1 (* ========================================================================= *)
2 (* The type "real^2" regarded as the complex numbers. *)
4 (* (c) Copyright, John Harrison 1998-2008 *)
5 (* (c) Copyright, Valentina Bruno 2010 *)
6 (* ========================================================================= *)
8 needs "Multivariate/integration.ml";;
10 new_type_abbrev("complex",`:real^2`);;
12 let prioritize_complex() =
13 overload_interface("--",`vector_neg:complex->complex`);
14 overload_interface("+",`vector_add:complex->complex->complex`);
15 overload_interface("-",`vector_sub:complex->complex->complex`);
16 overload_interface("*",`complex_mul:complex->complex->complex`);
17 overload_interface("/",`complex_div:complex->complex->complex`);
18 overload_interface("pow",`complex_pow:complex->num->complex`);
19 overload_interface("inv",`complex_inv:complex->complex`);;
21 prioritize_complex();;
23 (* ------------------------------------------------------------------------- *)
24 (* Real and imaginary parts of a number. *)
25 (* ------------------------------------------------------------------------- *)
27 let RE_DEF = new_definition
28 `Re(z:complex) = z$1`;;
30 let IM_DEF = new_definition
31 `Im(z:complex) = z$2`;;
33 (* ------------------------------------------------------------------------- *)
34 (* Real injection and imaginary unit. *)
35 (* ------------------------------------------------------------------------- *)
37 let complex = new_definition
38 `complex(x,y) = vector[x;y]:complex`;;
40 let CX_DEF = new_definition
41 `Cx(a) = complex(a,&0)`;;
43 let ii = new_definition
44 `ii = complex(&0,&1)`;;
46 (* ------------------------------------------------------------------------- *)
47 (* Complex multiplication. *)
48 (* ------------------------------------------------------------------------- *)
50 let complex_mul = new_definition
51 `w * z = complex(Re(w) * Re(z) - Im(w) * Im(z),
52 Re(w) * Im(z) + Im(w) * Re(z))`;;
54 let complex_inv = new_definition
55 `inv(z) = complex(Re(z) / (Re(z) pow 2 + Im(z) pow 2),
56 --(Im(z)) / (Re(z) pow 2 + Im(z) pow 2))`;;
58 let complex_div = new_definition
59 `w / z = w * inv(z)`;;
61 let complex_pow = define
62 `(x pow 0 = Cx(&1)) /\
63 (!n. x pow (SUC n) = x * x pow n)`;;
65 (* ------------------------------------------------------------------------- *)
66 (* Various handy rewrites. *)
67 (* ------------------------------------------------------------------------- *)
70 (`(Re(complex(x,y)) = x)`,
71 REWRITE_TAC[RE_DEF; complex; VECTOR_2]);;
74 (`Im(complex(x,y)) = y`,
75 REWRITE_TAC[IM_DEF; complex; VECTOR_2]);;
77 let COMPLEX_EQ = prove
78 (`!w z. (w = z) <=> (Re(w) = Re(z)) /\ (Im(w) = Im(z))`,
79 SIMP_TAC[CART_EQ; FORALL_2; DIMINDEX_2; RE_DEF; IM_DEF]);;
82 (`!z. complex(Re(z),Im(z)) = z`,
83 REWRITE_TAC[COMPLEX_EQ; RE; IM]);;
85 let COMPLEX_EQ_0 = prove
86 (`z = Cx(&0) <=> Re(z) pow 2 + Im(z) pow 2 = &0`,
87 REWRITE_TAC[COMPLEX_EQ; CX_DEF; RE; IM] THEN
88 EQ_TAC THEN SIMP_TAC[] THEN CONV_TAC REAL_RAT_REDUCE_CONV THEN
89 DISCH_THEN(MP_TAC o MATCH_MP (REAL_ARITH
90 `!x y:real. x + y = &0 ==> &0 <= x /\ &0 <= y ==> x = &0 /\ y = &0`)) THEN
91 REWRITE_TAC[REAL_POW_2; REAL_LE_SQUARE; REAL_ENTIRE]);;
93 let FORALL_COMPLEX = prove
94 (`(!z. P z) <=> (!x y. P(complex(x,y)))`,
97 let EXISTS_COMPLEX = prove
98 (`(?z. P z) <=> (?x y. P(complex(x,y)))`,
101 (* ------------------------------------------------------------------------- *)
102 (* Pseudo-definitions of other general vector concepts over R^2. *)
103 (* ------------------------------------------------------------------------- *)
105 let complex_neg = prove
106 (`--z = complex(--(Re(z)),--(Im(z)))`,
107 REWRITE_TAC[COMPLEX_EQ; RE; IM] THEN REWRITE_TAC[RE_DEF; IM_DEF] THEN
108 SIMP_TAC[VECTOR_NEG_COMPONENT; DIMINDEX_2; ARITH]);;
110 let complex_add = prove
111 (`w + z = complex(Re(w) + Re(z),Im(w) + Im(z))`,
112 REWRITE_TAC[COMPLEX_EQ; RE; IM] THEN REWRITE_TAC[RE_DEF; IM_DEF] THEN
113 SIMP_TAC[VECTOR_ADD_COMPONENT; DIMINDEX_2; ARITH]);;
115 let complex_sub = VECTOR_ARITH `(w:complex) - z = w + --z`;;
117 let complex_norm = prove
118 (`norm(z) = sqrt(Re(z) pow 2 + Im(z) pow 2)`,
119 REWRITE_TAC[vector_norm; dot; RE_DEF; IM_DEF; SUM_2; DIMINDEX_2] THEN
120 AP_TERM_TAC THEN REAL_ARITH_TAC);;
122 let COMPLEX_SQNORM = prove
123 (`norm(z) pow 2 = Re(z) pow 2 + Im(z) pow 2`,
124 REWRITE_TAC[NORM_POW_2; dot; RE_DEF; IM_DEF; SUM_2; DIMINDEX_2] THEN
127 (* ------------------------------------------------------------------------- *)
128 (* Crude tactic to automate very simple algebraic equivalences. *)
129 (* ------------------------------------------------------------------------- *)
131 let SIMPLE_COMPLEX_ARITH_TAC =
132 REWRITE_TAC[COMPLEX_EQ; RE; IM; CX_DEF;
133 complex_add; complex_neg; complex_sub; complex_mul;
134 complex_inv; complex_div] THEN
135 CONV_TAC REAL_FIELD;;
137 let SIMPLE_COMPLEX_ARITH tm = prove(tm,SIMPLE_COMPLEX_ARITH_TAC);;
139 (* ------------------------------------------------------------------------- *)
140 (* Basic algebraic properties that can be proved automatically by this. *)
141 (* ------------------------------------------------------------------------- *)
143 let COMPLEX_ADD_SYM = prove
144 (`!x y. x + y = y + x`,
145 SIMPLE_COMPLEX_ARITH_TAC);;
147 let COMPLEX_ADD_ASSOC = prove
148 (`!x y z. x + y + z = (x + y) + z`,
149 SIMPLE_COMPLEX_ARITH_TAC);;
151 let COMPLEX_ADD_LID = prove
152 (`!x. Cx(&0) + x = x`,
153 SIMPLE_COMPLEX_ARITH_TAC);;
155 let COMPLEX_ADD_LINV = prove
156 (`!x. --x + x = Cx(&0)`,
157 SIMPLE_COMPLEX_ARITH_TAC);;
159 let COMPLEX_MUL_SYM = prove
160 (`!x y. x * y = y * x`,
161 SIMPLE_COMPLEX_ARITH_TAC);;
163 let COMPLEX_MUL_ASSOC = prove
164 (`!x y z. x * y * z = (x * y) * z`,
165 SIMPLE_COMPLEX_ARITH_TAC);;
167 let COMPLEX_MUL_LID = prove
168 (`!x. Cx(&1) * x = x`,
169 SIMPLE_COMPLEX_ARITH_TAC);;
171 let COMPLEX_ADD_LDISTRIB = prove
172 (`!x y z. x * (y + z) = x * y + x * z`,
173 SIMPLE_COMPLEX_ARITH_TAC);;
175 let COMPLEX_ADD_AC = prove
176 (`(m + n = n + m) /\ ((m + n) + p = m + n + p) /\ (m + n + p = n + m + p)`,
177 SIMPLE_COMPLEX_ARITH_TAC);;
179 let COMPLEX_MUL_AC = prove
180 (`(m * n = n * m) /\ ((m * n) * p = m * n * p) /\ (m * n * p = n * m * p)`,
181 SIMPLE_COMPLEX_ARITH_TAC);;
183 let COMPLEX_ADD_RID = prove
184 (`!x. x + Cx(&0) = x`,
185 SIMPLE_COMPLEX_ARITH_TAC);;
187 let COMPLEX_MUL_RID = prove
188 (`!x. x * Cx(&1) = x`,
189 SIMPLE_COMPLEX_ARITH_TAC);;
191 let COMPLEX_ADD_RINV = prove
192 (`!x. x + --x = Cx(&0)`,
193 SIMPLE_COMPLEX_ARITH_TAC);;
195 let COMPLEX_ADD_RDISTRIB = prove
196 (`!x y z. (x + y) * z = x * z + y * z`,
197 SIMPLE_COMPLEX_ARITH_TAC);;
199 let COMPLEX_EQ_ADD_LCANCEL = prove
200 (`!x y z. (x + y = x + z) <=> (y = z)`,
201 SIMPLE_COMPLEX_ARITH_TAC);;
203 let COMPLEX_EQ_ADD_RCANCEL = prove
204 (`!x y z. (x + z = y + z) <=> (x = y)`,
205 SIMPLE_COMPLEX_ARITH_TAC);;
207 let COMPLEX_MUL_RZERO = prove
208 (`!x. x * Cx(&0) = Cx(&0)`,
209 SIMPLE_COMPLEX_ARITH_TAC);;
211 let COMPLEX_MUL_LZERO = prove
212 (`!x. Cx(&0) * x = Cx(&0)`,
213 SIMPLE_COMPLEX_ARITH_TAC);;
215 let COMPLEX_NEG_NEG = prove
217 SIMPLE_COMPLEX_ARITH_TAC);;
219 let COMPLEX_MUL_RNEG = prove
220 (`!x y. x * --y = --(x * y)`,
221 SIMPLE_COMPLEX_ARITH_TAC);;
223 let COMPLEX_MUL_LNEG = prove
224 (`!x y. --x * y = --(x * y)`,
225 SIMPLE_COMPLEX_ARITH_TAC);;
227 let COMPLEX_NEG_ADD = prove
228 (`!x y. --(x + y) = --x + --y`,
229 SIMPLE_COMPLEX_ARITH_TAC);;
231 let COMPLEX_NEG_0 = prove
232 (`--Cx(&0) = Cx(&0)`,
233 SIMPLE_COMPLEX_ARITH_TAC);;
235 let COMPLEX_EQ_ADD_LCANCEL_0 = prove
236 (`!x y. (x + y = x) <=> (y = Cx(&0))`,
237 SIMPLE_COMPLEX_ARITH_TAC);;
239 let COMPLEX_EQ_ADD_RCANCEL_0 = prove
240 (`!x y. (x + y = y) <=> (x = Cx(&0))`,
241 SIMPLE_COMPLEX_ARITH_TAC);;
243 let COMPLEX_LNEG_UNIQ = prove
244 (`!x y. (x + y = Cx(&0)) <=> (x = --y)`,
245 SIMPLE_COMPLEX_ARITH_TAC);;
247 let COMPLEX_RNEG_UNIQ = prove
248 (`!x y. (x + y = Cx(&0)) <=> (y = --x)`,
249 SIMPLE_COMPLEX_ARITH_TAC);;
251 let COMPLEX_NEG_LMUL = prove
252 (`!x y. --(x * y) = --x * y`,
253 SIMPLE_COMPLEX_ARITH_TAC);;
255 let COMPLEX_NEG_RMUL = prove
256 (`!x y. --(x * y) = x * --y`,
257 SIMPLE_COMPLEX_ARITH_TAC);;
259 let COMPLEX_NEG_MUL2 = prove
260 (`!x y. --x * --y = x * y`,
261 SIMPLE_COMPLEX_ARITH_TAC);;
263 let COMPLEX_SUB_ADD = prove
264 (`!x y. x - y + y = x`,
265 SIMPLE_COMPLEX_ARITH_TAC);;
267 let COMPLEX_SUB_ADD2 = prove
268 (`!x y. y + x - y = x`,
269 SIMPLE_COMPLEX_ARITH_TAC);;
271 let COMPLEX_SUB_REFL = prove
272 (`!x. x - x = Cx(&0)`,
273 SIMPLE_COMPLEX_ARITH_TAC);;
275 let COMPLEX_SUB_0 = prove
276 (`!x y. (x - y = Cx(&0)) <=> (x = y)`,
277 SIMPLE_COMPLEX_ARITH_TAC);;
279 let COMPLEX_NEG_EQ_0 = prove
280 (`!x. (--x = Cx(&0)) <=> (x = Cx(&0))`,
281 SIMPLE_COMPLEX_ARITH_TAC);;
283 let COMPLEX_NEG_SUB = prove
284 (`!x y. --(x - y) = y - x`,
285 SIMPLE_COMPLEX_ARITH_TAC);;
287 let COMPLEX_ADD_SUB = prove
288 (`!x y. (x + y) - x = y`,
289 SIMPLE_COMPLEX_ARITH_TAC);;
291 let COMPLEX_NEG_EQ = prove
292 (`!x y. (--x = y) <=> (x = --y)`,
293 SIMPLE_COMPLEX_ARITH_TAC);;
295 let COMPLEX_NEG_MINUS1 = prove
296 (`!x. --x = --Cx(&1) * x`,
297 SIMPLE_COMPLEX_ARITH_TAC);;
299 let COMPLEX_SUB_SUB = prove
300 (`!x y. x - y - x = --y`,
301 SIMPLE_COMPLEX_ARITH_TAC);;
303 let COMPLEX_ADD2_SUB2 = prove
304 (`!a b c d. (a + b) - (c + d) = a - c + b - d`,
305 SIMPLE_COMPLEX_ARITH_TAC);;
307 let COMPLEX_SUB_LZERO = prove
308 (`!x. Cx(&0) - x = --x`,
309 SIMPLE_COMPLEX_ARITH_TAC);;
311 let COMPLEX_SUB_RZERO = prove
312 (`!x. x - Cx(&0) = x`,
313 SIMPLE_COMPLEX_ARITH_TAC);;
315 let COMPLEX_SUB_LNEG = prove
316 (`!x y. --x - y = --(x + y)`,
317 SIMPLE_COMPLEX_ARITH_TAC);;
319 let COMPLEX_SUB_RNEG = prove
320 (`!x y. x - --y = x + y`,
