1 (* ========================================================================= *)
2 (* Properties of complex polynomials (not canonically represented). *)
3 (* ========================================================================= *)
5 needs "Complex/complexnumbers.ml";;
9 parse_as_infix("++",(16,"right"));;
10 parse_as_infix("**",(20,"right"));;
11 parse_as_infix("##",(20,"right"));;
12 parse_as_infix("divides",(14,"right"));;
13 parse_as_infix("exp",(22,"right"));;
15 do_list override_interface
16 ["++",`poly_add:complex list->complex list->complex list`;
17 "**",`poly_mul:complex list->complex list->complex list`;
18 "##",`poly_cmul:complex->complex list->complex list`;
19 "neg",`poly_neg:complex list->complex list`;
20 "divides",`poly_divides:complex list->complex list->bool`;
21 "exp",`poly_exp:complex list -> num -> complex list`;
22 "diff",`poly_diff:complex list->complex list`];;
24 let SIMPLE_COMPLEX_ARITH tm = prove(tm,SIMPLE_COMPLEX_ARITH_TAC);;
26 (* ------------------------------------------------------------------------- *)
28 (* ------------------------------------------------------------------------- *)
30 let poly = new_recursive_definition list_RECURSION
31 `(poly [] x = Cx(&0)) /\
32 (poly (CONS h t) x = h + x * poly t x)`;;
34 (* ------------------------------------------------------------------------- *)
35 (* Arithmetic operations on polynomials. *)
36 (* ------------------------------------------------------------------------- *)
38 let poly_add = new_recursive_definition list_RECURSION
41 (if l2 = [] then CONS h t
42 else CONS (h + HD l2) (t ++ TL l2)))`;;
44 let poly_cmul = new_recursive_definition list_RECURSION
46 (c ## (CONS h t) = CONS (c * h) (c ## t))`;;
48 let poly_neg = new_definition
49 `neg = (##) (--(Cx(&1)))`;;
51 let poly_mul = new_recursive_definition list_RECURSION
54 if t = [] then h ## l2
55 else (h ## l2) ++ CONS (Cx(&0)) (t ** l2))`;;
57 let poly_exp = new_recursive_definition num_RECURSION
58 `(p exp 0 = [Cx(&1)]) /\
59 (p exp (SUC n) = p ** p exp n)`;;
61 (* ------------------------------------------------------------------------- *)
62 (* Useful clausifications. *)
63 (* ------------------------------------------------------------------------- *)
65 let POLY_ADD_CLAUSES = prove
68 ((CONS h1 t1) ++ (CONS h2 t2) = CONS (h1 + h2) (t1 ++ t2))`,
69 REWRITE_TAC[poly_add; NOT_CONS_NIL; HD; TL] THEN
70 SPEC_TAC(`p1:complex list`,`p1:complex list`) THEN
71 LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[poly_add]);;
73 let POLY_CMUL_CLAUSES = prove
75 (c ## (CONS h t) = CONS (c * h) (c ## t))`,
76 REWRITE_TAC[poly_cmul]);;
78 let POLY_NEG_CLAUSES = prove
80 (neg (CONS h t) = CONS (--h) (neg t))`,
81 REWRITE_TAC[poly_neg; POLY_CMUL_CLAUSES;
82 COMPLEX_MUL_LNEG; COMPLEX_MUL_LID]);;
84 let POLY_MUL_CLAUSES = prove
86 ([h1] ** p2 = h1 ## p2) /\
87 ((CONS h1 (CONS k1 t1)) ** p2 =
88 h1 ## p2 ++ CONS (Cx(&0)) (CONS k1 t1 ** p2))`,
89 REWRITE_TAC[poly_mul; NOT_CONS_NIL]);;
91 (* ------------------------------------------------------------------------- *)
92 (* Various natural consequences of syntactic definitions. *)
93 (* ------------------------------------------------------------------------- *)
96 (`!p1 p2 x. poly (p1 ++ p2) x = poly p1 x + poly p2 x`,
97 LIST_INDUCT_TAC THEN REWRITE_TAC[poly_add; poly; COMPLEX_ADD_LID] THEN
99 ASM_REWRITE_TAC[NOT_CONS_NIL; HD; TL; poly; COMPLEX_ADD_RID] THEN
100 SIMPLE_COMPLEX_ARITH_TAC);;
102 let POLY_CMUL = prove
103 (`!p c x. poly (c ## p) x = c * poly p x`,
104 LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[poly; poly_cmul] THEN
105 SIMPLE_COMPLEX_ARITH_TAC);;
108 (`!p x. poly (neg p) x = --(poly p x)`,
109 REWRITE_TAC[poly_neg; POLY_CMUL] THEN
110 SIMPLE_COMPLEX_ARITH_TAC);;
113 (`!x p1 p2. poly (p1 ** p2) x = poly p1 x * poly p2 x`,
114 GEN_TAC THEN LIST_INDUCT_TAC THEN
115 REWRITE_TAC[poly_mul; poly; COMPLEX_MUL_LZERO; POLY_CMUL; POLY_ADD] THEN
116 SPEC_TAC(`h:complex`,`h:complex`) THEN
117 SPEC_TAC(`t:complex list`,`t:complex list`) THEN
119 REWRITE_TAC[poly_mul; POLY_CMUL; POLY_ADD; poly; POLY_CMUL;
120 COMPLEX_MUL_RZERO; COMPLEX_ADD_RID; NOT_CONS_NIL] THEN
121 ASM_REWRITE_TAC[POLY_ADD; POLY_CMUL; poly] THEN
122 SIMPLE_COMPLEX_ARITH_TAC);;
125 (`!p n x. poly (p exp n) x = (poly p x) pow n`,
126 GEN_TAC THEN INDUCT_TAC THEN
127 ASM_REWRITE_TAC[poly_exp; complex_pow; POLY_MUL] THEN
128 REWRITE_TAC[poly] THEN SIMPLE_COMPLEX_ARITH_TAC);;
130 (* ------------------------------------------------------------------------- *)
132 (* ------------------------------------------------------------------------- *)
134 let POLY_ADD_RZERO = prove
135 (`!p. poly (p ++ []) = poly p`,
136 REWRITE_TAC[FUN_EQ_THM; POLY_ADD; poly; COMPLEX_ADD_RID]);;
138 let POLY_MUL_ASSOC = prove
139 (`!p q r. poly (p ** (q ** r)) = poly ((p ** q) ** r)`,
140 REWRITE_TAC[FUN_EQ_THM; POLY_MUL; COMPLEX_MUL_ASSOC]);;
142 let POLY_EXP_ADD = prove
143 (`!d n p. poly(p exp (n + d)) = poly(p exp n ** p exp d)`,
144 REWRITE_TAC[FUN_EQ_THM; POLY_MUL] THEN
145 INDUCT_TAC THEN ASM_REWRITE_TAC[POLY_MUL; ADD_CLAUSES; poly_exp; poly] THEN
146 SIMPLE_COMPLEX_ARITH_TAC);;
148 (* ------------------------------------------------------------------------- *)
149 (* Key property that f(a) = 0 ==> (x - a) divides p(x). Very delicate! *)
