1 type ite = False | True | Atomic of int | Ite of ite*ite*ite;;
5 Ite(False,y,z) -> norm z
6 | Ite(True,y,z) -> norm y
7 | Ite(Atomic i,y,z) -> Ite(Atomic i,norm y,norm z)
8 | Ite(Ite(u,v,w),y,z) -> norm(Ite(u,Ite(v,y,z),Ite(w,y,z)))
11 let ite_INDUCT,ite_RECURSION = define_type
12 "ite = False | True | Atomic num | Ite ite ite ite";;
14 let eth = prove_general_recursive_function_exists
15 `?norm. (norm False = False) /\
17 (!i. norm (Atomic i) = Atomic i) /\
18 (!y z. norm (Ite False y z) = norm z) /\
19 (!y z. norm (Ite True y z) = norm y) /\
20 (!i y z. norm (Ite (Atomic i) y z) =
21 Ite (Atomic i) (norm y) (norm z)) /\
22 (!u v w y z. norm (Ite (Ite u v w) y z) =
23 norm (Ite u (Ite v y z) (Ite w y z)))`;;
26 `(sizeof False = 1) /\
28 (sizeof(Atomic i) = 1) /\
29 (sizeof(Ite x y z) = sizeof x * (1 + sizeof y + sizeof z))`;;
34 EXISTS_TAC `MEASURE sizeof` THEN
35 REWRITE_TAC[WF_MEASURE; MEASURE_LE; MEASURE; sizeof] THEN ARITH_TAC) in
38 let norm = new_specification ["norm"] eth';;
40 let SIZEOF_INDUCT = REWRITE_RULE[WF_IND; MEASURE] (ISPEC`sizeof` WF_MEASURE);;
43 (`!e. ~(sizeof e = 0)`,
44 MATCH_MP_TAC ite_INDUCT THEN SIMP_TAC[sizeof; ADD_EQ_0; MULT_EQ_0; ARITH]);;
46 let ITE_INDUCT = prove
50 (!y z. P z ==> P(Ite False y z)) /\
51 (!y z. P y ==> P(Ite True y z)) /\
52 (!i y z. P y /\ P z ==> P (Ite (Atomic i) y z)) /\
53 (!u v w x y z. P(Ite u (Ite v y z) (Ite w y z))
54 ==> P(Ite (Ite u v w) y z))
56 GEN_TAC THEN STRIP_TAC THEN MATCH_MP_TAC SIZEOF_INDUCT THEN
57 MATCH_MP_TAC ite_INDUCT THEN ASM_REWRITE_TAC[] THEN
58 MATCH_MP_TAC ite_INDUCT THEN POP_ASSUM_LIST
59 (fun ths -> REPEAT STRIP_TAC THEN FIRST(mapfilter MATCH_MP_TAC ths)) THEN
60 REPEAT CONJ_TAC THEN FIRST_X_ASSUM MATCH_MP_TAC THEN
61 POP_ASSUM_LIST(K ALL_TAC) THEN
62 REWRITE_TAC[sizeof] THEN TRY ARITH_TAC THEN
63 REWRITE_TAC[LEFT_ADD_DISTRIB; RIGHT_ADD_DISTRIB; MULT_CLAUSES] THEN
64 REWRITE_TAC[MULT_AC; ADD_AC; LT_ADD_LCANCEL] THEN
65 REWRITE_TAC[ADD_ASSOC; LT_ADD_RCANCEL] THEN
66 MATCH_MP_TAC(ARITH_RULE `~(b = 0) /\ ~(c = 0) ==> a < (b + a) + c`) THEN
67 REWRITE_TAC[MULT_EQ_0; SIZEOF_NZ]);;
69 let normalized = define
70 `(normalized False <=> T) /\
71 (normalized True <=> T) /\
72 (normalized(Atomic a) <=> T) /\
73 (normalized(Ite False x y) <=> F) /\
74 (normalized(Ite True x y) <=> F) /\
75 (normalized(Ite (Atomic a) x y) <=> normalized x /\ normalized y) /\
76 (normalized(Ite (Ite u v w) x y) <=> F)`;;
78 let NORMALIZED_NORM = prove
79 (`!e. normalized(norm e)`,
80 MATCH_MP_TAC ITE_INDUCT THEN REWRITE_TAC[norm; normalized]);;
82 let NORMALIZED_INDUCT = prove
86 (!i x y. P x /\ P y ==> P (Ite (Atomic i) x y))
87 ==> !e. normalized e ==> P e`,
88 STRIP_TAC THEN MATCH_MP_TAC ite_INDUCT THEN ASM_REWRITE_TAC[normalized] THEN
89 MATCH_MP_TAC ite_INDUCT THEN ASM_MESON_TAC[normalized]);;
92 `(holds v False <=> F) /\
93 (holds v True <=> T) /\
94 (holds v (Atomic i) <=> v(i)) /\
95 (holds v (Ite b x y) <=> if holds v b then holds v x else holds v y)`;;
97 let HOLDS_NORM = prove
98 (`!e v. holds v (norm e) <=> holds v e`,