321 SIMPLE_COMPLEX_ARITH_TAC);;
323 let COMPLEX_SUB_NEG2 = prove
324 (`!x y. --x - --y = y - x`,
325 SIMPLE_COMPLEX_ARITH_TAC);;
327 let COMPLEX_SUB_TRIANGLE = prove
328 (`!a b c. a - b + b - c = a - c`,
329 SIMPLE_COMPLEX_ARITH_TAC);;
331 let COMPLEX_EQ_SUB_LADD = prove
332 (`!x y z. (x = y - z) <=> (x + z = y)`,
333 SIMPLE_COMPLEX_ARITH_TAC);;
335 let COMPLEX_EQ_SUB_RADD = prove
336 (`!x y z. (x - y = z) <=> (x = z + y)`,
337 SIMPLE_COMPLEX_ARITH_TAC);;
339 let COMPLEX_SUB_SUB2 = prove
340 (`!x y. x - (x - y) = y`,
341 SIMPLE_COMPLEX_ARITH_TAC);;
343 let COMPLEX_ADD_SUB2 = prove
344 (`!x y. x - (x + y) = --y`,
345 SIMPLE_COMPLEX_ARITH_TAC);;
347 let COMPLEX_DIFFSQ = prove
348 (`!x y. (x + y) * (x - y) = x * x - y * y`,
349 SIMPLE_COMPLEX_ARITH_TAC);;
351 let COMPLEX_EQ_NEG2 = prove
352 (`!x y. (--x = --y) <=> (x = y)`,
353 SIMPLE_COMPLEX_ARITH_TAC);;
355 let COMPLEX_SUB_LDISTRIB = prove
356 (`!x y z. x * (y - z) = x * y - x * z`,
357 SIMPLE_COMPLEX_ARITH_TAC);;
359 let COMPLEX_SUB_RDISTRIB = prove
360 (`!x y z. (x - y) * z = x * z - y * z`,
361 SIMPLE_COMPLEX_ARITH_TAC);;
363 let COMPLEX_MUL_2 = prove
364 (`!x. Cx(&2) * x = x + x`,
365 SIMPLE_COMPLEX_ARITH_TAC);;
367 (* ------------------------------------------------------------------------- *)
368 (* Sometimes here we need to tweak non-zeroness assertions. *)
369 (* ------------------------------------------------------------------------- *)
373 REWRITE_TAC[ii] THEN SIMPLE_COMPLEX_ARITH_TAC);;
375 let COMPLEX_MUL_LINV = prove
376 (`!z. ~(z = Cx(&0)) ==> (inv(z) * z = Cx(&1))`,
377 REWRITE_TAC[COMPLEX_EQ_0] THEN SIMPLE_COMPLEX_ARITH_TAC);;
379 let COMPLEX_ENTIRE = prove
380 (`!x y. (x * y = Cx(&0)) <=> (x = Cx(&0)) \/ (y = Cx(&0))`,
381 REWRITE_TAC[COMPLEX_EQ_0] THEN SIMPLE_COMPLEX_ARITH_TAC);;
383 let COMPLEX_MUL_RINV = prove
384 (`!z. ~(z = Cx(&0)) ==> (z * inv(z) = Cx(&1))`,
385 REWRITE_TAC[COMPLEX_EQ_0] THEN SIMPLE_COMPLEX_ARITH_TAC);;
387 let COMPLEX_DIV_REFL = prove
388 (`!x. ~(x = Cx(&0)) ==> (x / x = Cx(&1))`,
389 REWRITE_TAC[COMPLEX_EQ_0] THEN SIMPLE_COMPLEX_ARITH_TAC);;
391 (* ------------------------------------------------------------------------- *)
392 (* Homomorphic embedding properties for Cx mapping. *)
393 (* ------------------------------------------------------------------------- *)
396 (`!x y. (Cx(x) = Cx(y)) <=> (x = y)`,
397 REWRITE_TAC[CX_DEF; COMPLEX_EQ; RE; IM]);;
400 (`!x. Cx(--x) = --(Cx(x))`,
401 REWRITE_TAC[CX_DEF; complex_neg; RE; IM; REAL_NEG_0]);;
404 (`!x y. Cx(x + y) = Cx(x) + Cx(y)`,
405 REWRITE_TAC[CX_DEF; complex_add; RE; IM; REAL_ADD_LID]);;
408 (`!x y. Cx(x - y) = Cx(x) - Cx(y)`,
409 REWRITE_TAC[complex_sub; real_sub; CX_ADD; CX_NEG]);;
412 (`!x. Cx(inv x) = inv(Cx x)`,
413 GEN_TAC THEN REWRITE_TAC[CX_DEF; complex_inv; RE; IM; COMPLEX_EQ] THEN
414 ASM_CASES_TAC `x = &0` THEN ASM_REWRITE_TAC[] THEN
415 CONV_TAC REAL_RAT_REDUCE_CONV THEN
416 POP_ASSUM MP_TAC THEN CONV_TAC REAL_FIELD);;
419 (`!x y. Cx(x * y) = Cx(x) * Cx(y)`,
420 REWRITE_TAC[CX_DEF; complex_mul; RE; IM; REAL_MUL_LZERO; REAL_MUL_RZERO] THEN
421 REWRITE_TAC[REAL_SUB_RZERO; REAL_ADD_RID]);;
424 (`!x n. Cx(x pow n) = Cx(x) pow n`,
425 GEN_TAC THEN INDUCT_TAC THEN
426 ASM_REWRITE_TAC[complex_pow; real_pow; CX_MUL]);;
429 (`!x y. Cx(x / y) = Cx(x) / Cx(y)`,
430 REWRITE_TAC[complex_div; real_div; CX_MUL; CX_INV]);;
433 (`!x. Cx(abs x) = Cx(norm(Cx(x)))`,
434 REWRITE_TAC[CX_DEF; complex_norm; COMPLEX_EQ; RE; IM] THEN
435 REWRITE_TAC[REAL_POW_2; REAL_MUL_LZERO; REAL_ADD_RID] THEN
436 REWRITE_TAC[GSYM REAL_POW_2; POW_2_SQRT_ABS]);;
438 let COMPLEX_NORM_CX = prove
439 (`!x. norm(Cx(x)) = abs(x)`,
440 REWRITE_TAC[GSYM CX_INJ; CX_ABS]);;
442 (* ------------------------------------------------------------------------- *)
443 (* Some "linear" things hold for Re and Im too. *)
444 (* ------------------------------------------------------------------------- *)
448 REWRITE_TAC[RE; CX_DEF]);;
451 (`!x. Re(--x) = --Re(x)`,
452 REWRITE_TAC[complex_neg; RE]);;
455 (`!x y. Re(x + y) = Re(x) + Re(y)`,
456 REWRITE_TAC[complex_add; RE]);;
459 (`!x y. Re(x - y) = Re(x) - Re(y)`,
460 REWRITE_TAC[complex_sub; real_sub; RE_ADD; RE_NEG]);;
463 (`!x. Im(Cx x) = &0`,
464 REWRITE_TAC[IM; CX_DEF]);;
467 (`!x. Im(--x) = --Im(x)`,
468 REWRITE_TAC[complex_neg; IM]);;
471 (`!x y. Im(x + y) = Im(x) + Im(y)`,
472 REWRITE_TAC[complex_add; IM]);;
475 (`!x y. Im(x - y) = Im(x) - Im(y)`,
476 REWRITE_TAC[complex_sub; real_sub; IM_ADD; IM_NEG]);;
478 (* ------------------------------------------------------------------------- *)
479 (* An "expansion" theorem into the traditional notation. *)
480 (* ------------------------------------------------------------------------- *)
482 let COMPLEX_EXPAND = prove
483 (`!z. z = Cx(Re z) + ii * Cx(Im z)`,
484 REWRITE_TAC[ii] THEN SIMPLE_COMPLEX_ARITH_TAC);;
486 let COMPLEX_TRAD = prove
487 (`!x y. complex(x,y) = Cx(x) + ii * Cx(y)`,
488 REWRITE_TAC[ii] THEN SIMPLE_COMPLEX_ARITH_TAC);;
490 (* ------------------------------------------------------------------------- *)
491 (* Real and complex parts of ii and multiples. *)
492 (* ------------------------------------------------------------------------- *)
496 REWRITE_TAC[ii] THEN SIMPLE_COMPLEX_ARITH_TAC);;
500 REWRITE_TAC[ii] THEN SIMPLE_COMPLEX_ARITH_TAC);;
502 let RE_MUL_II = prove
503 (`!z. Re(z * ii) = --(Im z) /\ Re(ii * z) = --(Im z)`,
504 REWRITE_TAC[ii] THEN SIMPLE_COMPLEX_ARITH_TAC);;
506 let IM_MUL_II = prove
507 (`!z. Im(z * ii) = Re z /\ Im(ii * z) = Re z`,
508 REWRITE_TAC[ii] THEN SIMPLE_COMPLEX_ARITH_TAC);;
510 let COMPLEX_NORM_II = prove
512 REWRITE_TAC[complex_norm; RE_II; IM_II] THEN
513 CONV_TAC REAL_RAT_REDUCE_CONV THEN REWRITE_TAC[SQRT_1]);;
515 (* ------------------------------------------------------------------------- *)
516 (* Limited "multiplicative" theorems for Re and Im. *)
517 (* ------------------------------------------------------------------------- *)
520 (`!a z. Re(a % z) = a * Re z`,
521 SIMP_TAC[RE_DEF; VECTOR_MUL_COMPONENT; DIMINDEX_2; ARITH]);;
524 (`!a z. Im(a % z) = a * Im z`,
525 SIMP_TAC[IM_DEF; VECTOR_MUL_COMPONENT; DIMINDEX_2; ARITH]);;
527 let RE_MUL_CX = prove
528 (`!x z. Re(Cx(x) * z) = x * Re z /\
529 Re(z * Cx(x)) = Re z * x`,
530 SIMPLE_COMPLEX_ARITH_TAC);;
532 let IM_MUL_CX = prove
533 (`!x z. Im(Cx(x) * z) = x * Im z /\
534 Im(z * Cx(x)) = Im z * x`,
535 SIMPLE_COMPLEX_ARITH_TAC);;
537 let RE_DIV_CX = prove
538 (`!z x. Re(z / Cx(x)) = Re(z) / x`,
539 REWRITE_TAC[complex_div; real_div; GSYM CX_INV; RE_MUL_CX]);;
541 let IM_DIV_CX = prove
542 (`!z x. Im(z / Cx(x)) = Im(z) / x`,
543 REWRITE_TAC[complex_div; real_div; GSYM CX_INV; IM_MUL_CX]);;
545 (* ------------------------------------------------------------------------- *)
546 (* Syntax constructors etc. for complex constants. *)
547 (* ------------------------------------------------------------------------- *)
549 let is_complex_const =
553 let l,r = dest_comb tm in l = cx_tm & is_ratconst r;;
555 let dest_complex_const =
558 let l,r = dest_comb tm in
559 if l = cx_tm then rat_of_term r
560 else failwith "dest_complex_const";;
562 let mk_complex_const =
565 mk_comb(cx_tm,term_of_rat r);;
567 (* ------------------------------------------------------------------------- *)
568 (* Conversions for arithmetic on complex constants. *)
569 (* ------------------------------------------------------------------------- *)
571 let COMPLEX_RAT_EQ_CONV =
572 GEN_REWRITE_CONV I [CX_INJ] THENC REAL_RAT_EQ_CONV;;
574 let COMPLEX_RAT_MUL_CONV =
575 GEN_REWRITE_CONV I [GSYM CX_MUL] THENC RAND_CONV REAL_RAT_MUL_CONV;;
577 let COMPLEX_RAT_ADD_CONV =
578 GEN_REWRITE_CONV I [GSYM CX_ADD] THENC RAND_CONV REAL_RAT_ADD_CONV;;
580 let COMPLEX_RAT_POW_CONV =
582 and n_tm = `n:num` in
583 let pth = SYM(SPECL [x_tm; n_tm] CX_POW) in
585 let lop,r = dest_comb tm in
586 let op,bod = dest_comb lop in
587 let th1 = INST [rand bod,x_tm; r,n_tm] pth in
588 let tm1,tm2 = dest_comb(concl th1) in
589 if rand tm1 <> tm then failwith "COMPLEX_RAT_POW_CONV" else
590 let tm3,tm4 = dest_comb tm2 in
591 TRANS th1 (AP_TERM tm3 (REAL_RAT_REDUCE_CONV tm4));;
593 (* ------------------------------------------------------------------------- *)
594 (* Complex polynomial normalizer. *)
595 (* ------------------------------------------------------------------------- *)
597 let COMPLEX_POLY_CLAUSES = prove
598 (`(!x y z. x + (y + z) = (x + y) + z) /\
599 (!x y. x + y = y + x) /\
600 (!x. Cx(&0) + x = x) /\
601 (!x y z. x * (y * z) = (x * y) * z) /\
602 (!x y. x * y = y * x) /\
603 (!x. Cx(&1) * x = x) /\
604 (!x. Cx(&0) * x = Cx(&0)) /\
605 (!x y z. x * (y + z) = x * y + x * z) /\
606 (!x. x pow 0 = Cx(&1)) /\
607 (!x n. x pow (SUC n) = x * x pow n)`,
608 REWRITE_TAC[complex_pow] THEN SIMPLE_COMPLEX_ARITH_TAC)
609 and COMPLEX_POLY_NEG_CLAUSES = prove
610 (`(!x. --x = Cx(-- &1) * x) /\
611 (!x y. x - y = x + Cx(-- &1) * y)`,
612 SIMPLE_COMPLEX_ARITH_TAC);;
614 let COMPLEX_POLY_NEG_CONV,COMPLEX_POLY_ADD_CONV,COMPLEX_POLY_SUB_CONV,
615 COMPLEX_POLY_MUL_CONV,COMPLEX_POLY_POW_CONV,COMPLEX_POLY_CONV =
616 SEMIRING_NORMALIZERS_CONV COMPLEX_POLY_CLAUSES COMPLEX_POLY_NEG_CLAUSES
618 COMPLEX_RAT_ADD_CONV,COMPLEX_RAT_MUL_CONV,COMPLEX_RAT_POW_CONV)
621 (* ------------------------------------------------------------------------- *)
622 (* Extend it to handle "inv" and division, by constants after normalization. *)
623 (* ------------------------------------------------------------------------- *)
625 let COMPLEX_RAT_INV_CONV =
626 REWR_CONV(GSYM CX_INV) THENC RAND_CONV REAL_RAT_INV_CONV;;
628 let COMPLEX_POLY_CONV =
629 let neg_tm = `(--):complex->complex`
630 and inv_tm = `inv:complex->complex`
631 and add_tm = `(+):complex->complex->complex`