150 (* ------------------------------------------------------------------------- *)
152 let POLY_LINEAR_REM = prove
153 (`!t h. ?q r. CONS h t = [r] ++ [--a; Cx(&1)] ** q`,
154 LIST_INDUCT_TAC THEN REWRITE_TAC[] THENL
155 [GEN_TAC THEN EXISTS_TAC `[]:complex list` THEN
156 EXISTS_TAC `h:complex` THEN
157 REWRITE_TAC[poly_add; poly_mul; poly_cmul; NOT_CONS_NIL] THEN
158 REWRITE_TAC[HD; TL; COMPLEX_ADD_RID];
159 X_GEN_TAC `k:complex` THEN
160 POP_ASSUM(STRIP_ASSUME_TAC o SPEC `h:complex`) THEN
161 EXISTS_TAC `CONS (r:complex) q` THEN EXISTS_TAC `r * a + k` THEN
162 ASM_REWRITE_TAC[POLY_ADD_CLAUSES; POLY_MUL_CLAUSES; poly_cmul] THEN
163 REWRITE_TAC[CONS_11] THEN CONJ_TAC THENL
164 [SIMPLE_COMPLEX_ARITH_TAC; ALL_TAC] THEN
165 SPEC_TAC(`q:complex list`,`q:complex list`) THEN
167 REWRITE_TAC[POLY_ADD_CLAUSES; POLY_MUL_CLAUSES; poly_cmul] THEN
168 REWRITE_TAC[COMPLEX_ADD_RID; COMPLEX_MUL_LID] THEN
169 REWRITE_TAC[COMPLEX_ADD_AC]]);;
171 let POLY_LINEAR_DIVIDES = prove
172 (`!a p. (poly p a = Cx(&0)) <=> (p = []) \/ ?q. p = [--a; Cx(&1)] ** q`,
173 GEN_TAC THEN LIST_INDUCT_TAC THENL
174 [REWRITE_TAC[poly]; ALL_TAC] THEN
175 EQ_TAC THEN STRIP_TAC THENL
176 [DISJ2_TAC THEN STRIP_ASSUME_TAC(SPEC_ALL POLY_LINEAR_REM) THEN
177 EXISTS_TAC `q:complex list` THEN ASM_REWRITE_TAC[] THEN
178 SUBGOAL_THEN `r = Cx(&0)` SUBST_ALL_TAC THENL
179 [UNDISCH_TAC `poly (CONS h t) a = Cx(&0)` THEN
180 ASM_REWRITE_TAC[] THEN REWRITE_TAC[POLY_ADD; POLY_MUL] THEN
181 REWRITE_TAC[poly; COMPLEX_MUL_RZERO; COMPLEX_ADD_RID;
182 COMPLEX_MUL_RID] THEN
183 REWRITE_TAC[COMPLEX_ADD_LINV] THEN SIMPLE_COMPLEX_ARITH_TAC;
184 REWRITE_TAC[poly_mul] THEN REWRITE_TAC[NOT_CONS_NIL] THEN
185 SPEC_TAC(`q:complex list`,`q:complex list`) THEN LIST_INDUCT_TAC THENL
186 [REWRITE_TAC[poly_cmul; poly_add; NOT_CONS_NIL;
187 HD; TL; COMPLEX_ADD_LID];
188 REWRITE_TAC[poly_cmul; poly_add; NOT_CONS_NIL;
189 HD; TL; COMPLEX_ADD_LID]]];
190 ASM_REWRITE_TAC[] THEN REWRITE_TAC[poly];
191 ASM_REWRITE_TAC[] THEN REWRITE_TAC[poly] THEN
192 REWRITE_TAC[POLY_MUL] THEN REWRITE_TAC[poly] THEN
193 REWRITE_TAC[poly; COMPLEX_MUL_RZERO; COMPLEX_ADD_RID; COMPLEX_MUL_RID] THEN
194 REWRITE_TAC[COMPLEX_ADD_LINV] THEN SIMPLE_COMPLEX_ARITH_TAC]);;
196 (* ------------------------------------------------------------------------- *)
197 (* Thanks to the finesse of the above, we can use length rather than degree. *)
198 (* ------------------------------------------------------------------------- *)
200 let POLY_LENGTH_MUL = prove
201 (`!q. LENGTH([--a; Cx(&1)] ** q) = SUC(LENGTH q)`,
203 (`!p h k a. LENGTH (k ## p ++ CONS h (a ## p)) = SUC(LENGTH p)`,
205 ASM_REWRITE_TAC[poly_cmul; POLY_ADD_CLAUSES; LENGTH]) in
206 REWRITE_TAC[poly_mul; NOT_CONS_NIL; lemma]);;
208 (* ------------------------------------------------------------------------- *)
209 (* Thus a nontrivial polynomial of degree n has no more than n roots. *)
210 (* ------------------------------------------------------------------------- *)
212 let POLY_ROOTS_INDEX_LEMMA = prove
213 (`!n. !p. ~(poly p = poly []) /\ (LENGTH p = n)
214 ==> ?i. !x. (poly p x = Cx(&0)) ==> ?m. m <= n /\ (x = i m)`,
216 [REWRITE_TAC[LENGTH_EQ_NIL] THEN MESON_TAC[];
217 REPEAT STRIP_TAC THEN ASM_CASES_TAC `?a. poly p a = Cx(&0)` THENL
218 [UNDISCH_TAC `?a. poly p a = Cx(&0)` THEN
219 DISCH_THEN(CHOOSE_THEN MP_TAC) THEN
220 GEN_REWRITE_TAC LAND_CONV [POLY_LINEAR_DIVIDES] THEN
221 DISCH_THEN(DISJ_CASES_THEN MP_TAC) THENL [ASM_MESON_TAC[]; ALL_TAC] THEN
222 DISCH_THEN(X_CHOOSE_THEN `q:complex list` SUBST_ALL_TAC) THEN
223 FIRST_ASSUM(UNDISCH_TAC o check is_forall o concl) THEN
224 UNDISCH_TAC `~(poly ([-- a; Cx(&1)] ** q) = poly [])` THEN
225 POP_ASSUM MP_TAC THEN REWRITE_TAC[POLY_LENGTH_MUL; SUC_INJ] THEN
226 DISCH_TAC THEN ASM_CASES_TAC `poly q = poly []` THENL
227 [ASM_REWRITE_TAC[POLY_MUL; poly; COMPLEX_MUL_RZERO; FUN_EQ_THM];
228 DISCH_THEN(K ALL_TAC)] THEN
229 DISCH_THEN(MP_TAC o SPEC `q:complex list`) THEN ASM_REWRITE_TAC[] THEN
230 DISCH_THEN(X_CHOOSE_TAC `i:num->complex`) THEN
231 EXISTS_TAC `\m. if m = SUC n then a:complex else i m` THEN
232 REWRITE_TAC[POLY_MUL; LE; COMPLEX_ENTIRE] THEN
233 X_GEN_TAC `x:complex` THEN DISCH_THEN(DISJ_CASES_THEN MP_TAC) THENL
234 [DISCH_THEN(fun th -> EXISTS_TAC `SUC n` THEN MP_TAC th) THEN
235 REWRITE_TAC[poly] THEN SIMPLE_COMPLEX_ARITH_TAC;
236 DISCH_THEN(ANTE_RES_THEN MP_TAC) THEN
237 DISCH_THEN(X_CHOOSE_THEN `m:num` STRIP_ASSUME_TAC) THEN
238 EXISTS_TAC `m:num` THEN ASM_REWRITE_TAC[] THEN
239 COND_CASES_TAC THEN ASM_REWRITE_TAC[] THEN
240 UNDISCH_TAC `m:num <= n` THEN ASM_REWRITE_TAC[] THEN ARITH_TAC];
241 UNDISCH_TAC `~(?a. poly p a = Cx(&0))` THEN
242 REWRITE_TAC[NOT_EXISTS_THM] THEN DISCH_TAC THEN ASM_REWRITE_TAC[]]]);;
244 let POLY_ROOTS_INDEX_LENGTH = prove
245 (`!p. ~(poly p = poly [])
246 ==> ?i. !x. (poly p(x) = Cx(&0)) ==> ?n. n <= LENGTH p /\ (x = i n)`,
247 MESON_TAC[POLY_ROOTS_INDEX_LEMMA]);;
249 let POLY_ROOTS_FINITE_LEMMA = prove
250 (`!p. ~(poly p = poly [])
251 ==> ?N i. !x. (poly p(x) = Cx(&0)) ==> ?n:num. n < N /\ (x = i n)`,
252 MESON_TAC[POLY_ROOTS_INDEX_LENGTH; LT_SUC_LE]);;
254 let FINITE_LEMMA = prove
255 (`!i N P. (!x. P x ==> ?n:num. n < N /\ (x = i n))
256 ==> ?a. !x. P x ==> norm(x) < a`,
257 GEN_TAC THEN ONCE_REWRITE_TAC[RIGHT_IMP_EXISTS_THM] THEN INDUCT_TAC THENL
258 [REWRITE_TAC[LT] THEN MESON_TAC[]; ALL_TAC] THEN
