,
507 REWRITE_TAC[EXISTS_THM] THEN BETA_TAC THEN REFL_TAC)
508 and ptm = `P:A->bool` in
509 fun tm -> let stm,atm = dest_comb tm in
510 if is_const stm & fst(dest_const stm) = "@" then
511 CONV_RULE(LAND_CONV BETA_CONV)
512 (PINST [type_of(bndvar atm),aty] [atm,ptm] pth)
513 else failwith "SELECT_ELIM_THM: not a select-term" in
515 PURE_REWRITE_CONV (map SELECT_ELIM_THM (find_terms is_select tm)) tm in
516 let SELECT_ELIM_ICONV =
518 let pth = ISPEC `P:A->bool` SELECT_AX
519 and ptm = `P:A->bool` in
520 fun tm -> let stm,atm = dest_comb tm in
521 if is_const stm & fst(dest_const stm) = "@" then
522 let fvs = frees atm in
523 let th1 = PINST [type_of(bndvar atm),aty] [atm,ptm] pth in
524 let th2 = CONV_RULE(BINDER_CONV (BINOP_CONV BETA_CONV)) th1 in
526 else failwith "SELECT_AX_THM: not a select-term" in
527 let SELECT_ELIM_ICONV tm =
528 let t = find_term is_select tm in
529 let th1 = SELECT_AX_THM t in
530 let itm = mk_imp(concl th1,tm) in
531 let th2 = DISCH_ALL (MP (ASSUME itm) th1) in
533 let fty = itlist (mk_fun_ty o type_of) fvs (type_of t) in
535 and atm = list_mk_abs(fvs,t) in
536 let rawdef = mk_eq(fn,atm) in
537 let def = GENL fvs (SYM(RIGHT_BETAS fvs (ASSUME rawdef))) in
538 let th3 = PURE_REWRITE_CONV[def] (lhand(concl th2)) in
539 let gtm = mk_forall(fn,rand(concl th3)) in
540 let th4 = EQ_MP (SYM th3) (SPEC fn (ASSUME gtm)) in
541 let th5 = IMP_TRANS (DISCH gtm th4) th2 in
542 MP (INST [atm,fn] (DISCH rawdef th5)) (REFL atm) in
543 let rec SELECT_ELIMS_ICONV tm =
544 try let th = SELECT_ELIM_ICONV tm in
545 let tm' = lhand(concl th) in
546 IMP_TRANS (SELECT_ELIMS_ICONV tm') th
547 with Failure _ -> DISCH tm (ASSUME tm) in
548 SELECT_ELIMS_ICONV in
549 CONV_TAC SELECT_ELIM_CONV THEN W(MATCH_MP_TAC o SELECT_ELIM_ICONV o snd);;
551 (* ------------------------------------------------------------------------- *)
552 (* Eliminate all lambda-terms except those part of quantifiers. *)
553 (* ------------------------------------------------------------------------- *)
555 let LAMBDA_ELIM_CONV =
556 let HALF_MK_ABS_CONV =
558 (`(s = \x. t x) <=> (!x. s x = t x)`,
559 REWRITE_TAC[FUN_EQ_THM]) in
561 if vs = [] then REFL tm else
562 (GEN_REWRITE_CONV I [pth] THENC BINDER_CONV(conv (tl vs))) tm in
564 let rec find_lambda tm =
566 else if is_var tm or is_const tm then failwith "find_lambda"
567 else if is_abs tm then tm else
568 if is_forall tm or is_exists tm or is_uexists tm
569 then find_lambda (body(rand tm)) else
570 let l,r = dest_comb tm in
571 try find_lambda l with Failure _ -> find_lambda r in
572 let rec ELIM_LAMBDA conv tm =
573 try conv tm with Failure _ ->
574 if is_abs tm then ABS_CONV (ELIM_LAMBDA conv) tm
575 else if is_var tm or is_const tm then REFL tm else
576 if is_forall tm or is_exists tm or is_uexists tm
577 then BINDER_CONV (ELIM_LAMBDA conv) tm
578 else COMB_CONV (ELIM_LAMBDA conv) tm in
581 (`(!a. (a = c) ==> (P = Q a)) ==> (P <=> !a. (a = c) ==> Q a)`,