632 and sub_tm = `(-):complex->complex->complex`
633 and mul_tm = `(*):complex->complex->complex`
634 and div_tm = `(/):complex->complex->complex`
635 and pow_tm = `(pow):complex->num->complex`
636 and div_conv = REWR_CONV complex_div in
637 let rec COMPLEX_POLY_CONV tm =
638 if not(is_comb tm) or is_ratconst tm then REFL tm else
639 let lop,r = dest_comb tm in
641 let th1 = AP_TERM lop (COMPLEX_POLY_CONV r) in
642 TRANS th1 (COMPLEX_POLY_NEG_CONV (rand(concl th1)))
643 else if lop = inv_tm then
644 let th1 = AP_TERM lop (COMPLEX_POLY_CONV r) in
645 TRANS th1 (TRY_CONV COMPLEX_RAT_INV_CONV (rand(concl th1)))
646 else if not(is_comb lop) then REFL tm else
647 let op,l = dest_comb lop in
649 let th1 = AP_THM (AP_TERM op (COMPLEX_POLY_CONV l)) r in
650 TRANS th1 (TRY_CONV COMPLEX_POLY_POW_CONV (rand(concl th1)))
651 else if op = add_tm or op = mul_tm or op = sub_tm then
652 let th1 = MK_COMB(AP_TERM op (COMPLEX_POLY_CONV l),
653 COMPLEX_POLY_CONV r) in
654 let fn = if op = add_tm then COMPLEX_POLY_ADD_CONV
655 else if op = mul_tm then COMPLEX_POLY_MUL_CONV
656 else COMPLEX_POLY_SUB_CONV in
657 TRANS th1 (fn (rand(concl th1)))
658 else if op = div_tm then
659 let th1 = div_conv tm in
660 TRANS th1 (COMPLEX_POLY_CONV (rand(concl th1)))
664 (* ------------------------------------------------------------------------- *)
665 (* Complex number version of usual ring procedure. *)
666 (* ------------------------------------------------------------------------- *)
668 let COMPLEX_RING,complex_ideal_cofactors =
669 let COMPLEX_INTEGRAL = prove
670 (`(!x. Cx(&0) * x = Cx(&0)) /\
671 (!x y z. (x + y = x + z) <=> (y = z)) /\
672 (!w x y z. (w * y + x * z = w * z + x * y) <=> (w = x) \/ (y = z))`,
673 REWRITE_TAC[COMPLEX_ENTIRE; SIMPLE_COMPLEX_ARITH
674 `(w * y + x * z = w * z + x * y) <=>
675 (w - x) * (y - z) = Cx(&0)`] THEN
676 SIMPLE_COMPLEX_ARITH_TAC)
677 and COMPLEX_RABINOWITSCH = prove
678 (`!x y:complex. ~(x = y) <=> ?z. (x - y) * z = Cx(&1)`,
680 GEN_REWRITE_TAC (LAND_CONV o RAND_CONV) [GSYM COMPLEX_SUB_0] THEN
681 MESON_TAC[COMPLEX_MUL_RINV; COMPLEX_MUL_LZERO;
682 SIMPLE_COMPLEX_ARITH `~(Cx(&1) = Cx(&0))`])
683 and COMPLEX_IIII = prove
684 (`ii * ii + Cx(&1) = Cx(&0)`,
685 REWRITE_TAC[ii; CX_DEF; complex_mul; complex_add; RE; IM] THEN
686 AP_TERM_TAC THEN BINOP_TAC THEN REAL_ARITH_TAC) in
689 (dest_complex_const,mk_complex_const,COMPLEX_RAT_EQ_CONV,
690 `(--):complex->complex`,`(+):complex->complex->complex`,
691 `(-):complex->complex->complex`,`(inv):complex->complex`,
692 `(*):complex->complex->complex`,`(/):complex->complex->complex`,
693 `(pow):complex->num->complex`,
694 COMPLEX_INTEGRAL,COMPLEX_RABINOWITSCH,COMPLEX_POLY_CONV)
695 and ii_tm = `ii` and iiii_tm = concl COMPLEX_IIII in
696 (fun tm -> if free_in ii_tm tm then
697 MP (ring (mk_imp(iiii_tm,tm))) COMPLEX_IIII
701 (* ------------------------------------------------------------------------- *)
702 (* Most basic properties of inverses. *)
703 (* ------------------------------------------------------------------------- *)
705 let COMPLEX_INV_0 = prove
706 (`inv(Cx(&0)) = Cx(&0)`,
707 SIMPLE_COMPLEX_ARITH_TAC);;
709 let COMPLEX_INV_1 = prove
710 (`inv(Cx(&1)) = Cx(&1)`,
711 SIMPLE_COMPLEX_ARITH_TAC);;
713 let COMPLEX_INV_MUL = prove
714 (`!w z. inv(w * z) = inv(w) * inv(z)`,
716 MAP_EVERY ASM_CASES_TAC [`w = Cx(&0)`; `z = Cx(&0)`] THEN
717 ASM_REWRITE_TAC[COMPLEX_INV_0; COMPLEX_MUL_LZERO; COMPLEX_MUL_RZERO] THEN
718 REPEAT(POP_ASSUM MP_TAC) THEN
719 REWRITE_TAC[complex_mul; complex_inv; RE; IM; COMPLEX_EQ; CX_DEF] THEN
720 REWRITE_TAC[GSYM REAL_SOS_EQ_0] THEN CONV_TAC REAL_FIELD);;
722 let COMPLEX_POW_INV = prove
723 (`!x n. (inv x) pow n = inv(x pow n)`,
724 GEN_TAC THEN INDUCT_TAC THEN
725 ASM_REWRITE_TAC[complex_pow; COMPLEX_INV_1; COMPLEX_INV_MUL]);;
727 let COMPLEX_INV_INV = prove
728 (`!x:complex. inv(inv x) = x`,
729 GEN_TAC THEN ASM_CASES_TAC `x = Cx(&0)` THEN
730 ASM_REWRITE_TAC[COMPLEX_INV_0] THEN
731 POP_ASSUM MP_TAC THEN
732 MAP_EVERY (fun t -> MP_TAC(SPEC t COMPLEX_MUL_RINV))
733 [`x:complex`; `inv(x):complex`] THEN
734 CONV_TAC COMPLEX_RING);;
736 let COMPLEX_INV_DIV = prove
737 (`!w z:complex. inv(w / z) = z / w`,
738 REWRITE_TAC[complex_div; COMPLEX_INV_MUL; COMPLEX_INV_INV] THEN
739 REWRITE_TAC[COMPLEX_MUL_AC]);;
741 (* ------------------------------------------------------------------------- *)
742 (* And also field procedure. *)
743 (* ------------------------------------------------------------------------- *)
745 let COMPLEX_EQ_MUL_LCANCEL = prove
746 (`!x y z. (x * y = x * z) <=> (x = Cx(&0)) \/ (y = z)`,
747 CONV_TAC COMPLEX_RING);;
749 let COMPLEX_EQ_MUL_RCANCEL = prove
750 (`!x y z. (x * z = y * z) <=> (x = y) \/ (z = Cx(&0))`,
751 CONV_TAC COMPLEX_RING);;
755 TOP_DEPTH_CONV BETA_CONV THENC
756 PURE_REWRITE_CONV[FORALL_SIMP; EXISTS_SIMP; complex_div;
757 COMPLEX_INV_INV; COMPLEX_INV_MUL; GSYM COMPLEX_POW_INV] THENC
758 NNFC_CONV THENC DEPTH_BINOP_CONV `(/\)` CONDS_CELIM_CONV THENC
760 and setup_conv = NNF_CONV THENC WEAK_CNF_CONV THENC CONJ_CANON_CONV
762 let inv_tm = `inv:complex->complex`
763 and is_div = is_binop `(/):complex->complex->complex` in
764 fun tm -> (is_div tm or (is_comb tm & rator tm = inv_tm)) &
765 not(is_ratconst(rand tm)) in
766 let BASIC_COMPLEX_FIELD tm =
767 let is_freeinv t = is_inv t & free_in t tm in
768 let itms = setify(map rand (find_terms is_freeinv tm)) in
769 let hyps = map (fun t -> SPEC t COMPLEX_MUL_RINV) itms in
770 let tm' = itlist (fun th t -> mk_imp(concl th,t)) hyps tm in
771 let th1 = setup_conv tm' in
772 let cjs = conjuncts(rand(concl th1)) in
773 let ths = map COMPLEX_RING cjs in
774 let th2 = EQ_MP (SYM th1) (end_itlist CONJ ths) in
775 rev_itlist (C MP) hyps th2 in
777 let th0 = prenex_conv tm in
778 let tm0 = rand(concl th0) in
779 let avs,bod = strip_forall tm0 in
780 let th1 = setup_conv bod in
781 let ths = map BASIC_COMPLEX_FIELD (conjuncts(rand(concl th1))) in
782 EQ_MP (SYM th0) (GENL avs (EQ_MP (SYM th1) (end_itlist CONJ ths)));;
784 (* ------------------------------------------------------------------------- *)
785 (* More trivial lemmas. *)
786 (* ------------------------------------------------------------------------- *)
788 let COMPLEX_DIV_1 = prove
789 (`!z. z / Cx(&1) = z`,
790 CONV_TAC COMPLEX_FIELD);;
792 let COMPLEX_DIV_LMUL = prove
793 (`!x y. ~(y = Cx(&0)) ==> y * x / y = x`,
794 CONV_TAC COMPLEX_FIELD);;
796 let COMPLEX_DIV_RMUL = prove
797 (`!x y. ~(y = Cx(&0)) ==> x / y * y = x`,
798 CONV_TAC COMPLEX_FIELD);;
800 let COMPLEX_INV_EQ_0 = prove
801 (`!x. inv x = Cx(&0) <=> x = Cx(&0)`,
802 GEN_TAC THEN ASM_CASES_TAC `x = Cx(&0)` THEN
803 ASM_REWRITE_TAC[COMPLEX_INV_0] THEN POP_ASSUM MP_TAC THEN
804 CONV_TAC COMPLEX_FIELD);;
806 let COMPLEX_INV_NEG = prove
807 (`!x:complex. inv(--x) = --(inv x)`,
808 GEN_TAC THEN ASM_CASES_TAC `x = Cx(&0)` THEN
809 ASM_REWRITE_TAC[COMPLEX_INV_0; COMPLEX_NEG_0] THEN
810 POP_ASSUM MP_TAC THEN CONV_TAC COMPLEX_FIELD);;
812 let COMPLEX_NEG_INV = prove
813 (`!x:complex. --(inv x) = inv(--x)`,
814 REWRITE_TAC[COMPLEX_INV_NEG]);;
816 let COMPLEX_INV_EQ_1 = prove
817 (`!x. inv x = Cx(&1) <=> x = Cx(&1)`,
818 GEN_TAC THEN ASM_CASES_TAC `x = Cx(&0)` THEN
819 ASM_REWRITE_TAC[COMPLEX_INV_0] THEN POP_ASSUM MP_TAC THEN
820 CONV_TAC COMPLEX_FIELD);;
822 let COMPLEX_DIV_EQ_0 = prove
823 (`!w z. w / z = Cx(&0) <=> w = Cx(&0) \/ z = Cx(&0)`,
824 REWRITE_TAC[complex_div; COMPLEX_INV_EQ_0; COMPLEX_ENTIRE]);;
826 (* ------------------------------------------------------------------------- *)
828 (* ------------------------------------------------------------------------- *)
830 let COMPLEX_POW_ADD = prove
831 (`!x m n. x pow (m + n) = x pow m * x pow n`,
832 GEN_TAC THEN INDUCT_TAC THEN
833 ASM_REWRITE_TAC[ADD_CLAUSES; complex_pow;
834 COMPLEX_MUL_LID; COMPLEX_MUL_ASSOC]);;
836 let COMPLEX_POW_POW = prove
837 (`!x m n. (x pow m) pow n = x pow (m * n)`,
838 GEN_TAC THEN GEN_TAC THEN INDUCT_TAC THEN
839 ASM_REWRITE_TAC[complex_pow; MULT_CLAUSES; COMPLEX_POW_ADD]);;
841 let COMPLEX_POW_1 = prove
843 REWRITE_TAC[num_CONV `1`] THEN REWRITE_TAC[complex_pow; COMPLEX_MUL_RID]);;
845 let COMPLEX_POW_2 = prove
846 (`!x. x pow 2 = x * x`,
847 REWRITE_TAC[num_CONV `2`] THEN REWRITE_TAC[complex_pow; COMPLEX_POW_1]);;
849 let COMPLEX_POW_NEG = prove
850 (`!x n. (--x) pow n = if EVEN n then x pow n else --(x pow n)`,
851 GEN_TAC THEN INDUCT_TAC THEN
852 ASM_REWRITE_TAC[complex_pow; EVEN] THEN
853 ASM_CASES_TAC `EVEN n` THEN
854 ASM_REWRITE_TAC[COMPLEX_MUL_RNEG; COMPLEX_MUL_LNEG; COMPLEX_NEG_NEG]);;
856 let COMPLEX_POW_ONE = prove
857 (`!n. Cx(&1) pow n = Cx(&1)`,
858 INDUCT_TAC THEN ASM_REWRITE_TAC[complex_pow; COMPLEX_MUL_LID]);;
860 let COMPLEX_POW_MUL = prove
861 (`!x y n. (x * y) pow n = (x pow n) * (y pow n)`,
862 GEN_TAC THEN GEN_TAC THEN INDUCT_TAC THEN
863 ASM_REWRITE_TAC[complex_pow; COMPLEX_MUL_LID; COMPLEX_MUL_AC]);;
865 let COMPLEX_POW_DIV = prove
866 (`!x y n. (x / y) pow n = (x pow n) / (y pow n)`,
867 REWRITE_TAC[complex_div; COMPLEX_POW_MUL; COMPLEX_POW_INV]);;
869 let COMPLEX_POW_II_2 = prove
870 (`ii pow 2 = --Cx(&1)`,
871 REWRITE_TAC[ii; COMPLEX_POW_2; complex_mul; CX_DEF; RE; IM; complex_neg] THEN
872 CONV_TAC REAL_RAT_REDUCE_CONV);;
874 let COMPLEX_POW_EQ_0 = prove
875 (`!x n. (x pow n = Cx(&0)) <=> (x = Cx(&0)) /\ ~(n = 0)`,
876 GEN_TAC THEN INDUCT_TAC THEN
877 ASM_REWRITE_TAC[NOT_SUC; complex_pow; COMPLEX_ENTIRE] THENL
878 [SIMPLE_COMPLEX_ARITH_TAC; CONV_TAC TAUT]);;
880 let COMPLEX_POW_ZERO = prove
881 (`!n. Cx(&0) pow n = if n = 0 then Cx(&1) else Cx(&0)`,
882 INDUCT_TAC THEN REWRITE_TAC[complex_pow; COMPLEX_MUL_LZERO; NOT_SUC]);;
884 let COMPLEX_INV_II = prove
886 CONV_TAC COMPLEX_FIELD);;
888 let COMPLEX_DIV_POW = prove
889 (`!x:complex n k:num.