259 X_GEN_TAC `P:complex->bool` THEN
260 POP_ASSUM(MP_TAC o SPEC `\z. P z /\ ~(z = (i:num->complex) N)`) THEN
261 DISCH_THEN(X_CHOOSE_TAC `a:real`) THEN
262 EXISTS_TAC `abs(a) + norm(i(N:num)) + &1` THEN
263 POP_ASSUM MP_TAC THEN REWRITE_TAC[LT] THEN
264 SUBGOAL_THEN `(!x. norm(x) < abs(a) + norm(x) + &1) /\
265 (!x y. norm(x) < a ==> norm(x) < abs(a) + norm(y) + &1)`
266 (fun th -> MP_TAC th THEN MESON_TAC[]) THEN
267 CONJ_TAC THENL [REAL_ARITH_TAC; ALL_TAC] THEN
268 REPEAT GEN_TAC THEN MP_TAC(SPEC `y:complex` COMPLEX_NORM_POS) THEN
271 let POLY_ROOTS_FINITE = prove
272 (`!p. ~(poly p = poly []) <=>
273 ?N i. !x. (poly p(x) = Cx(&0)) ==> ?n:num. n < N /\ (x = i n)`,
274 GEN_TAC THEN EQ_TAC THEN REWRITE_TAC[POLY_ROOTS_FINITE_LEMMA] THEN
275 REWRITE_TAC[FUN_EQ_THM; LEFT_IMP_EXISTS_THM; NOT_FORALL_THM; poly] THEN
276 MP_TAC(GENL [`i:num->complex`; `N:num`]
277 (SPECL [`i:num->complex`; `N:num`; `\x. poly p x = Cx(&0)`]
279 REWRITE_TAC[] THEN MESON_TAC[REAL_ARITH `~(abs(x) < x)`; COMPLEX_NORM_CX]);;
281 (* ------------------------------------------------------------------------- *)
282 (* Hence get entirety and cancellation for polynomials. *)
283 (* ------------------------------------------------------------------------- *)
285 let POLY_ENTIRE_LEMMA = prove
286 (`!p q. ~(poly p = poly []) /\ ~(poly q = poly [])
287 ==> ~(poly (p ** q) = poly [])`,
288 REPEAT GEN_TAC THEN REWRITE_TAC[POLY_ROOTS_FINITE] THEN
289 DISCH_THEN(CONJUNCTS_THEN MP_TAC) THEN
290 DISCH_THEN(X_CHOOSE_THEN `N2:num` (X_CHOOSE_TAC `i2:num->complex`)) THEN
291 DISCH_THEN(X_CHOOSE_THEN `N1:num` (X_CHOOSE_TAC `i1:num->complex`)) THEN
292 EXISTS_TAC `N1 + N2:num` THEN
293 EXISTS_TAC `\n:num. if n < N1 then i1(n):complex else i2(n - N1)` THEN
294 X_GEN_TAC `x:complex` THEN REWRITE_TAC[COMPLEX_ENTIRE; POLY_MUL] THEN
295 DISCH_THEN(DISJ_CASES_THEN (ANTE_RES_THEN (X_CHOOSE_TAC `n:num`))) THENL
296 [EXISTS_TAC `n:num` THEN ASM_REWRITE_TAC[] THEN
297 FIRST_ASSUM(MP_TAC o CONJUNCT1) THEN ARITH_TAC;
298 EXISTS_TAC `N1 + n:num` THEN ASM_REWRITE_TAC[LT_ADD_LCANCEL] THEN
299 REWRITE_TAC[ARITH_RULE `~(m + n < m:num)`] THEN
300 AP_TERM_TAC THEN ARITH_TAC]);;
302 let POLY_ENTIRE = prove
303 (`!p q. (poly (p ** q) = poly []) <=>
304 (poly p = poly []) \/ (poly q = poly [])`,
305 REPEAT GEN_TAC THEN EQ_TAC THENL
306 [MESON_TAC[POLY_ENTIRE_LEMMA];
307 REWRITE_TAC[FUN_EQ_THM; POLY_MUL] THEN
309 ASM_REWRITE_TAC[COMPLEX_MUL_RZERO; COMPLEX_MUL_LZERO; poly]]);;
311 let POLY_MUL_LCANCEL = prove
312 (`!p q r. (poly (p ** q) = poly (p ** r)) <=>
313 (poly p = poly []) \/ (poly q = poly r)`,
315 (`!p q. (poly (p ++ neg q) = poly []) <=> (poly p = poly q)`,
316 REWRITE_TAC[FUN_EQ_THM; POLY_ADD; POLY_NEG; poly] THEN
317 REWRITE_TAC[SIMPLE_COMPLEX_ARITH `(p + --q = Cx(&0)) <=> (p = q)`]) in
319 (`!p q r. poly (p ** q ++ neg(p ** r)) = poly (p ** (q ++ neg(r)))`,
320 REWRITE_TAC[FUN_EQ_THM; POLY_ADD; POLY_NEG; POLY_MUL] THEN
321 SIMPLE_COMPLEX_ARITH_TAC) in
322 ONCE_REWRITE_TAC[GSYM lemma1] THEN
323 REWRITE_TAC[lemma2; POLY_ENTIRE] THEN
324 REWRITE_TAC[lemma1]);;
326 let POLY_EXP_EQ_0 = prove
327 (`!p n. (poly (p exp n) = poly []) <=> (poly p = poly []) /\ ~(n = 0)`,
328 REPEAT GEN_TAC THEN REWRITE_TAC[FUN_EQ_THM; poly] THEN
329 REWRITE_TAC[LEFT_AND_FORALL_THM] THEN AP_TERM_TAC THEN ABS_TAC THEN
330 SPEC_TAC(`n:num`,`n:num`) THEN INDUCT_TAC THEN
331 REWRITE_TAC[poly_exp; poly; COMPLEX_MUL_RZERO; COMPLEX_ADD_RID;
332 CX_INJ; REAL_OF_NUM_EQ; ARITH; NOT_SUC] THEN
333 ASM_REWRITE_TAC[POLY_MUL; poly; COMPLEX_ENTIRE] THEN
336 let POLY_PRIME_EQ_0 = prove
337 (`!a. ~(poly [a ; Cx(&1)] = poly [])`,
338 GEN_TAC THEN REWRITE_TAC[FUN_EQ_THM; poly] THEN
339 DISCH_THEN(MP_TAC o SPEC `Cx(&1) - a`) THEN
340 SIMPLE_COMPLEX_ARITH_TAC);;
342 let POLY_EXP_PRIME_EQ_0 = prove
343 (`!a n. ~(poly ([a ; Cx(&1)] exp n) = poly [])`,
344 MESON_TAC[POLY_EXP_EQ_0; POLY_PRIME_EQ_0]);;
346 (* ------------------------------------------------------------------------- *)
347 (* Can also prove a more "constructive" notion of polynomial being trivial. *)
348 (* ------------------------------------------------------------------------- *)
350 let POLY_ZERO_LEMMA = prove
351 (`!h t. (poly (CONS h t) = poly []) ==> (h = Cx(&0)) /\ (poly t = poly [])`,
352 let lemma = REWRITE_RULE[FUN_EQ_THM; poly] POLY_ROOTS_FINITE in
353 REPEAT GEN_TAC THEN REWRITE_TAC[FUN_EQ_THM; poly] THEN
354 ASM_CASES_TAC `h = Cx(&0)` THEN ASM_REWRITE_TAC[] THENL
355 [REWRITE_TAC[COMPLEX_ADD_LID];
356 DISCH_THEN(MP_TAC o SPEC `Cx(&0)`) THEN
357 POP_ASSUM MP_TAC THEN SIMPLE_COMPLEX_ARITH_TAC] THEN
358 CONV_TAC CONTRAPOS_CONV THEN
359 DISCH_THEN(MP_TAC o REWRITE_RULE[lemma]) THEN
360 DISCH_THEN(X_CHOOSE_THEN `N:num` (X_CHOOSE_TAC `i:num->complex`)) THEN
362 [`i:num->complex`; `N:num`; `\x. poly t x = Cx(&0)`] FINITE_LEMMA) THEN
363 ASM_REWRITE_TAC[] THEN DISCH_THEN(X_CHOOSE_TAC `a:real`) THEN
364 DISCH_THEN(MP_TAC o SPEC `Cx(abs(a) + &1)`) THEN
365 REWRITE_TAC[COMPLEX_ENTIRE; DE_MORGAN_THM] THEN CONJ_TAC THENL
366 [REWRITE_TAC[CX_INJ] THEN REAL_ARITH_TAC;
367 DISCH_THEN(MP_TAC o MATCH_MP
368 (ASSUME `!x. (poly t x = Cx(&0)) ==> norm(x) < a`)) THEN
369 REWRITE_TAC[COMPLEX_NORM_CX] THEN REAL_ARITH_TAC]);;
371 let POLY_ZERO = prove
372 (`!p. (poly p = poly []) <=> ALL (\c. c = Cx(&0)) p`,
373 LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[ALL] THEN EQ_TAC THENL