582 SIMP_TAC[LEFT_FORALL_IMP_THM; EXISTS_REFL]) in
585 let atm = find_lambda tm in
586 let v,bod = dest_abs atm in
587 let vs = frees atm in
588 let vs' = vs @ [v] in
589 let aatm = list_mk_abs(vs,atm) in
590 let f = genvar(type_of aatm) in
591 let eq = mk_eq(f,aatm) in
592 let th1 = SYM(RIGHT_BETAS vs (ASSUME eq)) in
593 let th2 = ELIM_LAMBDA(GEN_REWRITE_CONV I [th1]) tm in
594 let th3 = APPLY_PTH (GEN f (DISCH_ALL th2)) in
595 CONV_RULE(RAND_CONV(BINDER_CONV(LAND_CONV (HALF_MK_ABS_CONV vs')))) th3 in
597 try (LAMB1_CONV THENC conv) tm with Failure _ -> REFL tm in
600 (* ------------------------------------------------------------------------- *)
601 (* Eliminate conditionals; CONDS_ELIM_CONV aims for disjunctive splitting, *)
602 (* for refutation procedures, and CONDS_CELIM_CONV for conjunctive. *)
603 (* Both switch modes "sensibly" when going through a quantifier. *)
604 (* ------------------------------------------------------------------------- *)
606 let CONDS_ELIM_CONV,CONDS_CELIM_CONV =
608 (`((b <=> F) ==> x = x0) /\ ((b <=> T) ==> x = x1)
609 ==> x = (b /\ x1 \/ ~b /\ x0)`,
610 BOOL_CASES_TAC `b:bool` THEN ASM_REWRITE_TAC[])
612 (`((b <=> F) ==> x = x0) /\ ((b <=> T) ==> x = x1)
613 ==> x = ((~b \/ x1) /\ (b \/ x0))`,
614 BOOL_CASES_TAC `b:bool` THEN ASM_REWRITE_TAC[])
615 and propsimps = basic_net()
616 and false_tm = `F` and true_tm = `T` in
617 let match_th = MATCH_MP th_cond and match_th' = MATCH_MP th_cond'
618 and propsimp_conv = DEPTH_CONV(REWRITES_CONV propsimps)
620 let cnv = TRY_CONV(REWRITES_CONV propsimps) in
621 BINOP_CONV cnv THENC cnv in
622 let rec find_conditional fvs tm =
625 if is_cond tm & intersect (frees(lhand s)) fvs = [] then tm
626 else (try (find_conditional fvs s)
627 with Failure _ -> find_conditional fvs t)
628 | Abs(x,t) -> find_conditional (x::fvs) t
629 | _ -> failwith "find_conditional" in
630 let rec CONDS_ELIM_CONV dfl tm =
631 try let t = find_conditional [] tm in
632 let p = lhand(rator t) in
634 if p = false_tm or p = true_tm then propsimp_conv tm else
635 let asm_0 = mk_eq(p,false_tm) and asm_1 = mk_eq(p,true_tm) in
636 let simp_0 = net_of_thm false (ASSUME asm_0) propsimps
637 and simp_1 = net_of_thm false (ASSUME asm_1) propsimps in
638 let th_0 = DISCH asm_0 (DEPTH_CONV(REWRITES_CONV simp_0) tm)
639 and th_1 = DISCH asm_1 (DEPTH_CONV(REWRITES_CONV simp_1) tm) in
640 let th_2 = CONJ th_0 th_1 in
641 let th_3 = if dfl then match_th th_2 else match_th' th_2 in
642 TRANS th_3 (proptsimp_conv(rand(concl th_3))) in
643 CONV_RULE (RAND_CONV (CONDS_ELIM_CONV dfl)) th_new
646 RAND_CONV (CONDS_ELIM_CONV (not dfl)) tm
647 else if is_conj tm or is_disj tm then
648 BINOP_CONV (CONDS_ELIM_CONV dfl) tm
649 else if is_imp tm or is_iff tm then
650 COMB2_CONV (RAND_CONV (CONDS_ELIM_CONV (not dfl)))
651 (CONDS_ELIM_CONV dfl) tm
652 else if is_forall tm then
653 BINDER_CONV (CONDS_ELIM_CONV false) tm