890 ~(x= Cx(&0)) /\ k <= n /\ ~(k = 0)
891 ==> x pow (n-k) = x pow n / x pow k`,
892 REPEAT STRIP_TAC THEN SUBGOAL_THEN `x:complex pow (n - k) * x pow k =
893 x pow n / x pow k * x pow k` (fun th-> ASM_MESON_TAC
894 [th;COMPLEX_POW_EQ_0;COMPLEX_EQ_MUL_RCANCEL])
895 THEN ASM_SIMP_TAC[GSYM COMPLEX_POW_ADD;SUB_ADD] THEN
896 MP_TAC (MESON [COMPLEX_POW_EQ_0;ASSUME `~(k = 0)`; ASSUME `~(x = Cx(&0))`]
897 `~(x pow k = Cx(&0))`) THEN ASM_SIMP_TAC[COMPLEX_DIV_RMUL]);;
899 (* ------------------------------------------------------------------------- *)
900 (* Norms (aka "moduli"). *)
901 (* ------------------------------------------------------------------------- *)
903 let COMPLEX_VEC_0 = prove
905 SIMP_TAC[CART_EQ; VEC_COMPONENT; CX_DEF; complex;
906 DIMINDEX_2; FORALL_2; VECTOR_2]);;
908 let COMPLEX_NORM_ZERO = prove
909 (`!z. (norm z = &0) <=> (z = Cx(&0))`,
910 REWRITE_TAC[NORM_EQ_0; COMPLEX_VEC_0]);;
912 let COMPLEX_NORM_NUM = prove
913 (`!n. norm(Cx(&n)) = &n`,
914 REWRITE_TAC[COMPLEX_NORM_CX; REAL_ABS_NUM]);;
916 let COMPLEX_NORM_0 = prove
917 (`norm(Cx(&0)) = &0`,
918 MESON_TAC[COMPLEX_NORM_ZERO]);;
920 let COMPLEX_NORM_NZ = prove
921 (`!z. &0 < norm(z) <=> ~(z = Cx(&0))`,
922 REWRITE_TAC[NORM_POS_LT; COMPLEX_VEC_0]);;
924 let COMPLEX_NORM_MUL = prove
925 (`!w z. norm(w * z) = norm(w) * norm(z)`,
926 REPEAT GEN_TAC THEN REWRITE_TAC[complex_norm; complex_mul; RE; IM] THEN
927 SIMP_TAC[GSYM SQRT_MUL; REAL_POW_2; REAL_LE_ADD; REAL_LE_SQUARE] THEN
928 AP_TERM_TAC THEN REAL_ARITH_TAC);;
930 let COMPLEX_NORM_POW = prove
931 (`!z n. norm(z pow n) = norm(z) pow n`,
932 GEN_TAC THEN INDUCT_TAC THEN
933 ASM_REWRITE_TAC[complex_pow; real_pow; COMPLEX_NORM_NUM; COMPLEX_NORM_MUL]);;
935 let COMPLEX_NORM_INV = prove
936 (`!z. norm(inv z) = inv(norm z)`,
937 GEN_TAC THEN REWRITE_TAC[complex_norm; complex_inv; RE; IM] THEN
938 REWRITE_TAC[REAL_POW_2; real_div] THEN
939 REWRITE_TAC[REAL_ARITH `(r * d) * r * d + (--i * d) * --i * d =
940 (r * r + i * i) * d * d:real`] THEN
941 ASM_CASES_TAC `Re z * Re z + Im z * Im z = &0` THENL
942 [ASM_REWRITE_TAC[REAL_INV_0; SQRT_0; REAL_MUL_LZERO]; ALL_TAC] THEN
943 CONV_TAC SYM_CONV THEN MATCH_MP_TAC REAL_MUL_RINV_UNIQ THEN
944 SIMP_TAC[GSYM SQRT_MUL; REAL_LE_MUL; REAL_LE_INV_EQ; REAL_LE_ADD;
946 ONCE_REWRITE_TAC[AC REAL_MUL_AC
947 `a * a * b * b:real = (a * b) * (a * b)`] THEN
948 ASM_SIMP_TAC[REAL_MUL_RINV; REAL_MUL_LID; SQRT_1]);;
950 let COMPLEX_NORM_DIV = prove
951 (`!w z. norm(w / z) = norm(w) / norm(z)`,
952 REWRITE_TAC[complex_div; real_div; COMPLEX_NORM_INV; COMPLEX_NORM_MUL]);;
954 let COMPLEX_NORM_TRIANGLE_SUB = prove
955 (`!w z. norm(w) <= norm(w + z) + norm(z)`,
956 MESON_TAC[NORM_TRIANGLE; NORM_NEG; COMPLEX_ADD_ASSOC;
957 COMPLEX_ADD_RINV; COMPLEX_ADD_RID]);;
959 let COMPLEX_NORM_ABS_NORM = prove
960 (`!w z. abs(norm w - norm z) <= norm(w - z)`,
962 MATCH_MP_TAC(REAL_ARITH
963 `a - b <= x /\ b - a <= x ==> abs(a - b) <= x:real`) THEN
964 MESON_TAC[COMPLEX_NEG_SUB; NORM_NEG; REAL_LE_SUB_RADD; complex_sub;
965 COMPLEX_NORM_TRIANGLE_SUB]);;
967 let COMPLEX_POW_EQ_1 = prove
968 (`!z n. z pow n = Cx(&1) ==> norm(z) = &1 \/ n = 0`,
970 DISCH_THEN(MP_TAC o AP_TERM `norm:complex->real`) THEN
971 SIMP_TAC[COMPLEX_NORM_POW; COMPLEX_NORM_CX; REAL_POW_EQ_1; REAL_ABS_NUM] THEN
972 SIMP_TAC[REAL_ABS_NORM] THEN CONV_TAC TAUT);;
974 (* ------------------------------------------------------------------------- *)
975 (* Complex conjugate. *)
976 (* ------------------------------------------------------------------------- *)
978 let cnj = new_definition
979 `cnj(z) = complex(Re(z),--(Im(z)))`;;
981 (* ------------------------------------------------------------------------- *)
982 (* Conjugation is an automorphism. *)
983 (* ------------------------------------------------------------------------- *)
986 (`!w z. (cnj(w) = cnj(z)) <=> (w = z)`,
987 REWRITE_TAC[cnj; COMPLEX_EQ; RE; IM; REAL_EQ_NEG2]);;
990 (`!z. cnj(cnj z) = z`,
991 REWRITE_TAC[cnj; COMPLEX_EQ; RE; IM; REAL_NEG_NEG]);;
994 (`!x. cnj(Cx x) = Cx x`,
995 REWRITE_TAC[cnj; COMPLEX_EQ; CX_DEF; REAL_NEG_0; RE; IM]);;
997 let COMPLEX_NORM_CNJ = prove
998 (`!z. norm(cnj z) = norm(z)`,
999 REWRITE_TAC[complex_norm; cnj; REAL_POW_2] THEN
1000 REWRITE_TAC[REAL_MUL_LNEG; REAL_MUL_RNEG; RE; IM; REAL_NEG_NEG]);;
1003 (`!z. cnj(--z) = --(cnj z)`,
1004 REWRITE_TAC[cnj; complex_neg; COMPLEX_EQ; RE; IM]);;
1007 (`!z. cnj(inv z) = inv(cnj z)`,
1008 REWRITE_TAC[cnj; complex_inv; COMPLEX_EQ; RE; IM] THEN
1009 REWRITE_TAC[real_div; REAL_NEG_NEG; REAL_POW_2;
1010 REAL_MUL_LNEG; REAL_MUL_RNEG]);;
1013 (`!w z. cnj(w + z) = cnj(w) + cnj(z)`,
1014 REWRITE_TAC[cnj; complex_add; COMPLEX_EQ; RE; IM] THEN
1015 REWRITE_TAC[REAL_NEG_ADD; REAL_MUL_LNEG; REAL_MUL_RNEG; REAL_NEG_NEG]);;
1018 (`!w z. cnj(w - z) = cnj(w) - cnj(z)`,
1019 REWRITE_TAC[complex_sub; CNJ_ADD; CNJ_NEG]);;
1022 (`!w z. cnj(w * z) = cnj(w) * cnj(z)`,
1023 REWRITE_TAC[cnj; complex_mul; COMPLEX_EQ; RE; IM] THEN
1024 REWRITE_TAC[REAL_NEG_ADD; REAL_MUL_LNEG; REAL_MUL_RNEG; REAL_NEG_NEG]);;
1027 (`!w z. cnj(w / z) = cnj(w) / cnj(z)`,
1028 REWRITE_TAC[complex_div; CNJ_MUL; CNJ_INV]);;
1031 (`!z n. cnj(z pow n) = cnj(z) pow n`,
1032 GEN_TAC THEN INDUCT_TAC THEN
1033 ASM_REWRITE_TAC[complex_pow; CNJ_MUL; CNJ_CX]);;
1036 (`!z. Re(cnj z) = Re z`,
1037 REWRITE_TAC[cnj; RE]);;
1040 (`!z. Im(cnj z) = --Im z`,
1041 REWRITE_TAC[cnj; IM]);;
1043 let CNJ_EQ_CX = prove
1044 (`!x z. cnj z = Cx x <=> z = Cx x`,
1045 REWRITE_TAC[COMPLEX_EQ; RE_CNJ; IM_CNJ; RE_CX; IM_CX] THEN
1046 CONV_TAC REAL_RING);;
1048 let CNJ_EQ_0 = prove
1049 (`!z. cnj z = Cx(&0) <=> z = Cx(&0)`,
1050 REWRITE_TAC[CNJ_EQ_CX]);;
1052 let COMPLEX_ADD_CNJ = prove
1053 (`(!z. z + cnj z = Cx(&2 * Re z)) /\ (!z. cnj z + z = Cx(&2 * Re z))`,
1054 REWRITE_TAC[COMPLEX_EQ; RE_CX; IM_CX; RE_ADD; IM_ADD; RE_CNJ; IM_CNJ] THEN
1059 REWRITE_TAC[cnj; ii; RE; IM; complex_neg; REAL_NEG_0]);;
1061 let CX_RE_CNJ = prove
1062 (`!z. Cx(Re z) = (z + cnj z) / Cx(&2)`,
1063 REWRITE_TAC[COMPLEX_EQ; RE_DIV_CX; IM_DIV_CX; RE_CX; IM_CX] THEN
1064 REWRITE_TAC[RE_ADD; IM_ADD; RE_CNJ; IM_CNJ] THEN REAL_ARITH_TAC);;
1066 let CX_IM_CNJ = prove
1067 (`!z. Cx(Im z) = --ii * (z - cnj z) / Cx(&2)`,
1068 REWRITE_TAC[COMPLEX_EQ; RE_DIV_CX; IM_DIV_CX; RE_CX; IM_CX;
1069 COMPLEX_MUL_LNEG; RE_NEG; IM_NEG; RE_MUL_II; IM_MUL_II] THEN
1070 REWRITE_TAC[RE_SUB; IM_SUB; RE_CNJ; IM_CNJ] THEN REAL_ARITH_TAC);;
1072 let FORALL_CNJ = prove
1073 (`(!z. P(cnj z)) <=> (!z. P z)`,
1074 MESON_TAC[CNJ_CNJ]);;
1076 let EXISTS_CNJ = prove
1077 (`(?z. P(cnj z)) <=> (?z. P z)`,
1078 MESON_TAC[CNJ_CNJ]);;
1080 (* ------------------------------------------------------------------------- *)
1081 (* Slightly ad hoc theorems relating multiplication, inverse and conjugation *)
1082 (* ------------------------------------------------------------------------- *)
1084 let COMPLEX_NORM_POW_2 = prove
1085 (`!z. Cx(norm z) pow 2 = z * cnj z`,
1086 GEN_TAC THEN REWRITE_TAC [GSYM CX_POW; COMPLEX_SQNORM] THEN
1087 REWRITE_TAC [cnj; complex_mul; CX_DEF; RE; IM; COMPLEX_EQ] THEN
1088 CONV_TAC REAL_RING);;