374 [DISCH_THEN(MP_TAC o MATCH_MP POLY_ZERO_LEMMA) THEN ASM_REWRITE_TAC[];
375 POP_ASSUM(SUBST1_TAC o SYM) THEN STRIP_TAC THEN
376 ASM_REWRITE_TAC[FUN_EQ_THM; poly] THEN SIMPLE_COMPLEX_ARITH_TAC]);;
378 (* ------------------------------------------------------------------------- *)
379 (* Basics of divisibility. *)
380 (* ------------------------------------------------------------------------- *)
382 let divides = new_definition
383 `p1 divides p2 <=> ?q. poly p2 = poly (p1 ** q)`;;
385 let POLY_PRIMES = prove
386 (`!a p q. [a; Cx(&1)] divides (p ** q) <=>
387 [a; Cx(&1)] divides p \/ [a; Cx(&1)] divides q`,
388 REPEAT GEN_TAC THEN REWRITE_TAC[divides; POLY_MUL; FUN_EQ_THM; poly] THEN
389 REWRITE_TAC[COMPLEX_MUL_RZERO; COMPLEX_ADD_RID; COMPLEX_MUL_RID] THEN
391 [DISCH_THEN(X_CHOOSE_THEN `r:complex list` (MP_TAC o SPEC `--a`)) THEN
392 REWRITE_TAC[COMPLEX_ENTIRE; GSYM complex_sub;
393 COMPLEX_SUB_REFL; COMPLEX_MUL_LZERO] THEN
394 DISCH_THEN DISJ_CASES_TAC THENL [DISJ1_TAC; DISJ2_TAC] THEN
395 (POP_ASSUM(MP_TAC o REWRITE_RULE[POLY_LINEAR_DIVIDES]) THEN
396 REWRITE_TAC[COMPLEX_NEG_NEG] THEN
397 DISCH_THEN(DISJ_CASES_THEN2 SUBST_ALL_TAC
398 (X_CHOOSE_THEN `s:complex list` SUBST_ALL_TAC)) THENL
399 [EXISTS_TAC `[]:complex list` THEN REWRITE_TAC[poly; COMPLEX_MUL_RZERO];
400 EXISTS_TAC `s:complex list` THEN GEN_TAC THEN
401 REWRITE_TAC[POLY_MUL; poly] THEN SIMPLE_COMPLEX_ARITH_TAC]);
402 DISCH_THEN(DISJ_CASES_THEN(X_CHOOSE_TAC `s:complex list`)) THEN
403 ASM_REWRITE_TAC[] THENL
404 [EXISTS_TAC `s ** q`; EXISTS_TAC `p ** s`] THEN
405 GEN_TAC THEN REWRITE_TAC[POLY_MUL] THEN SIMPLE_COMPLEX_ARITH_TAC]);;
407 let POLY_DIVIDES_REFL = prove
409 GEN_TAC THEN REWRITE_TAC[divides] THEN EXISTS_TAC `[Cx(&1)]` THEN
410 REWRITE_TAC[FUN_EQ_THM; POLY_MUL; poly] THEN SIMPLE_COMPLEX_ARITH_TAC);;
412 let POLY_DIVIDES_TRANS = prove
413 (`!p q r. p divides q /\ q divides r ==> p divides r`,
414 REPEAT GEN_TAC THEN REWRITE_TAC[divides] THEN
415 DISCH_THEN(CONJUNCTS_THEN MP_TAC) THEN
416 DISCH_THEN(X_CHOOSE_THEN `s:complex list` ASSUME_TAC) THEN
417 DISCH_THEN(X_CHOOSE_THEN `t:complex list` ASSUME_TAC) THEN
418 EXISTS_TAC `t ** s` THEN
419 ASM_REWRITE_TAC[FUN_EQ_THM; POLY_MUL; COMPLEX_MUL_ASSOC]);;
421 let POLY_DIVIDES_EXP = prove
422 (`!p m n. m <= n ==> (p exp m) divides (p exp n)`,
423 REPEAT GEN_TAC THEN REWRITE_TAC[LE_EXISTS] THEN
424 DISCH_THEN(X_CHOOSE_THEN `d:num` SUBST1_TAC) THEN
425 SPEC_TAC(`d:num`,`d:num`) THEN INDUCT_TAC THEN
426 REWRITE_TAC[ADD_CLAUSES; POLY_DIVIDES_REFL] THEN
427 MATCH_MP_TAC POLY_DIVIDES_TRANS THEN
428 EXISTS_TAC `p exp (m + d)` THEN ASM_REWRITE_TAC[] THEN
429 REWRITE_TAC[divides] THEN EXISTS_TAC `p:complex list` THEN
430 REWRITE_TAC[poly_exp; FUN_EQ_THM; POLY_MUL] THEN
431 SIMPLE_COMPLEX_ARITH_TAC);;
433 let POLY_EXP_DIVIDES = prove
434 (`!p q m n. (p exp n) divides q /\ m <= n ==> (p exp m) divides q`,
435 MESON_TAC[POLY_DIVIDES_TRANS; POLY_DIVIDES_EXP]);;
437 let POLY_DIVIDES_ADD = prove
438 (`!p q r. p divides q /\ p divides r ==> p divides (q ++ r)`,
439 REPEAT GEN_TAC THEN REWRITE_TAC[divides] THEN
440 DISCH_THEN(CONJUNCTS_THEN MP_TAC) THEN
441 DISCH_THEN(X_CHOOSE_THEN `s:complex list` ASSUME_TAC) THEN
442 DISCH_THEN(X_CHOOSE_THEN `t:complex list` ASSUME_TAC) THEN
443 EXISTS_TAC `t ++ s` THEN
444 ASM_REWRITE_TAC[FUN_EQ_THM; POLY_ADD; POLY_MUL] THEN
445 SIMPLE_COMPLEX_ARITH_TAC);;
447 let POLY_DIVIDES_SUB = prove
448 (`!p q r. p divides q /\ p divides (q ++ r) ==> p divides r`,
449 REPEAT GEN_TAC THEN REWRITE_TAC[divides] THEN
450 DISCH_THEN(CONJUNCTS_THEN MP_TAC) THEN
451 DISCH_THEN(X_CHOOSE_THEN `s:complex list` ASSUME_TAC) THEN
452 DISCH_THEN(X_CHOOSE_THEN `t:complex list` ASSUME_TAC) THEN
453 EXISTS_TAC `s ++ neg(t)` THEN
454 POP_ASSUM_LIST(MP_TAC o end_itlist CONJ) THEN
455 REWRITE_TAC[FUN_EQ_THM; POLY_ADD; POLY_MUL; POLY_NEG] THEN
456 DISCH_THEN(STRIP_ASSUME_TAC o GSYM) THEN
457 REWRITE_TAC[COMPLEX_ADD_LDISTRIB; COMPLEX_MUL_RNEG] THEN
458 ASM_REWRITE_TAC[] THEN SIMPLE_COMPLEX_ARITH_TAC);;
460 let POLY_DIVIDES_SUB2 = prove
461 (`!p q r. p divides r /\ p divides (q ++ r) ==> p divides q`,
462 REPEAT STRIP_TAC THEN MATCH_MP_TAC POLY_DIVIDES_SUB THEN
463 EXISTS_TAC `r:complex list` THEN ASM_REWRITE_TAC[] THEN
464 UNDISCH_TAC `p divides (q ++ r)` THEN
465 REWRITE_TAC[divides; POLY_ADD; FUN_EQ_THM; POLY_MUL] THEN
466 DISCH_THEN(X_CHOOSE_TAC `s:complex list`) THEN
467 EXISTS_TAC `s:complex list` THEN
468 X_GEN_TAC `x:complex` THEN POP_ASSUM(MP_TAC o SPEC `x:complex`) THEN
469 SIMPLE_COMPLEX_ARITH_TAC);;
471 let POLY_DIVIDES_ZERO = prove
472 (`!p q. (poly p = poly []) ==> q divides p`,
473 REPEAT GEN_TAC THEN DISCH_TAC THEN REWRITE_TAC[divides] THEN
474 EXISTS_TAC `[]:complex list` THEN
475 ASM_REWRITE_TAC[FUN_EQ_THM; POLY_MUL; poly; COMPLEX_MUL_RZERO]);;
477 (* ------------------------------------------------------------------------- *)
478 (* At last, we can consider the order of a root. *)
479 (* ------------------------------------------------------------------------- *)
481 let POLY_ORDER_EXISTS = prove
482 (`!a d. !p. (LENGTH p = d) /\ ~(poly p = poly [])
483 ==> ?n. ([--a; Cx(&1)] exp n) divides p /\
484 ~(([--a; Cx(&1)] exp (SUC n)) divides p)`,
486 (STRIP_ASSUME_TAC o prove_recursive_functions_exist num_RECURSION)
487 `(!p q. mulexp 0 p q = q) /\