99 MATCH_MP_TAC ITE_INDUCT THEN SIMP_TAC[holds; norm] THEN
100 REPEAT STRIP_TAC THEN CONV_TAC TAUT);;
103 `(taut (t,f) False <=> F) /\
104 (taut (t,f) True <=> T) /\
105 (taut (t,f) (Atomic i) <=> MEM i t) /\
106 (taut (t,f) (Ite (Atomic i) x y) <=>
107 if MEM i t then taut (t,f) x
108 else if MEM i f then taut (t,f) y
109 else taut (CONS i t,f) x /\ taut (t,CONS i f) y)`;;
111 let tautology = define `tautology e = taut([],[]) (norm e)`;;
113 let NORMALIZED_TAUT = prove
115 ==> !f t. (!a. ~(MEM a t /\ MEM a f))
116 ==> (taut (t,f) e <=>
117 !v. (!a. MEM a t ==> v(a)) /\ (!a. MEM a f ==> ~v(a))
119 MATCH_MP_TAC NORMALIZED_INDUCT THEN REWRITE_TAC[holds; taut] THEN
120 REWRITE_TAC[NOT_FORALL_THM] THEN REPEAT CONJ_TAC THENL
121 [REPEAT STRIP_TAC THEN EXISTS_TAC `\a:num. MEM a t` THEN ASM_MESON_TAC[];
122 REPEAT STRIP_TAC THEN EQ_TAC THENL
123 [ALL_TAC; DISCH_THEN MATCH_MP_TAC] THEN ASM_MESON_TAC[];
124 REPEAT STRIP_TAC THEN REPEAT(COND_CASES_TAC THEN ASM_SIMP_TAC[])] THEN
125 ASM_SIMP_TAC[MEM; RIGHT_OR_DISTRIB; LEFT_OR_DISTRIB;
126 MESON[] `(!a. ~(MEM a t /\ a = i)) <=> ~(MEM i t)`;
127 MESON[] `(!a. ~(a = i /\ MEM a f)) <=> ~(MEM i f)`] THEN
128 ASM_REWRITE_TAC[AND_FORALL_THM] THEN AP_TERM_TAC THEN ABS_TAC THEN
131 let TAUTOLOGY = prove
132 (`!e. tautology e <=> !v. holds v e`,
133 MESON_TAC[tautology; HOLDS_NORM; NORMALIZED_TAUT; MEM; NORMALIZED_NORM]);;
135 let HOLDS_BACK = prove
136 (`!v. (F <=> holds v False) /\
137 (T <=> holds v True) /\
138 (!i. v i <=> holds v (Atomic i)) /\
139 (!p. ~holds v p <=> holds v (Ite p False True)) /\
140 (!p q. (holds v p /\ holds v q) <=> holds v (Ite p q False)) /\
141 (!p q. (holds v p \/ holds v q) <=> holds v (Ite p True q)) /\
142 (!p q. (holds v p <=> holds v q) <=>
143 holds v (Ite p q (Ite q False True))) /\
144 (!p q. holds v p ==> holds v q <=> holds v (Ite p q True))`,
145 REWRITE_TAC[holds] THEN CONV_TAC TAUT);;
147 let COND_CONV = GEN_REWRITE_CONV I [COND_CLAUSES];;
148 let AND_CONV = GEN_REWRITE_CONV I [TAUT `(F /\ a <=> F) /\ (T /\ a <=> a)`];;
149 let OR_CONV = GEN_REWRITE_CONV I [TAUT `(F \/ a <=> a) /\ (T \/ a <=> T)`];;
151 let rec COMPUTE_DEPTH_CONV conv tm =
153 (RATOR_CONV(LAND_CONV(COMPUTE_DEPTH_CONV conv)) THENC
155 COMPUTE_DEPTH_CONV conv) tm
156 else if is_conj tm then
157 (LAND_CONV (COMPUTE_DEPTH_CONV conv) THENC
159 COMPUTE_DEPTH_CONV conv) tm
160 else if is_disj tm then
161 (LAND_CONV (COMPUTE_DEPTH_CONV conv) THENC
163 COMPUTE_DEPTH_CONV conv) tm
165 (SUB_CONV (COMPUTE_DEPTH_CONV conv) THENC
166 TRY_CONV(conv THENC COMPUTE_DEPTH_CONV conv)) tm;;
168 g `!v. v 1 \/ v 2 \/ v 3 \/ v 4 \/ v 5 \/ v 6 \/
169 ~v 1 \/ ~v 2 \/ ~v 3 \/ ~v 4 \/ ~v 5 \/ ~v 6`;;
171 e(MP_TAC HOLDS_BACK THEN MATCH_MP_TAC MONO_FORALL THEN
172 GEN_TAC THEN DISCH_THEN(fun th -> REWRITE_TAC[th]) THEN
173 SPEC_TAC(`v:num->bool`,`v:num->bool`) THEN
174 REWRITE_TAC[GSYM TAUTOLOGY; tautology]);;
176 time e (GEN_REWRITE_TAC COMPUTE_DEPTH_CONV [norm; taut; MEM; ARITH_EQ]);;
178 ignore(b()); time e (REWRITE_TAC[norm; taut; MEM; ARITH_EQ]);;