1090 let COMPLEX_MUL_CNJ = prove
1091 (`!z. cnj z * z = Cx(norm(z)) pow 2 /\ z * cnj z = Cx(norm(z)) pow 2`,
1092 GEN_TAC THEN REWRITE_TAC[COMPLEX_MUL_SYM] THEN
1093 REWRITE_TAC[cnj; complex_mul; RE; IM; GSYM CX_POW; COMPLEX_SQNORM] THEN
1094 REWRITE_TAC[CX_DEF] THEN AP_TERM_TAC THEN BINOP_TAC THEN
1095 CONV_TAC REAL_RING);;
1097 let COMPLEX_INV_CNJ = prove
1098 (`!z. inv z = cnj z / Cx(norm z) pow 2`,
1099 GEN_TAC THEN ASM_CASES_TAC `z = Cx(&0)` THENL
1100 [ASM_REWRITE_TAC[CNJ_CX; complex_div; COMPLEX_INV_0; COMPLEX_MUL_LZERO];
1101 MATCH_MP_TAC(COMPLEX_FIELD
1102 `x * y = z /\ ~(x = Cx(&0)) /\ ~(z = Cx(&0)) ==> inv x = y / z`) THEN
1103 ASM_REWRITE_TAC[COMPLEX_MUL_CNJ; GSYM CX_POW; CX_INJ; REAL_POW_EQ_0] THEN
1104 ASM_REWRITE_TAC[COMPLEX_NORM_ZERO; ARITH]]);;
1106 let COMPLEX_DIV_CNJ = prove
1107 (`!a b. a / b = (a * cnj b) / Cx(norm b) pow 2`,
1108 REPEAT GEN_TAC THEN REWRITE_TAC[complex_div; GSYM COMPLEX_MUL_ASSOC] THEN
1109 AP_TERM_TAC THEN GEN_REWRITE_TAC LAND_CONV [COMPLEX_INV_CNJ] THEN
1110 REWRITE_TAC[complex_div]);;
1112 let RE_COMPLEX_DIV_EQ_0 = prove
1113 (`!a b. Re(a / b) = &0 <=> Re(a * cnj b) = &0`,
1114 REPEAT GEN_TAC THEN ONCE_REWRITE_TAC[COMPLEX_DIV_CNJ] THEN
1115 REWRITE_TAC[complex_div; GSYM CX_POW; GSYM CX_INV] THEN
1116 REWRITE_TAC[RE_MUL_CX; REAL_INV_EQ_0; REAL_POW_EQ_0; ARITH;
1117 REAL_ENTIRE; COMPLEX_NORM_ZERO] THEN
1118 ASM_CASES_TAC `b = Cx(&0)` THEN ASM_REWRITE_TAC[] THEN
1119 REWRITE_TAC[CNJ_CX; COMPLEX_MUL_RZERO; RE_CX]);;
1121 let IM_COMPLEX_DIV_EQ_0 = prove
1122 (`!a b. Im(a / b) = &0 <=> Im(a * cnj b) = &0`,
1123 REPEAT GEN_TAC THEN ONCE_REWRITE_TAC[COMPLEX_DIV_CNJ] THEN
1124 REWRITE_TAC[complex_div; GSYM CX_POW; GSYM CX_INV] THEN
1125 REWRITE_TAC[IM_MUL_CX; REAL_INV_EQ_0; REAL_POW_EQ_0; ARITH;
1126 REAL_ENTIRE; COMPLEX_NORM_ZERO] THEN
1127 ASM_CASES_TAC `b = Cx(&0)` THEN ASM_REWRITE_TAC[] THEN
1128 REWRITE_TAC[CNJ_CX; COMPLEX_MUL_RZERO; IM_CX]);;
1130 let RE_COMPLEX_DIV_GT_0 = prove
1131 (`!a b. &0 < Re(a / b) <=> &0 < Re(a * cnj b)`,
1132 REPEAT GEN_TAC THEN ONCE_REWRITE_TAC[COMPLEX_DIV_CNJ] THEN
1133 REWRITE_TAC[complex_div; GSYM CX_POW; GSYM CX_INV] THEN
1134 REWRITE_TAC[RE_MUL_CX; REAL_INV_EQ_0; REAL_POW_EQ_0; ARITH;
1135 REAL_ENTIRE; COMPLEX_NORM_ZERO] THEN
1136 ASM_CASES_TAC `b = Cx(&0)` THEN
1137 ASM_REWRITE_TAC[CNJ_CX; COMPLEX_MUL_RZERO; RE_CX; REAL_MUL_LZERO] THEN
1138 REWRITE_TAC[REAL_ARITH `&0 < a * x <=> &0 * x < a * x`] THEN
1139 ASM_SIMP_TAC[REAL_LT_RMUL_EQ; REAL_LT_INV_EQ; REAL_POW_LT; ARITH;
1142 let IM_COMPLEX_DIV_GT_0 = prove
1143 (`!a b. &0 < Im(a / b) <=> &0 < Im(a * cnj b)`,
1144 REPEAT GEN_TAC THEN ONCE_REWRITE_TAC[COMPLEX_DIV_CNJ] THEN
1145 REWRITE_TAC[complex_div; GSYM CX_POW; GSYM CX_INV] THEN
1146 REWRITE_TAC[IM_MUL_CX; REAL_INV_EQ_0; REAL_POW_EQ_0; ARITH;
1147 REAL_ENTIRE; COMPLEX_NORM_ZERO] THEN
1148 ASM_CASES_TAC `b = Cx(&0)` THEN
1149 ASM_REWRITE_TAC[CNJ_CX; COMPLEX_MUL_RZERO; IM_CX; REAL_MUL_LZERO] THEN
1150 REWRITE_TAC[REAL_ARITH `&0 < a * x <=> &0 * x < a * x`] THEN
1151 ASM_SIMP_TAC[REAL_LT_RMUL_EQ; REAL_LT_INV_EQ; REAL_POW_LT; ARITH;
1154 let RE_COMPLEX_DIV_GE_0 = prove
1155 (`!a b. &0 <= Re(a / b) <=> &0 <= Re(a * cnj b)`,
1156 REWRITE_TAC[REAL_ARITH `&0 <= x <=> &0 < x \/ x = &0`] THEN
1157 REWRITE_TAC[RE_COMPLEX_DIV_GT_0; RE_COMPLEX_DIV_EQ_0]);;
1159 let IM_COMPLEX_DIV_GE_0 = prove
1160 (`!a b. &0 <= Im(a / b) <=> &0 <= Im(a * cnj b)`,
1161 REWRITE_TAC[REAL_ARITH `&0 <= x <=> &0 < x \/ x = &0`] THEN
1162 REWRITE_TAC[IM_COMPLEX_DIV_GT_0; IM_COMPLEX_DIV_EQ_0]);;
1164 let RE_COMPLEX_DIV_LE_0 = prove
1165 (`!a b. Re(a / b) <= &0 <=> Re(a * cnj b) <= &0`,
1166 REWRITE_TAC[GSYM REAL_NOT_LT; RE_COMPLEX_DIV_GT_0]);;
1168 let IM_COMPLEX_DIV_LE_0 = prove
1169 (`!a b. Im(a / b) <= &0 <=> Im(a * cnj b) <= &0`,
1170 REWRITE_TAC[GSYM REAL_NOT_LT; IM_COMPLEX_DIV_GT_0]);;
1172 let RE_COMPLEX_DIV_LT_0 = prove
1173 (`!a b. Re(a / b) < &0 <=> Re(a * cnj b) < &0`,
1174 REWRITE_TAC[GSYM REAL_NOT_LE; RE_COMPLEX_DIV_GE_0]);;
1176 let IM_COMPLEX_DIV_LT_0 = prove
1177 (`!a b. Im(a / b) < &0 <=> Im(a * cnj b) < &0`,
1178 REWRITE_TAC[GSYM REAL_NOT_LE; IM_COMPLEX_DIV_GE_0]);;
1180 let IM_COMPLEX_INV_GE_0 = prove
1181 (`!z. &0 <= Im(inv z) <=> Im(z) <= &0`,
1182 GEN_TAC THEN MP_TAC(ISPECL [`Cx(&1)`; `z:complex`] IM_COMPLEX_DIV_GE_0) THEN
1183 REWRITE_TAC[complex_div; COMPLEX_MUL_LID; IM_CNJ] THEN REAL_ARITH_TAC);;
1185 let IM_COMPLEX_INV_LE_0 = prove
1186 (`!z. Im(inv z) <= &0 <=> &0 <= Im(z)`,
1187 MESON_TAC[IM_COMPLEX_INV_GE_0; COMPLEX_INV_INV]);;
1189 let IM_COMPLEX_INV_GT_0 = prove
1190 (`!z. &0 < Im(inv z) <=> Im(z) < &0`,
1191 REWRITE_TAC[REAL_ARITH `&0 < a <=> ~(a <= &0)`; IM_COMPLEX_INV_LE_0] THEN
1194 let IM_COMPLEX_INV_LT_0 = prove
1195 (`!z. Im(inv z) < &0 <=> &0 < Im(z)`,
1196 REWRITE_TAC[REAL_ARITH `a < &0 <=> ~(&0 <= a)`; IM_COMPLEX_INV_GE_0] THEN
1199 let IM_COMPLEX_INV_EQ_0 = prove
1200 (`!z. Im(inv z) = &0 <=> Im(z) = &0`,
1201 SIMP_TAC[GSYM REAL_LE_ANTISYM; IM_COMPLEX_INV_LE_0; IM_COMPLEX_INV_GE_0] THEN
1204 let REAL_SGN_RE_COMPLEX_DIV = prove
1205 (`!w z. real_sgn(Re(w / z)) = real_sgn(Re(w * cnj z))`,
1206 REWRITE_TAC[real_sgn; RE_COMPLEX_DIV_GT_0; RE_COMPLEX_DIV_GE_0;
1207 REAL_ARITH `x < &0 <=> ~(&0 <= x)`]);;
1209 let REAL_SGN_IM_COMPLEX_DIV = prove
1210 (`!w z. real_sgn(Im(w / z)) = real_sgn(Im(w * cnj z))`,
1211 REWRITE_TAC[real_sgn; IM_COMPLEX_DIV_GT_0; IM_COMPLEX_DIV_GE_0;
1212 REAL_ARITH `x < &0 <=> ~(&0 <= x)`]);;
1214 (* ------------------------------------------------------------------------- *)
1215 (* Norm versus components for complex numbers. *)
1216 (* ------------------------------------------------------------------------- *)
1218 let COMPLEX_NORM_GE_RE_IM = prove
1219 (`!z. abs(Re(z)) <= norm(z) /\ abs(Im(z)) <= norm(z)`,
1220 GEN_TAC THEN ONCE_REWRITE_TAC[GSYM POW_2_SQRT_ABS] THEN
1221 REWRITE_TAC[complex_norm] THEN
1223 MATCH_MP_TAC SQRT_MONO_LE THEN
1224 ASM_SIMP_TAC[REAL_LE_ADDR; REAL_LE_ADDL; REAL_POW_2; REAL_LE_SQUARE]);;
1226 let COMPLEX_NORM_LE_RE_IM = prove
1227 (`!z. norm(z) <= abs(Re z) + abs(Im z)`,
1228 GEN_TAC THEN MP_TAC(ISPEC `z:complex` NORM_LE_L1) THEN
1229 REWRITE_TAC[DIMINDEX_2; SUM_2; RE_DEF; IM_DEF]);;
1231 let COMPLEX_L1_LE_NORM = prove
1232 (`!z. sqrt(&2) / &2 * (abs(Re z) + abs(Im z)) <= norm z`,
1233 GEN_TAC THEN MATCH_MP_TAC REAL_LE_LCANCEL_IMP THEN EXISTS_TAC `sqrt(&2)` THEN
1234 SIMP_TAC[REAL_ARITH `x * x / &2 * y = (x pow 2) / &2 * y`;
1235 SQRT_POW_2; REAL_POS; SQRT_POS_LT; REAL_OF_NUM_LT; ARITH] THEN
1236 MP_TAC(ISPEC `z:complex` L1_LE_NORM) THEN
1237 REWRITE_TAC[DIMINDEX_2; SUM_2; RE_DEF; IM_DEF] THEN REAL_ARITH_TAC);;
1239 (* ------------------------------------------------------------------------- *)
1240 (* Complex square roots. *)
1241 (* ------------------------------------------------------------------------- *)
1243 let csqrt = new_definition
1244 `csqrt(z) = if Im(z) = &0 then
1245 if &0 <= Re(z) then complex(sqrt(Re(z)),&0)
1246 else complex(&0,sqrt(--Re(z)))
1247 else complex(sqrt((norm(z) + Re(z)) / &2),
1248 (Im(z) / abs(Im(z))) *