488 (!p q n. mulexp (SUC n) p q = p ** (mulexp n p q))` THEN
490 `!d. !p. (LENGTH p = d) /\ ~(poly p = poly [])
491 ==> ?n q. (p = mulexp (n:num) [--a; Cx(&1)] q) /\
492 ~(poly q a = Cx(&0))`
495 [REWRITE_TAC[LENGTH_EQ_NIL] THEN MESON_TAC[]; ALL_TAC] THEN
496 X_GEN_TAC `p:complex list` THEN
497 ASM_CASES_TAC `poly p a = Cx(&0)` THENL
498 [STRIP_TAC THEN UNDISCH_TAC `poly p a = Cx(&0)` THEN
499 DISCH_THEN(MP_TAC o REWRITE_RULE[POLY_LINEAR_DIVIDES]) THEN
500 DISCH_THEN(DISJ_CASES_THEN MP_TAC) THENL [ASM_MESON_TAC[]; ALL_TAC] THEN
501 DISCH_THEN(X_CHOOSE_THEN `q:complex list` SUBST_ALL_TAC) THEN
503 `!p. (LENGTH p = d) /\ ~(poly p = poly [])
504 ==> ?n q. (p = mulexp (n:num) [--a; Cx(&1)] q) /\
505 ~(poly q a = Cx(&0))` THEN
506 DISCH_THEN(MP_TAC o SPEC `q:complex list`) THEN
507 RULE_ASSUM_TAC(REWRITE_RULE[POLY_LENGTH_MUL; POLY_ENTIRE;
508 DE_MORGAN_THM; SUC_INJ]) THEN
509 ASM_REWRITE_TAC[] THEN
510 DISCH_THEN(X_CHOOSE_THEN `n:num`
511 (X_CHOOSE_THEN `s:complex list` STRIP_ASSUME_TAC)) THEN
512 EXISTS_TAC `SUC n` THEN EXISTS_TAC `s:complex list` THEN
514 STRIP_TAC THEN EXISTS_TAC `0` THEN EXISTS_TAC `p:complex list` THEN
516 DISCH_TAC THEN REPEAT GEN_TAC THEN
517 DISCH_THEN(ANTE_RES_THEN MP_TAC) THEN
518 DISCH_THEN(X_CHOOSE_THEN `n:num`
519 (X_CHOOSE_THEN `s:complex list` STRIP_ASSUME_TAC)) THEN
520 EXISTS_TAC `n:num` THEN ASM_REWRITE_TAC[] THEN
521 REWRITE_TAC[divides] THEN CONJ_TAC THENL
522 [EXISTS_TAC `s:complex list` THEN
523 SPEC_TAC(`n:num`,`n:num`) THEN INDUCT_TAC THEN
524 ASM_REWRITE_TAC[poly_exp; FUN_EQ_THM; POLY_MUL; poly] THEN
525 SIMPLE_COMPLEX_ARITH_TAC;
526 DISCH_THEN(X_CHOOSE_THEN `r:complex list` MP_TAC) THEN
527 SPEC_TAC(`n:num`,`n:num`) THEN INDUCT_TAC THEN
528 ASM_REWRITE_TAC[] THENL
529 [UNDISCH_TAC `~(poly s a = Cx(&0))` THEN CONV_TAC CONTRAPOS_CONV THEN
530 REWRITE_TAC[] THEN DISCH_THEN SUBST1_TAC THEN
531 REWRITE_TAC[poly; poly_exp; POLY_MUL] THEN SIMPLE_COMPLEX_ARITH_TAC;
532 REWRITE_TAC[] THEN ONCE_ASM_REWRITE_TAC[] THEN
533 ONCE_REWRITE_TAC[poly_exp] THEN
534 REWRITE_TAC[GSYM POLY_MUL_ASSOC; POLY_MUL_LCANCEL] THEN
535 REWRITE_TAC[DE_MORGAN_THM] THEN CONJ_TAC THENL
536 [REWRITE_TAC[FUN_EQ_THM] THEN
537 DISCH_THEN(MP_TAC o SPEC `a + Cx(&1)`) THEN
538 REWRITE_TAC[poly] THEN SIMPLE_COMPLEX_ARITH_TAC;
539 DISCH_THEN(ANTE_RES_THEN MP_TAC) THEN REWRITE_TAC[]]]]]);;
541 let POLY_ORDER = prove
542 (`!p a. ~(poly p = poly [])
543 ==> ?!n. ([--a; Cx(&1)] exp n) divides p /\
544 ~(([--a; Cx(&1)] exp (SUC n)) divides p)`,
545 MESON_TAC[POLY_ORDER_EXISTS; POLY_EXP_DIVIDES; LE_SUC_LT; LT_CASES]);;
547 (* ------------------------------------------------------------------------- *)
548 (* Definition of order. *)
549 (* ------------------------------------------------------------------------- *)
551 let order = new_definition
552 `order a p = @n. ([--a; Cx(&1)] exp n) divides p /\
553 ~(([--a; Cx(&1)] exp (SUC n)) divides p)`;;
556 (`!p a n. ([--a; Cx(&1)] exp n) divides p /\
557 ~(([--a; Cx(&1)] exp (SUC n)) divides p) <=>
559 ~(poly p = poly [])`,
560 REPEAT GEN_TAC THEN REWRITE_TAC[order] THEN
561 EQ_TAC THEN STRIP_TAC THENL
562 [SUBGOAL_THEN `~(poly p = poly [])` ASSUME_TAC THENL
563 [FIRST_ASSUM(UNDISCH_TAC o check is_neg o concl) THEN
564 CONV_TAC CONTRAPOS_CONV THEN REWRITE_TAC[divides] THEN
565 DISCH_THEN SUBST1_TAC THEN EXISTS_TAC `[]:complex list` THEN
566 REWRITE_TAC[FUN_EQ_THM; POLY_MUL; poly; COMPLEX_MUL_RZERO];
567 ASM_REWRITE_TAC[] THEN CONV_TAC SYM_CONV THEN
568 MATCH_MP_TAC SELECT_UNIQUE THEN REWRITE_TAC[]];
569 ONCE_ASM_REWRITE_TAC[] THEN CONV_TAC SELECT_CONV] THEN
570 ASM_MESON_TAC[POLY_ORDER]);;
572 let ORDER_THM = prove
573 (`!p a. ~(poly p = poly [])
574 ==> ([--a; Cx(&1)] exp (order a p)) divides p /\
575 ~(([--a; Cx(&1)] exp (SUC(order a p))) divides p)`,
578 let ORDER_UNIQUE = prove
579 (`!p a n. ~(poly p = poly []) /\
580 ([--a; Cx(&1)] exp n) divides p /\
581 ~(([--a; Cx(&1)] exp (SUC n)) divides p)
582 ==> (n = order a p)`,
585 let ORDER_POLY = prove
586 (`!p q a. (poly p = poly q) ==> (order a p = order a q)`,
587 REPEAT STRIP_TAC THEN
588 ASM_REWRITE_TAC[order; divides; FUN_EQ_THM; POLY_MUL]);;
590 let ORDER_ROOT = prove
591 (`!p a. (poly p a = Cx(&0)) <=> (poly p = poly []) \/ ~(order a p = 0)`,
592 REPEAT GEN_TAC THEN ASM_CASES_TAC `poly p = poly []` THEN
593 ASM_REWRITE_TAC[poly] THEN EQ_TAC THENL
594 [DISCH_THEN(MP_TAC o REWRITE_RULE[POLY_LINEAR_DIVIDES]) THEN
595 ASM_CASES_TAC `p:complex list = []` THENL [ASM_MESON_TAC[]; ALL_TAC] THEN
596 ASM_REWRITE_TAC[] THEN
597 DISCH_THEN(X_CHOOSE_THEN `q:complex list` SUBST_ALL_TAC) THEN DISCH_TAC THEN
598 FIRST_ASSUM(MP_TAC o SPEC `a:complex` o MATCH_MP ORDER_THM) THEN
599 ASM_REWRITE_TAC[poly_exp; DE_MORGAN_THM] THEN DISJ2_TAC THEN
600 REWRITE_TAC[divides] THEN EXISTS_TAC `q:complex list` THEN
601 REWRITE_TAC[FUN_EQ_THM; POLY_MUL; poly] THEN SIMPLE_COMPLEX_ARITH_TAC;
603 FIRST_ASSUM(MP_TAC o SPEC `a:complex` o MATCH_MP ORDER_THM) THEN
604 UNDISCH_TAC `~(order a p = 0)` THEN
605 SPEC_TAC(`order a p`,`n:num`) THEN
606 INDUCT_TAC THEN ASM_REWRITE_TAC[poly_exp; NOT_SUC] THEN
607 DISCH_THEN(MP_TAC o CONJUNCT1) THEN REWRITE_TAC[divides] THEN
608 DISCH_THEN(X_CHOOSE_THEN `s:complex list` SUBST1_TAC) THEN
609 REWRITE_TAC[POLY_MUL; poly] THEN SIMPLE_COMPLEX_ARITH_TAC]);;
611 let ORDER_DIVIDES = prove
612 (`!p a n. ([--a; Cx(&1)] exp n) divides p <=>