654 else if is_exists tm or is_uexists tm then
655 BINDER_CONV (CONDS_ELIM_CONV true) tm
657 CONDS_ELIM_CONV true,CONDS_ELIM_CONV false;;
659 (* ------------------------------------------------------------------------- *)
660 (* Fix up all head arities to be consistent, in "first order logic" style. *)
661 (* Applied to the assumptions (not conclusion) in a goal. *)
662 (* ------------------------------------------------------------------------- *)
665 let rec get_heads lconsts tm (cheads,vheads as sofar) =
666 try let v,bod = dest_forall tm in
667 get_heads (subtract lconsts [v]) bod sofar
668 with Failure _ -> try
669 let l,r = try dest_conj tm with Failure _ -> dest_disj tm in
670 get_heads lconsts l (get_heads lconsts r sofar)
671 with Failure _ -> try
672 let tm' = dest_neg tm in
673 get_heads lconsts tm' sofar
675 let hop,args = strip_comb tm in
676 let len = length args in
678 if is_const hop or mem hop lconsts
679 then (insert (hop,len) cheads,vheads)
680 else if len > 0 then (cheads,insert (hop,len) vheads) else sofar in
681 itlist (get_heads lconsts) args newheads in
682 let get_thm_heads th sofar =
683 get_heads (freesl(hyp th)) (concl th) sofar in
686 (`!(f:A->B) x. f x = I f x`,
687 REWRITE_TAC[I_THM]) in
689 let rec APP_N_CONV n tm =
690 if n = 1 then APP_CONV tm
691 else (RATOR_CONV (APP_N_CONV (n - 1)) THENC APP_CONV) tm in
692 let rec FOL_CONV hddata tm =
693 if is_forall tm then BINDER_CONV (FOL_CONV hddata) tm
694 else if is_conj tm or is_disj tm then BINOP_CONV (FOL_CONV hddata) tm else
695 let op,args = strip_comb tm in
696 let th = rev_itlist (C (curry MK_COMB))
697 (map (FOL_CONV hddata) args) (REFL op) in
698 let tm' = rand(concl th) in
699 let n = try length args - assoc op hddata with Failure _ -> 0 in
701 else TRANS th (APP_N_CONV n tm') in
702 let GEN_FOL_CONV (cheads,vheads) =
705 let hops = setify (map fst cheads) in
708 (fun (k,n) -> if k = h then n else fail()) cheads in
709 if length ns < 2 then fail() else h,end_itlist min ns in
710 mapfilter getmin hops
712 map (fun t -> if is_const t & fst(dest_const t) = "="
714 (setify (map fst (vheads @ cheads))) in
717 let headsp = itlist (get_thm_heads o snd) asl ([],[]) in
718 RULE_ASSUM_TAC(CONV_RULE(GEN_FOL_CONV headsp)) gl;;
720 (* ------------------------------------------------------------------------- *)
721 (* Depth conversion to apply at "atomic" formulas in "first-order" term. *)
722 (* ------------------------------------------------------------------------- *)
724 let rec PROP_ATOM_CONV conv tm =
726 Comb((Const("!",_) | Const("?",_) | Const("?!",_)),Abs(_,_))
727 -> BINDER_CONV (PROP_ATOM_CONV conv) tm
729 ((Const("/\\",_) | Const("\\/",_) | Const("==>",_) |
730 (Const("=",Tyapp("fun",[Tyapp("bool",[]);_])))),_),_)
731 -> BINOP_CONV (PROP_ATOM_CONV conv) tm
732 | Comb(Const("~",_),_) -> RAND_CONV (PROP_ATOM_CONV conv) tm
733 | _ -> TRY_CONV conv tm;;