1249 sqrt((norm(z) - Re(z)) / &2))`;;
1253 (`!z. csqrt(z) pow 2 = z`,
1254 GEN_TAC THEN REWRITE_TAC[COMPLEX_POW_2; csqrt] THEN COND_CASES_TAC THENL
1255 [COND_CASES_TAC THEN
1256 ASM_REWRITE_TAC[CX_DEF; complex_mul; RE; IM; REAL_MUL_RZERO; REAL_MUL_LZERO;
1257 REAL_SUB_LZERO; REAL_SUB_RZERO; REAL_ADD_LID; COMPLEX_EQ] THEN
1258 REWRITE_TAC[REAL_NEG_EQ; GSYM REAL_POW_2] THEN
1259 ASM_SIMP_TAC[SQRT_POW_2; REAL_ARITH `~(&0 <= x) ==> &0 <= --x`];
1261 REWRITE_TAC[complex_mul; RE; IM] THEN
1262 ONCE_REWRITE_TAC[REAL_ARITH
1263 `(s * s - (i * s') * (i * s') = s * s - (i * i) * (s' * s')) /\
1264 (s * i * s' + (i * s')* s = &2 * i * s * s')`] THEN
1265 REWRITE_TAC[GSYM REAL_POW_2] THEN
1266 SUBGOAL_THEN `&0 <= norm(z) + Re(z) /\ &0 <= norm(z) - Re(z)`
1267 STRIP_ASSUME_TAC THENL
1268 [MP_TAC(SPEC `z:complex` COMPLEX_NORM_GE_RE_IM) THEN REAL_ARITH_TAC;
1270 ASM_SIMP_TAC[REAL_LE_DIV; REAL_POS; GSYM SQRT_MUL; SQRT_POW_2] THEN
1271 REWRITE_TAC[COMPLEX_EQ; RE; IM] THEN CONJ_TAC THENL
1272 [ASM_SIMP_TAC[REAL_POW_DIV; REAL_POW2_ABS;
1273 REAL_POW_EQ_0; REAL_DIV_REFL] THEN
1274 REWRITE_TAC[real_div; REAL_MUL_LID; GSYM REAL_SUB_RDISTRIB] THEN
1275 REWRITE_TAC[REAL_ARITH `(m + r) - (m - r) = r * &2`] THEN
1276 REWRITE_TAC[GSYM REAL_MUL_ASSOC] THEN CONV_TAC REAL_RAT_REDUCE_CONV THEN
1277 REWRITE_TAC[REAL_MUL_RID]; ALL_TAC] THEN
1278 REWRITE_TAC[real_div] THEN
1279 ONCE_REWRITE_TAC[AC REAL_MUL_AC
1280 `(a * b) * a' * b = (a * a') * (b * b:real)`] THEN
1281 REWRITE_TAC[REAL_DIFFSQ] THEN
1282 REWRITE_TAC[complex_norm; GSYM REAL_POW_2] THEN
1283 SIMP_TAC[SQRT_POW_2; REAL_LE_ADD;
1284 REWRITE_RULE[GSYM REAL_POW_2] REAL_LE_SQUARE] THEN
1285 REWRITE_TAC[REAL_ADD_SUB; GSYM REAL_POW_MUL] THEN
1286 REWRITE_TAC[POW_2_SQRT_ABS] THEN
1287 REWRITE_TAC[REAL_ABS_MUL; REAL_ABS_INV; REAL_ABS_NUM] THEN
1288 ONCE_REWRITE_TAC[AC REAL_MUL_AC
1289 `&2 * (i * a') * a * h = i * (&2 * h) * a * a'`] THEN
1290 CONV_TAC REAL_RAT_REDUCE_CONV THEN
1291 REWRITE_TAC[REAL_MUL_LID; GSYM real_div] THEN
1292 ASM_SIMP_TAC[REAL_DIV_REFL; REAL_ABS_ZERO; REAL_MUL_RID]);;
1295 (`!x. &0 <= x ==> Cx(sqrt x) = csqrt(Cx x)`,
1296 SIMP_TAC[csqrt; IM_CX; RE_CX; COMPLEX_EQ; RE; IM]);;
1298 let CSQRT_CX = prove
1299 (`!x. &0 <= x ==> csqrt(Cx x) = Cx(sqrt x)`,
1300 SIMP_TAC[CX_SQRT]);;
1303 (`csqrt(Cx(&0)) = Cx(&0)`,
1304 SIMP_TAC[CSQRT_CX; REAL_POS; SQRT_0]);;
1307 (`csqrt(Cx(&1)) = Cx(&1)`,
1308 SIMP_TAC[CSQRT_CX; REAL_POS; SQRT_1]);;
1310 let CSQRT_PRINCIPAL = prove
1311 (`!z. &0 < Re(csqrt(z)) \/ Re(csqrt(z)) = &0 /\ &0 <= Im(csqrt(z))`,
1312 GEN_TAC THEN REWRITE_TAC[csqrt] THEN
1313 REPEAT(COND_CASES_TAC THEN ASM_REWRITE_TAC[RE; IM]) THENL
1314 [FIRST_ASSUM(MP_TAC o MATCH_MP SQRT_POS_LE) THEN REAL_ARITH_TAC;
1315 DISJ2_TAC THEN REWRITE_TAC[real_ge] THEN MATCH_MP_TAC SQRT_POS_LE THEN
1317 DISJ1_TAC THEN MATCH_MP_TAC SQRT_POS_LT THEN
1318 MATCH_MP_TAC(REAL_ARITH `abs(y) < x ==> &0 < (x + y) / &2`) THEN
1319 REWRITE_TAC[complex_norm] THEN REWRITE_TAC[GSYM POW_2_SQRT_ABS] THEN
1320 MATCH_MP_TAC SQRT_MONO_LT THEN
1321 REWRITE_TAC[REAL_POW_2; REAL_LE_SQUARE; REAL_LT_ADDR] THEN
1322 REWRITE_TAC[REAL_ARITH `&0 < x <=> &0 <= x /\ ~(x = &0)`] THEN
1323 ASM_REWRITE_TAC[REAL_LE_SQUARE; REAL_ENTIRE]]);;
1325 let RE_CSQRT = prove
1326 (`!z. &0 <= Re(csqrt z)`,
1327 MP_TAC CSQRT_PRINCIPAL THEN MATCH_MP_TAC MONO_FORALL THEN REAL_ARITH_TAC);;
1329 let CSQRT_UNIQUE = prove
1330 (`!s z. s pow 2 = z /\ (&0 < Re s \/ Re s = &0 /\ &0 <= Im s)
1332 REPEAT GEN_TAC THEN DISCH_THEN(CONJUNCTS_THEN ASSUME_TAC) THEN
1333 FIRST_X_ASSUM(SUBST_ALL_TAC o SYM) THEN
1334 MP_TAC(SPEC `(s:complex) pow 2` CSQRT) THEN
1335 SIMP_TAC[COMPLEX_RING `a pow 2 = b pow 2 <=> a = b \/ a = --b:complex`] THEN
1336 STRIP_TAC THEN ASM_REWRITE_TAC[COMPLEX_RING `--z = z <=> z = Cx(&0)`] THEN
1337 FIRST_ASSUM(MP_TAC o AP_TERM `Re`) THEN
1338 FIRST_X_ASSUM(MP_TAC o AP_TERM `Im`) THEN
1339 REWRITE_TAC[RE_NEG; IM_NEG; COMPLEX_EQ; RE_CX; IM_CX] THEN
1340 MP_TAC(SPEC `(s:complex) pow 2` CSQRT_PRINCIPAL) THEN
1341 POP_ASSUM MP_TAC THEN REAL_ARITH_TAC);;
1343 let POW_2_CSQRT = prove
1344 (`!z. &0 < Re z \/ Re(z) = &0 /\ &0 <= Im(z) ==> csqrt(z pow 2) = z`,
1345 MESON_TAC[CSQRT_UNIQUE]);;
1347 let CSQRT_EQ_0 = prove
1348 (`!z. csqrt z = Cx(&0) <=> z = Cx(&0)`,
1349 GEN_TAC THEN MP_TAC (SPEC `z:complex` CSQRT) THEN CONV_TAC COMPLEX_RING);;
1351 (* ------------------------------------------------------------------------- *)
1352 (* A few more complex-specific cases of vector notions. *)
1353 (* ------------------------------------------------------------------------- *)
1355 let COMPLEX_CMUL = prove
1356 (`!c x. c % x = Cx(c) * x`,
1357 SIMP_TAC[CART_EQ; VECTOR_MUL_COMPONENT; CX_DEF; complex;
1358 complex_mul; DIMINDEX_2; FORALL_2; IM_DEF; RE_DEF; VECTOR_2] THEN
1361 let LINEAR_COMPLEX_MUL = prove
1362 (`!c. linear (\x. c * x)`,
1363 REWRITE_TAC[linear; COMPLEX_CMUL] THEN CONV_TAC COMPLEX_RING);;
1365 let BILINEAR_COMPLEX_MUL = prove
1367 REWRITE_TAC[bilinear; linear; COMPLEX_CMUL] THEN CONV_TAC COMPLEX_RING);;
1369 let LINEAR_CNJ = prove
1371 REWRITE_TAC[linear; COMPLEX_CMUL; CNJ_ADD; CNJ_MUL; CNJ_CX]);;
1373 (* ------------------------------------------------------------------------- *)
1374 (* Complex-specific theorems about sums. *)
1375 (* ------------------------------------------------------------------------- *)
1378 (`!f s. FINITE s ==> Re(vsum s f) = sum s (\x. Re(f x))`,
1379 SIMP_TAC[RE_DEF; VSUM_COMPONENT; DIMINDEX_2; ARITH]);;
1382 (`!f s. FINITE s ==> Im(vsum s f) = sum s (\x. Im(f x))`,
1383 SIMP_TAC[IM_DEF; VSUM_COMPONENT; DIMINDEX_2; ARITH]);;
1385 let VSUM_COMPLEX_LMUL = prove
1386 (`!c f s. FINITE(s) ==> vsum s (\x. c * f x) = c * vsum s f`,
1387 GEN_TAC THEN GEN_TAC THEN MATCH_MP_TAC FINITE_INDUCT_STRONG THEN
1388 SIMP_TAC[VSUM_CLAUSES; COMPLEX_VEC_0; COMPLEX_MUL_RZERO] THEN
1389 SIMPLE_COMPLEX_ARITH_TAC);;
1391 let VSUM_COMPLEX_RMUL = prove
1392 (`!c f s. FINITE(s) ==> vsum s (\x. f x * c) = vsum s f * c`,
1393 ONCE_REWRITE_TAC[COMPLEX_MUL_SYM] THEN REWRITE_TAC[VSUM_COMPLEX_LMUL]);;
1396 (`!f:A->real s. FINITE s ==> vsum s (\a. Cx(f a)) = Cx(sum s f)`,
1397 GEN_TAC THEN MATCH_MP_TAC FINITE_INDUCT_STRONG THEN
1398 SIMP_TAC[SUM_CLAUSES; VSUM_CLAUSES; COMPLEX_VEC_0; CX_ADD]);;
1400 let CNJ_VSUM = prove
1401 (`!f s. FINITE s ==> cnj(vsum s f) = vsum s (\x. cnj(f x))`,
1402 GEN_TAC THEN MATCH_MP_TAC FINITE_INDUCT_STRONG THEN
1403 SIMP_TAC[VSUM_CLAUSES; CNJ_ADD; CNJ_CX; COMPLEX_VEC_0]);;
1405 let VSUM_CX_NUMSEG = prove
1406 (`!f m n. vsum (m..n) (\a. Cx(f a)) = Cx(sum (m..n) f)`,
1407 SIMP_TAC[VSUM_CX; FINITE_NUMSEG]);;
1409 let COMPLEX_SUB_POW = prove
1411 1 <= n ==> x pow n - y pow n =
1412 (x - y) * vsum(0..n-1) (\i. x pow i * y pow (n - 1 - i))`,
1413 SIMP_TAC[GSYM VSUM_COMPLEX_LMUL; FINITE_NUMSEG] THEN
1414 REWRITE_TAC[COMPLEX_RING
1415 `(x - y) * (a * b):complex = (x * a) * b - a * (y * b)`] THEN
1416 SIMP_TAC[GSYM complex_pow; ADD1; ARITH_RULE
1417 `1 <= n /\ x <= n - 1
1418 ==> n - 1 - x = n - (x + 1) /\ SUC(n - 1 - x) = n - x`] THEN
1419 REWRITE_TAC[VSUM_DIFFS_ALT; LE_0] THEN
1420 SIMP_TAC[SUB_0; SUB_ADD; SUB_REFL;