613 (poly p = poly []) \/ n <= order a p`,
614 REPEAT GEN_TAC THEN ASM_CASES_TAC `poly p = poly []` THEN
615 ASM_REWRITE_TAC[] THENL
616 [ASM_REWRITE_TAC[divides] THEN EXISTS_TAC `[]:complex list` THEN
617 REWRITE_TAC[FUN_EQ_THM; POLY_MUL; poly; COMPLEX_MUL_RZERO];
618 ASM_MESON_TAC[ORDER_THM; POLY_EXP_DIVIDES; NOT_LE; LE_SUC_LT]]);;
620 let ORDER_DECOMP = prove
621 (`!p a. ~(poly p = poly [])
622 ==> ?q. (poly p = poly (([--a; Cx(&1)] exp (order a p)) ** q)) /\
623 ~([--a; Cx(&1)] divides q)`,
624 REPEAT STRIP_TAC THEN FIRST_ASSUM(MP_TAC o MATCH_MP ORDER_THM) THEN
625 DISCH_THEN(CONJUNCTS_THEN2 MP_TAC ASSUME_TAC o SPEC `a:complex`) THEN
626 DISCH_THEN(X_CHOOSE_TAC `q:complex list` o REWRITE_RULE[divides]) THEN
627 EXISTS_TAC `q:complex list` THEN ASM_REWRITE_TAC[] THEN
628 DISCH_THEN(X_CHOOSE_TAC `r: complex list` o REWRITE_RULE[divides]) THEN
629 UNDISCH_TAC `~([-- a; Cx(&1)] exp SUC (order a p) divides p)` THEN
630 ASM_REWRITE_TAC[] THEN REWRITE_TAC[divides] THEN
631 EXISTS_TAC `r:complex list` THEN
632 ASM_REWRITE_TAC[POLY_MUL; FUN_EQ_THM; poly_exp] THEN
633 SIMPLE_COMPLEX_ARITH_TAC);;
635 (* ------------------------------------------------------------------------- *)
636 (* Important composition properties of orders. *)
637 (* ------------------------------------------------------------------------- *)
639 let ORDER_MUL = prove
640 (`!a p q. ~(poly (p ** q) = poly []) ==>
641 (order a (p ** q) = order a p + order a q)`,
643 DISCH_THEN(fun th -> ASSUME_TAC th THEN MP_TAC th) THEN
644 REWRITE_TAC[POLY_ENTIRE; DE_MORGAN_THM] THEN STRIP_TAC THEN
645 SUBGOAL_THEN `(order a p + order a q = order a (p ** q)) /\
646 ~(poly (p ** q) = poly [])`
647 MP_TAC THENL [ALL_TAC; MESON_TAC[]] THEN
648 REWRITE_TAC[GSYM ORDER] THEN CONJ_TAC THENL
649 [MP_TAC(CONJUNCT1 (SPEC `a:complex`
650 (MATCH_MP ORDER_THM (ASSUME `~(poly p = poly [])`)))) THEN
651 DISCH_THEN(X_CHOOSE_TAC `r: complex list` o REWRITE_RULE[divides]) THEN
652 MP_TAC(CONJUNCT1 (SPEC `a:complex`
653 (MATCH_MP ORDER_THM (ASSUME `~(poly q = poly [])`)))) THEN
654 DISCH_THEN(X_CHOOSE_TAC `s: complex list` o REWRITE_RULE[divides]) THEN
655 REWRITE_TAC[divides; FUN_EQ_THM] THEN EXISTS_TAC `s ** r` THEN
656 ASM_REWRITE_TAC[POLY_MUL; POLY_EXP_ADD] THEN SIMPLE_COMPLEX_ARITH_TAC;
657 X_CHOOSE_THEN `r: complex list` STRIP_ASSUME_TAC
658 (SPEC `a:complex` (MATCH_MP ORDER_DECOMP
659 (ASSUME `~(poly p = poly [])`))) THEN
660 X_CHOOSE_THEN `s: complex list` STRIP_ASSUME_TAC
661 (SPEC `a:complex` (MATCH_MP ORDER_DECOMP
662 (ASSUME `~(poly q = poly [])`))) THEN
663 ASM_REWRITE_TAC[divides; FUN_EQ_THM; POLY_EXP_ADD; POLY_MUL; poly_exp] THEN
664 DISCH_THEN(X_CHOOSE_THEN `t:complex list` STRIP_ASSUME_TAC) THEN
665 SUBGOAL_THEN `[--a; Cx(&1)] divides (r ** s)` MP_TAC THENL
666 [ALL_TAC; ASM_REWRITE_TAC[POLY_PRIMES]] THEN
667 REWRITE_TAC[divides] THEN EXISTS_TAC `t:complex list` THEN
668 SUBGOAL_THEN `poly ([-- a; Cx(&1)] exp (order a p) ** r ** s) =
669 poly ([-- a; Cx(&1)] exp (order a p) **
670 ([-- a; Cx(&1)] ** t))`
672 [ALL_TAC; MESON_TAC[POLY_MUL_LCANCEL; POLY_EXP_PRIME_EQ_0]] THEN
673 SUBGOAL_THEN `poly ([-- a; Cx(&1)] exp (order a q) **
674 [-- a; Cx(&1)] exp (order a p) ** r ** s) =
675 poly ([-- a; Cx(&1)] exp (order a q) **
676 [-- a; Cx(&1)] exp (order a p) **
677 [-- a; Cx(&1)] ** t)`
679 [ALL_TAC; MESON_TAC[POLY_MUL_LCANCEL; POLY_EXP_PRIME_EQ_0]] THEN
680 REWRITE_TAC[FUN_EQ_THM; POLY_MUL; POLY_ADD] THEN
681 FIRST_ASSUM(UNDISCH_TAC o check is_forall o concl) THEN
682 REWRITE_TAC[COMPLEX_MUL_AC]]);;
684 (* ------------------------------------------------------------------------- *)
685 (* Normalization of a polynomial. *)
686 (* ------------------------------------------------------------------------- *)
688 let normalize = new_recursive_definition list_RECURSION
689 `(normalize [] = []) /\
690 (normalize (CONS h t) =
691 if normalize t = [] then if h = Cx(&0) then [] else [h]
692 else CONS h (normalize t))`;;
694 let POLY_NORMALIZE = prove
695 (`!p. poly (normalize p) = poly p`,
696 LIST_INDUCT_TAC THEN REWRITE_TAC[normalize; poly] THEN
697 ASM_CASES_TAC `h = Cx(&0)` THEN ASM_REWRITE_TAC[] THEN
698 COND_CASES_TAC THEN ASM_REWRITE_TAC[poly; FUN_EQ_THM] THEN
699 UNDISCH_TAC `poly (normalize t) = poly t` THEN
700 DISCH_THEN(SUBST1_TAC o SYM) THEN ASM_REWRITE_TAC[poly] THEN
701 REWRITE_TAC[COMPLEX_MUL_RZERO; COMPLEX_ADD_LID]);;
703 let LENGTH_NORMALIZE_LE = prove
704 (`!p. LENGTH(normalize p) <= LENGTH p`,
705 LIST_INDUCT_TAC THEN REWRITE_TAC[LENGTH; normalize; LE_REFL] THEN
706 COND_CASES_TAC THEN ASM_REWRITE_TAC[LENGTH; LE_SUC] THEN
707 COND_CASES_TAC THEN REWRITE_TAC[LENGTH] THEN ARITH_TAC);;
709 (* ------------------------------------------------------------------------- *)
710 (* The degree of a polynomial. *)
711 (* ------------------------------------------------------------------------- *)
713 let degree = new_definition
714 `degree p = PRE(LENGTH(normalize p))`;;
716 let DEGREE_ZERO = prove
717 (`!p. (poly p = poly []) ==> (degree p = 0)`,
718 REPEAT STRIP_TAC THEN REWRITE_TAC[degree] THEN
719 SUBGOAL_THEN `normalize p = []` SUBST1_TAC THENL
720 [POP_ASSUM MP_TAC THEN SPEC_TAC(`p:complex list`,`p:complex list`) THEN
721 REWRITE_TAC[POLY_ZERO] THEN
722 LIST_INDUCT_TAC THEN REWRITE_TAC[normalize; ALL] THEN
723 STRIP_TAC THEN ASM_REWRITE_TAC[] THEN
724 SUBGOAL_THEN `normalize t = []` (fun th -> REWRITE_TAC[th]) THEN
725 FIRST_ASSUM MATCH_MP_TAC THEN ASM_REWRITE_TAC[];
726 REWRITE_TAC[LENGTH; PRE]]);;
728 (* ------------------------------------------------------------------------- *)
729 (* Show that the degree is welldefined. *)
730 (* ------------------------------------------------------------------------- *)
732 let POLY_CONS_EQ = prove
733 (`(poly (CONS h1 t1) = poly (CONS h2 t2)) <=>
734 (h1 = h2) /\ (poly t1 = poly t2)`,
735 REWRITE_TAC[FUN_EQ_THM] THEN EQ_TAC THENL [ALL_TAC; SIMP_TAC[poly]] THEN
736 ONCE_REWRITE_TAC[SIMPLE_COMPLEX_ARITH `(a = b) <=> (a + --b = Cx(&0))`] THEN
737 REWRITE_TAC[GSYM POLY_NEG; GSYM POLY_ADD] THEN DISCH_TAC THEN
738 SUBGOAL_THEN `poly (CONS h1 t1 ++ neg(CONS h2 t2)) = poly []` MP_TAC THENL
739 [ASM_REWRITE_TAC[poly; FUN_EQ_THM]; ALL_TAC] THEN
740 REWRITE_TAC[poly_neg; poly_cmul; poly_add; NOT_CONS_NIL; HD; TL] THEN
741 DISCH_THEN(MP_TAC o MATCH_MP POLY_ZERO_LEMMA) THEN
742 SIMP_TAC[poly; COMPLEX_MUL_LNEG; COMPLEX_MUL_LID]);;
744 let POLY_NORMALIZE_ZERO = prove
745 (`!p. (poly p = poly []) <=> (normalize p = [])`,
746 REWRITE_TAC[POLY_ZERO] THEN
747 LIST_INDUCT_TAC THEN REWRITE_TAC[ALL; normalize] THEN
748 ASM_CASES_TAC `normalize t = []` THEN ASM_REWRITE_TAC[] THEN
749 REWRITE_TAC[NOT_CONS_NIL] THEN
750 COND_CASES_TAC THEN ASM_REWRITE_TAC[NOT_CONS_NIL]);;
752 let POLY_NORMALIZE_EQ_LEMMA = prove
753 (`!p q. (poly p = poly q) ==> (normalize p = normalize q)`,
754 LIST_INDUCT_TAC THENL
755 [MESON_TAC[POLY_NORMALIZE_ZERO]; ALL_TAC] THEN
756 LIST_INDUCT_TAC THENL
757 [MESON_TAC[POLY_NORMALIZE_ZERO]; ALL_TAC] THEN
758 REWRITE_TAC[POLY_CONS_EQ] THEN
759 STRIP_TAC THEN ASM_REWRITE_TAC[normalize] THEN
760 FIRST_X_ASSUM(MP_TAC o SPEC `t':complex list`) THEN ASM_REWRITE_TAC[] THEN
761 DISCH_THEN SUBST1_TAC THEN REFL_TAC);;
763 let POLY_NORMALIZE_EQ = prove
764 (`!p q. (poly p = poly q) <=> (normalize p = normalize q)`,
765 MESON_TAC[POLY_NORMALIZE_EQ_LEMMA; POLY_NORMALIZE]);;
767 let DEGREE_WELLDEF = prove
768 (`!p q. (poly p = poly q) ==> (degree p = degree q)`,
769 SIMP_TAC[degree; POLY_NORMALIZE_EQ]);;
771 (* ------------------------------------------------------------------------- *)
772 (* Degree of a product with a power of linear terms. *)
773 (* ------------------------------------------------------------------------- *)
775 let NORMALIZE_EQ = prove
776 (`!p. ~(LAST p = Cx(&0)) ==> (normalize p = p)`,
777 MATCH_MP_TAC list_INDUCT THEN REWRITE_TAC[NOT_CONS_NIL] THEN
778 REWRITE_TAC[normalize; LAST] THEN REPEAT GEN_TAC THEN
779 REPEAT(COND_CASES_TAC THEN ASM_SIMP_TAC[normalize]));;
781 let NORMAL_DEGREE = prove
782 (`!p. ~(LAST p = Cx(&0)) ==> (degree p = LENGTH p - 1)`,
783 SIMP_TAC[degree; NORMALIZE_EQ] THEN REPEAT STRIP_TAC THEN ARITH_TAC);;
785 let LAST_LINEAR_MUL_LEMMA = prove
787 LAST(a ## p ++ CONS x (b ## p)) = if p = [] then x else b * LAST(p)`,
789 REWRITE_TAC[poly_cmul; poly_add; LAST; HD; TL; NOT_CONS_NIL] THEN
791 SUBGOAL_THEN `~(a ## t ++ CONS (b * h) (b ## t) = [])`
793 [SPEC_TAC(`t:complex list`,`t:complex list`) THEN
794 LIST_INDUCT_TAC THEN REWRITE_TAC[poly_cmul; poly_add; NOT_CONS_NIL];
796 ASM_REWRITE_TAC[] THEN COND_CASES_TAC THEN ASM_REWRITE_TAC[]);;
798 let LAST_LINEAR_MUL = prove
799 (`!p. ~(p = []) ==> (LAST([a; Cx(&1)] ** p) = LAST p)`,
800 SIMP_TAC[poly_mul; NOT_CONS_NIL; LAST_LINEAR_MUL_LEMMA; COMPLEX_MUL_LID]);;
802 let NORMAL_NORMALIZE = prove
803 (`!p. ~(normalize p = []) ==> ~(LAST(normalize p) = Cx(&0))`,
804 LIST_INDUCT_TAC THEN REWRITE_TAC[normalize] THEN
805 POP_ASSUM MP_TAC THEN ASM_CASES_TAC `normalize t = []` THEN
806 ASM_REWRITE_TAC[LAST; NOT_CONS_NIL] THEN
807 COND_CASES_TAC THEN ASM_REWRITE_TAC[LAST]);;
809 let LINEAR_MUL_DEGREE = prove
810 (`!p a. ~(poly p = poly []) ==> (degree([a; Cx(&1)] ** p) = degree(p) + 1)`,
811 REPEAT STRIP_TAC THEN
812 SUBGOAL_THEN `degree([a; Cx(&1)] ** normalize p) = degree(normalize p) + 1`
814 [FIRST_ASSUM(ASSUME_TAC o
815 GEN_REWRITE_RULE RAND_CONV [POLY_NORMALIZE_ZERO]) THEN
816 FIRST_ASSUM(MP_TAC o MATCH_MP NORMAL_NORMALIZE) THEN
817 FIRST_ASSUM(MP_TAC o MATCH_MP LAST_LINEAR_MUL) THEN
818 SIMP_TAC[NORMAL_DEGREE] THEN REPEAT STRIP_TAC THEN
819 SUBST1_TAC(SYM(SPEC `a:complex` COMPLEX_NEG_NEG)) THEN
820 REWRITE_TAC[POLY_LENGTH_MUL] THEN
821 UNDISCH_TAC `~(normalize p = [])` THEN
822 SPEC_TAC(`normalize p`,`p:complex list`) THEN
823 LIST_INDUCT_TAC THEN REWRITE_TAC[NOT_CONS_NIL; LENGTH] THEN ARITH_TAC;
824 MATCH_MP_TAC EQ_IMP THEN BINOP_TAC THEN
825 TRY(AP_THM_TAC THEN AP_TERM_TAC) THEN MATCH_MP_TAC DEGREE_WELLDEF THEN
826 REWRITE_TAC[FUN_EQ_THM; POLY_MUL; POLY_NORMALIZE]]);;
828 let LINEAR_POW_MUL_DEGREE = prove
829 (`!n a p. degree([a; Cx(&1)] exp n ** p) =
830 if poly p = poly [] then 0 else degree p + n`,
831 INDUCT_TAC THEN REWRITE_TAC[poly_exp] THENL
832 [GEN_TAC THEN COND_CASES_TAC THEN ASM_REWRITE_TAC[] THENL
833 [MATCH_MP_TAC EQ_TRANS THEN EXISTS_TAC `degree(p)` THEN CONJ_TAC THENL
834 [MATCH_MP_TAC DEGREE_WELLDEF THEN
835 REWRITE_TAC[FUN_EQ_THM; POLY_MUL; poly; COMPLEX_MUL_RZERO;
836 COMPLEX_ADD_RID; COMPLEX_MUL_LID];
837 MATCH_MP_TAC EQ_TRANS THEN EXISTS_TAC `degree []` THEN CONJ_TAC THENL
838 [MATCH_MP_TAC DEGREE_WELLDEF THEN ASM_REWRITE_TAC[];
839 REWRITE_TAC[degree; LENGTH; normalize; ARITH]]];