1421 complex_pow; COMPLEX_MUL_LID; COMPLEX_MUL_RID]);;
1423 let COMPLEX_SUB_POW_R1 = prove
1425 ==> x pow n - Cx(&1) = (x - Cx(&1)) * vsum(0..n-1) (\i. x pow i)`,
1427 DISCH_THEN(MP_TAC o SPECL [`x:complex`; `Cx(&1)`] o
1428 MATCH_MP COMPLEX_SUB_POW) THEN
1429 REWRITE_TAC[COMPLEX_POW_ONE; COMPLEX_MUL_RID]);;
1431 let COMPLEX_SUB_POW_L1 = prove
1433 ==> Cx(&1) - x pow n = (Cx(&1) - x) * vsum(0..n-1) (\i. x pow i)`,
1434 ONCE_REWRITE_TAC[GSYM COMPLEX_NEG_SUB] THEN
1435 SIMP_TAC[COMPLEX_SUB_POW_R1] THEN REWRITE_TAC[COMPLEX_MUL_LNEG]);;
1437 (* ------------------------------------------------------------------------- *)
1438 (* The complex numbers that are real (zero imaginary part). *)
1439 (* ------------------------------------------------------------------------- *)
1441 let real = new_definition
1442 `real z <=> Im z = &0`;;
1445 (`!z. real z <=> Cx(Re z) = z`,
1446 REWRITE_TAC[COMPLEX_EQ; real; CX_DEF; RE; IM] THEN REAL_ARITH_TAC);;
1448 let REAL_CNJ = prove
1449 (`!z. real z <=> cnj z = z`,
1450 REWRITE_TAC[real; cnj; COMPLEX_EQ; RE; IM] THEN REAL_ARITH_TAC);;
1452 let REAL_IMP_CNJ = prove
1453 (`!z. real z ==> cnj z = z`,
1454 REWRITE_TAC[REAL_CNJ]);;
1456 let REAL_EXISTS = prove
1457 (`!z. real z <=> ?x. z = Cx x`,
1458 MESON_TAC[REAL; real; IM_CX]);;
1460 let FORALL_REAL = prove
1461 (`(!z. real z ==> P z) <=> (!x. P(Cx x))`,
1462 MESON_TAC[REAL_EXISTS]);;
1464 let EXISTS_REAL = prove
1465 (`(?z. real z /\ P z) <=> (?x. P(Cx x))`,
1466 MESON_TAC[REAL_EXISTS]);;
1470 REWRITE_TAC[REAL_CNJ; CNJ_CX]);;
1472 let REAL_MUL_CX = prove
1473 (`!x z. real(Cx x * z) <=> x = &0 \/ real z`,
1474 REWRITE_TAC[real; IM_MUL_CX; REAL_ENTIRE]);;
1476 let REAL_ADD = prove
1477 (`!w z. real w /\ real z ==> real(w + z)`,
1478 SIMP_TAC[REAL_CNJ; CNJ_ADD]);;
1480 let REAL_NEG = prove
1481 (`!z. real z ==> real(--z)`,
1482 SIMP_TAC[REAL_CNJ; CNJ_NEG]);;
1484 let REAL_SUB = prove
1485 (`!w z. real w /\ real z ==> real(w - z)`,
1486 SIMP_TAC[REAL_CNJ; CNJ_SUB]);;
1488 let REAL_MUL = prove
1489 (`!w z. real w /\ real z ==> real(w * z)`,
1490 SIMP_TAC[REAL_CNJ; CNJ_MUL]);;
1492 let REAL_POW = prove
1493 (`!z n. real z ==> real(z pow n)`,
1494 SIMP_TAC[REAL_CNJ; CNJ_POW]);;
1496 let REAL_INV = prove
1497 (`!z. real z ==> real(inv z)`,
1498 SIMP_TAC[REAL_CNJ; CNJ_INV]);;
1500 let REAL_INV_EQ = prove
1501 (`!z. real(inv z) = real z`,
1502 MESON_TAC[REAL_INV; COMPLEX_INV_INV]);;
1504 let REAL_DIV = prove
1505 (`!w z. real w /\ real z ==> real(w / z)`,
1506 SIMP_TAC[REAL_CNJ; CNJ_DIV]);;
1508 let REAL_VSUM = prove
1509 (`!f s. FINITE s /\ (!a. a IN s ==> real(f a)) ==> real(vsum s f)`,
1510 SIMP_TAC[CNJ_VSUM; REAL_CNJ]);;
1512 let REAL_SEGMENT = prove
1513 (`!a b x. x IN segment[a,b] /\ real a /\ real b ==> real x`,
1514 SIMP_TAC[segment; IN_ELIM_THM; real; COMPLEX_EQ; LEFT_AND_EXISTS_THM;
1515 LEFT_IMP_EXISTS_THM; IM_ADD; IM_CMUL] THEN
1518 let IN_SEGMENT_CX = prove
1519 (`!a b x. Cx(x) IN segment[Cx(a),Cx(b)] <=>
1520 a <= x /\ x <= b \/ b <= x /\ x <= a`,
1521 REPEAT STRIP_TAC THEN REWRITE_TAC[segment; IN_ELIM_THM] THEN
1522 REWRITE_TAC[COMPLEX_CMUL; GSYM CX_ADD; CX_INJ; GSYM CX_MUL] THEN
1523 ASM_CASES_TAC `a:real = b` THENL
1524 [ASM_REWRITE_TAC[REAL_ARITH `(&1 - u) * b + u * b = b`] THEN
1525 ASM_CASES_TAC `x:real = b` THEN ASM_REWRITE_TAC[REAL_LE_ANTISYM] THEN
1526 EXISTS_TAC `&0` THEN REWRITE_TAC[REAL_POS];
1529 [DISCH_THEN(X_CHOOSE_THEN `u:real`
1530 (CONJUNCTS_THEN2 STRIP_ASSUME_TAC SUBST1_TAC)) THEN
1531 REWRITE_TAC[REAL_ARITH `a <= (&1 - u) * a + u * b <=> &0 <= u * (b - a)`;
1532 REAL_ARITH `b <= (&1 - u) * a + u * b <=> &0 <= (&1 - u) * (a - b)`;
1533 REAL_ARITH `(&1 - u) * a + u * b <= a <=> &0 <= u * (a - b)`;
1534 REAL_ARITH `(&1 - u) * a + u * b <= b <=> &0 <= (&1 - u) * (b - a)`] THEN
1535 DISJ_CASES_TAC(REAL_ARITH `a <= b \/ b <= a`) THENL
1536 [DISJ1_TAC; DISJ2_TAC] THEN
1537 CONJ_TAC THEN MATCH_MP_TAC REAL_LE_MUL THEN
1541 [SUBGOAL_THEN `&0 < b - a` ASSUME_TAC THENL
1542 [ASM_REAL_ARITH_TAC;
1543 EXISTS_TAC `(x - a:real) / (b - a)`];
1544 SUBGOAL_THEN `&0 < a - b` ASSUME_TAC THENL
1545 [ASM_REAL_ARITH_TAC;
1546 EXISTS_TAC `(a - x:real) / (a - b)`]] THEN
1548 [ALL_TAC; UNDISCH_TAC `~(a:real = b)` THEN CONV_TAC REAL_FIELD]) THEN
1549 ASM_SIMP_TAC[REAL_LE_LDIV_EQ; REAL_LE_RDIV_EQ] THEN
1550 ASM_REAL_ARITH_TAC);;
1552 let IN_SEGMENT_CX_GEN = prove
1554 x IN segment[Cx a,Cx b] <=>
1555 Im(x) = &0 /\ (a <= Re x /\ Re x <= b \/ b <= Re x /\ Re x <= a)`,
1556 REPEAT STRIP_TAC THEN REWRITE_TAC[GSYM real] THEN
1557 ASM_CASES_TAC `real x` THENL
1558 [FIRST_X_ASSUM(SUBST1_TAC o SYM o REWRITE_RULE[REAL]) THEN
1559 REWRITE_TAC[IN_SEGMENT_CX; REAL_CX; RE_CX] THEN REAL_ARITH_TAC;
1560 ASM_MESON_TAC[REAL_SEGMENT; REAL_CX]]);;
1562 let RE_POS_SEGMENT = prove
1563 (`!a b x. x IN segment[a,b] /\ &0 < Re a /\ &0 < Re b ==> &0 < Re x`,
1564 SIMP_TAC[segment; IN_ELIM_THM; real; COMPLEX_EQ; LEFT_AND_EXISTS_THM;
1565 LEFT_IMP_EXISTS_THM; RE_ADD; RE_CMUL] THEN
1566 REPEAT STRIP_TAC THEN MATCH_MP_TAC(REAL_ARITH
1567 `&0 <= x /\ &0 <= y /\ ~(x = &0 /\ y = &0) ==> &0 < x + y`) THEN
1568 ASM_SIMP_TAC[REAL_LE_MUL; REAL_SUB_LE; REAL_LT_IMP_LE; REAL_ENTIRE] THEN
1569 ASM_REAL_ARITH_TAC);;
1571 let CONVEX_REAL = prove
1573 REWRITE_TAC[convex; IN; COMPLEX_CMUL] THEN
1574 SIMP_TAC[REAL_ADD; REAL_MUL; REAL_CX]);;
1576 let IMAGE_CX = prove
1577 (`!s. IMAGE Cx s = {z | real z /\ Re(z) IN s}`,
1578 REWRITE_TAC[EXTENSION; IN_ELIM_THM; IN_IMAGE] THEN MESON_TAC[RE_CX; REAL]);;
1580 (* ------------------------------------------------------------------------- *)
1581 (* Useful bound-type theorems for real quantities. *)
1582 (* ------------------------------------------------------------------------- *)
1584 let REAL_NORM = prove
1585 (`!z. real z ==> norm(z) = abs(Re z)`,
1586 SIMP_TAC[real; complex_norm] THEN CONV_TAC REAL_RAT_REDUCE_CONV THEN
1587 REWRITE_TAC[POW_2_SQRT_ABS; REAL_ADD_RID]);;
1589 let REAL_NORM_POS = prove
1590 (`!z. real z /\ &0 <= Re z ==> norm(z) = Re(z)`,
1591 SIMP_TAC[REAL_NORM] THEN REAL_ARITH_TAC);;
1593 let COMPLEX_NORM_VSUM_SUM_RE = prove
1594 (`!f s. FINITE s /\ (!x. x IN s ==> real(f x) /\ &0 <= Re(f x))
1595 ==> norm(vsum s f) = sum s (\x. Re(f x))`,
1596 SIMP_TAC[GSYM RE_VSUM] THEN REPEAT STRIP_TAC THEN
1597 MATCH_MP_TAC REAL_NORM_POS THEN
1598 ASM_SIMP_TAC[REAL_VSUM; RE_VSUM; SUM_POS_LE]);;
1600 let COMPLEX_NORM_VSUM_BOUND = prove
1601 (`!s f:A->complex g:A->complex.
1602 FINITE s /\ (!x. x IN s ==> real(g x) /\ norm(f x) <= Re(g x))
1603 ==> norm(vsum s f) <= norm(vsum s g)`,
1604 REPEAT STRIP_TAC THEN MATCH_MP_TAC REAL_LE_TRANS THEN
1605 EXISTS_TAC `sum s (\x. norm((f:A->complex) x))` THEN
1606 ASM_SIMP_TAC[VSUM_NORM] THEN
1607 MATCH_MP_TAC REAL_LE_TRANS THEN
1608 EXISTS_TAC `sum s (\x. Re((g:A->complex) x))` THEN
1609 ASM_SIMP_TAC[SUM_LE] THEN
1610 MATCH_MP_TAC(REAL_ARITH `x:real = y ==> y <= x`) THEN
1611 MATCH_MP_TAC COMPLEX_NORM_VSUM_SUM_RE THEN
1612 ASM_MESON_TAC[REAL_LE_TRANS; NORM_POS_LE]);;
1614 let COMPLEX_NORM_VSUM_BOUND_SUBSET = prove
1615 (`!f:A->complex g:A->complex s t.