840 REWRITE_TAC[ADD_CLAUSES] THEN MATCH_MP_TAC DEGREE_WELLDEF THEN
841 REWRITE_TAC[FUN_EQ_THM; POLY_MUL; poly; COMPLEX_MUL_RZERO;
842 COMPLEX_ADD_RID; COMPLEX_MUL_LID]];
844 REPEAT GEN_TAC THEN MATCH_MP_TAC EQ_TRANS THEN
845 EXISTS_TAC `degree([a; Cx (&1)] exp n ** ([a; Cx (&1)] ** p))` THEN
847 [MATCH_MP_TAC DEGREE_WELLDEF THEN
848 REWRITE_TAC[FUN_EQ_THM; POLY_MUL; COMPLEX_MUL_AC]; ALL_TAC] THEN
849 ASM_REWRITE_TAC[POLY_ENTIRE] THEN
850 ASM_CASES_TAC `poly p = poly []` THEN ASM_REWRITE_TAC[] THEN
851 ASM_SIMP_TAC[LINEAR_MUL_DEGREE] THEN
852 SUBGOAL_THEN `~(poly [a; Cx (&1)] = poly [])`
853 (fun th -> REWRITE_TAC[th] THEN ARITH_TAC) THEN
854 REWRITE_TAC[POLY_NORMALIZE_EQ] THEN
855 REWRITE_TAC[normalize; CX_INJ; REAL_OF_NUM_EQ; ARITH; NOT_CONS_NIL]);;
857 (* ------------------------------------------------------------------------- *)
858 (* Show that the order of a root (or nonroot!) is bounded by degree. *)
859 (* ------------------------------------------------------------------------- *)
861 let ORDER_DEGREE = prove
862 (`!a p. ~(poly p = poly []) ==> order a p <= degree p`,
863 REPEAT STRIP_TAC THEN
864 FIRST_ASSUM(MP_TAC o SPEC `a:complex` o MATCH_MP ORDER_THM) THEN
865 DISCH_THEN(MP_TAC o REWRITE_RULE[divides] o CONJUNCT1) THEN
866 DISCH_THEN(X_CHOOSE_THEN `q:complex list` ASSUME_TAC) THEN
867 FIRST_ASSUM(SUBST1_TAC o MATCH_MP DEGREE_WELLDEF) THEN
868 ASM_REWRITE_TAC[LINEAR_POW_MUL_DEGREE] THEN
869 FIRST_X_ASSUM(MP_TAC o GEN_REWRITE_RULE I [FUN_EQ_THM]) THEN
870 COND_CASES_TAC THEN ASM_REWRITE_TAC[POLY_MUL] THENL
871 [UNDISCH_TAC `~(poly p = poly [])` THEN
872 SIMP_TAC[FUN_EQ_THM; POLY_MUL; poly; COMPLEX_MUL_RZERO];
873 DISCH_TAC THEN ARITH_TAC]);;
875 (* ------------------------------------------------------------------------- *)
876 (* Tidier versions of finiteness of roots. *)
877 (* ------------------------------------------------------------------------- *)
879 let POLY_ROOTS_FINITE_SET = prove
880 (`!p. ~(poly p = poly []) ==> FINITE { x | poly p x = Cx(&0)}`,
881 GEN_TAC THEN REWRITE_TAC[POLY_ROOTS_FINITE] THEN
882 DISCH_THEN(X_CHOOSE_THEN `N:num` MP_TAC) THEN
883 DISCH_THEN(X_CHOOSE_THEN `i:num->complex` ASSUME_TAC) THEN
884 MATCH_MP_TAC FINITE_SUBSET THEN
885 EXISTS_TAC `{x:complex | ?n:num. n < N /\ (x = i n)}` THEN
887 [SPEC_TAC(`N:num`,`N:num`) THEN POP_ASSUM_LIST(K ALL_TAC) THEN
889 [SUBGOAL_THEN `{x:complex | ?n. n < 0 /\ (x = i n)} = {}`
890 (fun th -> REWRITE_TAC[th; FINITE_RULES]) THEN
891 REWRITE_TAC[EXTENSION; IN_ELIM_THM; NOT_IN_EMPTY; LT];
892 SUBGOAL_THEN `{x:complex | ?n. n < SUC N /\ (x = i n)} =
893 (i N) INSERT {x:complex | ?n. n < N /\ (x = i n)}`
895 [REWRITE_TAC[EXTENSION; IN_ELIM_THM; IN_INSERT; LT] THEN MESON_TAC[];
896 MATCH_MP_TAC(CONJUNCT2 FINITE_RULES) THEN ASM_REWRITE_TAC[]]];
897 ASM_REWRITE_TAC[SUBSET; IN_ELIM_THM]]);;
899 (* ------------------------------------------------------------------------- *)
900 (* Conversions to perform operations if coefficients are rational constants. *)
901 (* ------------------------------------------------------------------------- *)
903 let COMPLEX_RAT_MUL_CONV =
904 GEN_REWRITE_CONV I [GSYM CX_MUL] THENC RAND_CONV REAL_RAT_MUL_CONV;;
906 let COMPLEX_RAT_ADD_CONV =
907 GEN_REWRITE_CONV I [GSYM CX_ADD] THENC RAND_CONV REAL_RAT_ADD_CONV;;
909 let COMPLEX_RAT_EQ_CONV =
910 GEN_REWRITE_CONV I [CX_INJ] THENC REAL_RAT_EQ_CONV;;
913 let cmul_conv0 = GEN_REWRITE_CONV I [CONJUNCT1 poly_cmul]
914 and cmul_conv1 = GEN_REWRITE_CONV I [CONJUNCT2 poly_cmul] in
915 let rec POLY_CMUL_CONV tm =
918 LAND_CONV COMPLEX_RAT_MUL_CONV THENC
919 RAND_CONV POLY_CMUL_CONV)) tm in
923 let add_conv0 = GEN_REWRITE_CONV I (butlast (CONJUNCTS POLY_ADD_CLAUSES))
924 and add_conv1 = GEN_REWRITE_CONV I [last (CONJUNCTS POLY_ADD_CLAUSES)] in
925 let rec POLY_ADD_CONV tm =
928 LAND_CONV COMPLEX_RAT_ADD_CONV THENC
929 RAND_CONV POLY_ADD_CONV)) tm in
933 let mul_conv0 = GEN_REWRITE_CONV I [CONJUNCT1 POLY_MUL_CLAUSES]
934 and mul_conv1 = GEN_REWRITE_CONV I [CONJUNCT1(CONJUNCT2 POLY_MUL_CLAUSES)]
935 and mul_conv2 = GEN_REWRITE_CONV I [CONJUNCT2(CONJUNCT2 POLY_MUL_CLAUSES)] in
936 let rec POLY_MUL_CONV tm =
938 (mul_conv1 THENC POLY_CMUL_CONV) ORELSEC
940 LAND_CONV POLY_CMUL_CONV THENC
941 RAND_CONV(RAND_CONV POLY_MUL_CONV) THENC
942 POLY_ADD_CONV)) tm in
945 let POLY_NORMALIZE_CONV =
947 (`normalize (CONS h t) =
948 (\n. if n = [] then if h = Cx(&0) then [] else [h] else CONS h n)
950 REWRITE_TAC[normalize]) in
951 let norm_conv0 = GEN_REWRITE_CONV I [CONJUNCT1 normalize]
952 and norm_conv1 = GEN_REWRITE_CONV I [pth]
953 and norm_conv2 = GEN_REWRITE_CONV DEPTH_CONV
954 [COND_CLAUSES; NOT_CONS_NIL; EQT_INTRO(SPEC_ALL EQ_REFL)] in
955 let rec POLY_NORMALIZE_CONV tm =
958 RAND_CONV POLY_NORMALIZE_CONV THENC
960 RATOR_CONV(RAND_CONV(RATOR_CONV(LAND_CONV COMPLEX_RAT_EQ_CONV))) THENC
962 POLY_NORMALIZE_CONV;;
964 (* ------------------------------------------------------------------------- *)
965 (* Now we're finished with polynomials... *)
966 (* ------------------------------------------------------------------------- *)
968 (************** keep this for now
970 do_list reduce_interface
971 ["divides",`poly_divides:complex list->complex list->bool`;
972 "exp",`poly_exp:complex list -> num -> complex list`;
973 "diff",`poly_diff:complex list->complex list`];;
975 unparse_as_infix "exp";;