1616 FINITE s /\ t SUBSET s /\
1617 (!x. x IN s ==> real(g x) /\ norm(f x) <= Re(g x))
1618 ==> norm(vsum t f) <= norm(vsum s g)`,
1619 REPEAT STRIP_TAC THEN MATCH_MP_TAC REAL_LE_TRANS THEN
1620 EXISTS_TAC `norm(vsum t (g:A->complex))` THEN CONJ_TAC THENL
1621 [ASM_MESON_TAC[COMPLEX_NORM_VSUM_BOUND; SUBSET; FINITE_SUBSET];ALL_TAC] THEN
1623 `norm(vsum t (g:A->complex)) = sum t (\x. Re(g x)) /\
1624 norm(vsum s g) = sum s (\x. Re(g x))`
1625 (CONJUNCTS_THEN SUBST1_TAC)
1627 [CONJ_TAC THEN MATCH_MP_TAC COMPLEX_NORM_VSUM_SUM_RE;
1628 MATCH_MP_TAC SUM_SUBSET THEN REWRITE_TAC[IN_DIFF]] THEN
1629 ASM_MESON_TAC[REAL_LE_TRANS; NORM_POS_LE; FINITE_SUBSET; SUBSET]);;
1631 (* ------------------------------------------------------------------------- *)
1632 (* Geometric progression. *)
1633 (* ------------------------------------------------------------------------- *)
1635 let VSUM_GP_BASIC = prove
1636 (`!x n. (Cx(&1) - x) * vsum(0..n) (\i. x pow i) = Cx(&1) - x pow (SUC n)`,
1637 GEN_TAC THEN INDUCT_TAC THEN REWRITE_TAC[VSUM_CLAUSES_NUMSEG] THEN
1638 REWRITE_TAC[complex_pow; COMPLEX_MUL_RID; LE_0] THEN
1639 ASM_REWRITE_TAC[COMPLEX_ADD_LDISTRIB; complex_pow] THEN
1640 SIMPLE_COMPLEX_ARITH_TAC);;
1642 let VSUM_GP_MULTIPLIED = prove
1644 ==> ((Cx(&1) - x) * vsum(m..n) (\i. x pow i) =
1645 x pow m - x pow (SUC n))`,
1646 REPEAT STRIP_TAC THEN
1647 ASM_SIMP_TAC[VSUM_OFFSET_0; COMPLEX_POW_ADD; FINITE_NUMSEG;
1648 COMPLEX_MUL_ASSOC; VSUM_GP_BASIC; VSUM_COMPLEX_RMUL] THEN
1649 REWRITE_TAC[COMPLEX_SUB_RDISTRIB; GSYM COMPLEX_POW_ADD; COMPLEX_MUL_LID] THEN
1650 ASM_SIMP_TAC[ARITH_RULE `m <= n ==> (SUC(n - m) + m = SUC n)`]);;
1654 vsum(m..n) (\i. x pow i) =
1655 if n < m then Cx(&0)
1656 else if x = Cx(&1) then Cx(&((n + 1) - m))
1657 else (x pow m - x pow (SUC n)) / (Cx(&1) - x)`,
1659 DISJ_CASES_TAC(ARITH_RULE `n < m \/ ~(n < m) /\ m <= n:num`) THEN
1660 ASM_SIMP_TAC[VSUM_TRIV_NUMSEG; COMPLEX_VEC_0] THEN COND_CASES_TAC THENL
1661 [ASM_REWRITE_TAC[COMPLEX_POW_ONE; VSUM_CONST_NUMSEG; COMPLEX_MUL_RID];
1663 REWRITE_TAC[COMPLEX_CMUL; COMPLEX_MUL_RID] THEN
1664 MATCH_MP_TAC(COMPLEX_FIELD
1665 `~(z = Cx(&1)) /\ (Cx(&1) - z) * x = y ==> x = y / (Cx(&1) - z)`) THEN
1666 ASM_SIMP_TAC[COMPLEX_DIV_LMUL; COMPLEX_SUB_0; VSUM_GP_MULTIPLIED]);;
1668 let VSUM_GP_OFFSET = prove
1669 (`!x m n. vsum(m..m+n) (\i. x pow i) =
1670 if x = Cx(&1) then Cx(&n) + Cx(&1)
1671 else x pow m * (Cx(&1) - x pow (SUC n)) / (Cx(&1) - x)`,
1672 REPEAT GEN_TAC THEN REWRITE_TAC[VSUM_GP; ARITH_RULE `~(m + n < m:num)`] THEN
1673 COND_CASES_TAC THEN ASM_REWRITE_TAC[] THENL
1674 [REWRITE_TAC[REAL_OF_NUM_ADD; GSYM CX_ADD] THEN
1675 AP_TERM_TAC THEN AP_TERM_TAC THEN ARITH_TAC;
1676 REWRITE_TAC[complex_div; complex_pow; COMPLEX_POW_ADD] THEN
1677 SIMPLE_COMPLEX_ARITH_TAC]);;
1679 (* ------------------------------------------------------------------------- *)
1680 (* Basics about polynomial functions: extremal behaviour and root counts. *)
1681 (* ------------------------------------------------------------------------- *)
1683 let COMPLEX_SUB_POLYFUN = prove
1686 ==> vsum(0..n) (\i. a i * x pow i) - vsum(0..n) (\i. a i * y pow i) =
1688 vsum(0..n-1) (\j. vsum(j+1..n) (\i. a i * y pow (i - j - 1)) * x pow j)`,
1689 REPEAT STRIP_TAC THEN
1690 REWRITE_TAC[GSYM VSUM_SUB_NUMSEG; GSYM COMPLEX_SUB_LDISTRIB] THEN
1691 GEN_REWRITE_TAC LAND_CONV [MATCH_MP VSUM_CLAUSES_LEFT (SPEC_ALL LE_0)] THEN
1692 REWRITE_TAC[COMPLEX_SUB_REFL; complex_pow; COMPLEX_MUL_RZERO;
1693 COMPLEX_ADD_LID] THEN
1694 SIMP_TAC[COMPLEX_SUB_POW; ADD_CLAUSES] THEN
1695 ONCE_REWRITE_TAC[COMPLEX_RING `a * x * s:complex = x * a * s`] THEN
1696 SIMP_TAC[VSUM_COMPLEX_LMUL; FINITE_NUMSEG] THEN AP_TERM_TAC THEN
1697 SIMP_TAC[GSYM VSUM_COMPLEX_LMUL; GSYM VSUM_COMPLEX_RMUL; FINITE_NUMSEG;
1698 VSUM_VSUM_PRODUCT; FINITE_NUMSEG] THEN
1699 MATCH_MP_TAC VSUM_EQ_GENERAL_INVERSES THEN
1700 REPEAT(EXISTS_TAC `\(x:num,y:num). (y,x)`) THEN
1701 REWRITE_TAC[FORALL_IN_GSPEC; IN_ELIM_PAIR_THM; IN_NUMSEG] THEN
1702 REWRITE_TAC[ARITH_RULE `a - b - c:num = a - (b + c)`; ADD_SYM] THEN
1703 REWRITE_TAC[COMPLEX_MUL_AC] THEN ARITH_TAC);;
1705 let COMPLEX_SUB_POLYFUN_ALT = prove
1708 ==> vsum(0..n) (\i. a i * x pow i) - vsum(0..n) (\i. a i * y pow i) =
1710 vsum(0..n-1) (\j. vsum(0..n-j-1) (\k. a(j+k+1) * y pow k) * x pow j)`,
1711 REPEAT STRIP_TAC THEN ASM_SIMP_TAC[COMPLEX_SUB_POLYFUN] THEN AP_TERM_TAC THEN
1712 MATCH_MP_TAC VSUM_EQ_NUMSEG THEN X_GEN_TAC `j:num` THEN REPEAT STRIP_TAC THEN
1713 REWRITE_TAC[] THEN AP_THM_TAC THEN AP_TERM_TAC THEN
1714 MATCH_MP_TAC VSUM_EQ_GENERAL_INVERSES THEN
1715 MAP_EVERY EXISTS_TAC
1716 [`\i. i - (j + 1)`; `\k. j + k + 1`] THEN
1717 REWRITE_TAC[IN_NUMSEG] THEN REPEAT STRIP_TAC THEN
1718 TRY(BINOP_TAC THEN AP_TERM_TAC) THEN ASM_ARITH_TAC);;
1720 let COMPLEX_POLYFUN_LINEAR_FACTOR = prove
1721 (`!a c n. ?b. !z. vsum(0..n) (\i. c(i) * z pow i) =
1722 (z - a) * vsum(0..n-1) (\i. b(i) * z pow i) +
1723 vsum(0..n) (\i. c(i) * a pow i)`,
1724 REPEAT GEN_TAC THEN REWRITE_TAC[GSYM COMPLEX_EQ_SUB_RADD] THEN
1725 ASM_CASES_TAC `n = 0` THENL
1726 [EXISTS_TAC `\i:num. Cx(&0)` THEN
1727 ASM_SIMP_TAC[VSUM_SING; NUMSEG_SING; complex_pow; COMPLEX_MUL_LZERO] THEN
1728 REWRITE_TAC[COMPLEX_SUB_REFL; GSYM COMPLEX_VEC_0; VSUM_0] THEN
1729 REWRITE_TAC[COMPLEX_VEC_0; COMPLEX_MUL_RZERO];
1730 ASM_SIMP_TAC[COMPLEX_SUB_POLYFUN; LE_1] THEN
1731 EXISTS_TAC `\j. vsum (j + 1..n) (\i. c i * a pow (i - j - 1))` THEN
1734 let COMPLEX_POLYFUN_LINEAR_FACTOR_ROOT = prove
1735 (`!a c n. vsum(0..n) (\i. c(i) * a pow i) = Cx(&0)
1736 ==> ?b. !z. vsum(0..n) (\i. c(i) * z pow i) =
1737 (z - a) * vsum(0..n-1) (\i. b(i) * z pow i)`,
1738 MESON_TAC[COMPLEX_POLYFUN_LINEAR_FACTOR; COMPLEX_ADD_RID]);;
1740 let COMPLEX_POLYFUN_EXTREMAL_LEMMA = prove
1742 ==> ?M. !z. M <= norm(z)
1743 ==> norm(vsum(0..n) (\i. c(i) * z pow i))
1744 <= e * norm(z) pow (n + 1)`,
1745 GEN_TAC THEN INDUCT_TAC THEN SIMP_TAC[VSUM_CLAUSES_NUMSEG; LE_0] THEN
1746 REPEAT STRIP_TAC THENL
1747 [REWRITE_TAC[ADD_CLAUSES; complex_pow; REAL_POW_1; COMPLEX_MUL_RID] THEN
1748 EXISTS_TAC `norm(c 0:complex) / e` THEN ASM_SIMP_TAC[REAL_LE_LDIV_EQ] THEN
1749 REWRITE_TAC[REAL_MUL_AC];
1751 FIRST_X_ASSUM(MP_TAC o C MATCH_MP (REAL_ARITH `&0 < &1 / &2`)) THEN
1752 DISCH_THEN(X_CHOOSE_TAC `M:real`) THEN
1753 EXISTS_TAC `max M ((&1 / &2 + norm(c(n+1):complex)) / e)` THEN
1754 X_GEN_TAC `z:complex` THEN REWRITE_TAC[REAL_MAX_LE] THEN STRIP_TAC THEN
1755 FIRST_X_ASSUM(MP_TAC o SPEC `z:complex`) THEN ASM_REWRITE_TAC[] THEN
1756 MATCH_MP_TAC(NORM_ARITH
1757 `a + norm(y) <= b ==> norm(x) <= a ==> norm(x + y) <= b`) THEN
1758 SIMP_TAC[ADD1; COMPLEX_NORM_MUL; COMPLEX_NORM_POW;
1759 GSYM REAL_ADD_RDISTRIB; ARITH_RULE `(n + 1) + 1 = 1 + n + 1`] THEN
1760 GEN_REWRITE_TAC (RAND_CONV o RAND_CONV) [REAL_POW_ADD] THEN
1761 REWRITE_TAC[REAL_MUL_ASSOC] THEN MATCH_MP_TAC REAL_LE_RMUL THEN
1762 ONCE_REWRITE_TAC[REAL_MUL_SYM] THEN
1763 ASM_SIMP_TAC[GSYM REAL_LE_LDIV_EQ; REAL_POW_LE; NORM_POS_LE; REAL_POW_1]);;
1765 let COMPLEX_POLYFUN_EXTREMAL = prove
1766 (`!c n. (!k. k IN 1..n ==> c(k) = Cx(&0)) \/
1767 !B. eventually (\z. norm(vsum(0..n) (\i. c(i) * z pow i)) >= B)
1769 GEN_TAC THEN MATCH_MP_TAC num_WF THEN X_GEN_TAC `n:num` THEN DISCH_TAC THEN
1770 ASM_CASES_TAC `n = 0` THEN
1771 ASM_REWRITE_TAC[NUMSEG_CLAUSES; ARITH; NOT_IN_EMPTY] THEN
1772 MP_TAC(ARITH_RULE `0 <= n`) THEN SIMP_TAC[GSYM NUMSEG_RREC] THEN
1773 DISCH_THEN(K ALL_TAC) THEN ASM_CASES_TAC `c(n:num) = Cx(&0)` THENL
1774 [FIRST_X_ASSUM(MP_TAC o SPEC `n - 1`) THEN
1775 ANTS_TAC THENL [ASM_ARITH_TAC; ALL_TAC] THEN
1776 ASM_SIMP_TAC[GSYM NUMSEG_RREC; LE_1] THEN
1777 SIMP_TAC[IN_INSERT; VSUM_CLAUSES; FINITE_NUMSEG; IN_NUMSEG] THEN
1778 ASM_REWRITE_TAC[COMPLEX_MUL_LZERO; COMPLEX_ADD_LID; COND_ID] THEN
1780 DISJ2_TAC THEN MP_TAC(ISPECL
1781 [`c:num->complex`; `n - 1`; `norm(c(n:num):complex) / &2`]
1782 COMPLEX_POLYFUN_EXTREMAL_LEMMA) THEN ASM_SIMP_TAC[SUB_ADD; LE_1] THEN
1783 ASM_SIMP_TAC[COMPLEX_NORM_NZ; REAL_LT_DIV; REAL_OF_NUM_LT; ARITH] THEN
1784 SIMP_TAC[IN_INSERT; VSUM_CLAUSES; FINITE_NUMSEG; IN_NUMSEG] THEN
1785 ASM_SIMP_TAC[ARITH_RULE `~(n = 0) ==> ~(n <= n - 1)`] THEN
1786 DISCH_THEN(X_CHOOSE_TAC `M:real`) THEN X_GEN_TAC `B:real` THEN
1787 REWRITE_TAC[EVENTUALLY_AT_INFINITY] THEN EXISTS_TAC
1788 `max M (max (&1) ((abs B + &1) / (norm(c(n:num):complex) / &2)))` THEN
1789 X_GEN_TAC `z:complex` THEN REWRITE_TAC[real_ge; REAL_MAX_LE] THEN
1790 STRIP_TAC THEN FIRST_X_ASSUM(MP_TAC o SPEC `z:complex`) THEN
1791 ASM_REWRITE_TAC[] THEN MATCH_MP_TAC(NORM_ARITH
1792 `abs b + &1 <= norm(y) - a ==> norm(x) <= a ==> b <= norm(y + x)`) THEN
1793 REWRITE_TAC[COMPLEX_NORM_MUL; COMPLEX_NORM_POW] THEN
1794 REWRITE_TAC[REAL_ARITH `c * x - c / &2 * x = x * c / &2`] THEN
1795 ASM_SIMP_TAC[GSYM REAL_LE_LDIV_EQ; COMPLEX_NORM_NZ; REAL_LT_DIV;
1796 REAL_OF_NUM_LT; ARITH] THEN
1797 MATCH_MP_TAC REAL_LE_TRANS THEN EXISTS_TAC `norm(z:complex) pow 1` THEN
1798 CONJ_TAC THENL [ASM_REWRITE_TAC[REAL_POW_1]; ALL_TAC] THEN
1799 MATCH_MP_TAC REAL_POW_MONO THEN ASM_SIMP_TAC[LE_1]]);;
1801 let COMPLEX_POLYFUN_ROOTBOUND = prove
1802 (`!n c. ~(!i. i IN 0..n ==> c(i) = Cx(&0))
1803 ==> FINITE {z | vsum(0..n) (\i. c(i) * z pow i) = Cx(&0)} /\
1804 CARD {z | vsum(0..n) (\i. c(i) * z pow i) = Cx(&0)} <= n`,
1805 REWRITE_TAC[TAUT `~a ==> b <=> a \/ b`] THEN INDUCT_TAC THEN GEN_TAC THENL
1806 [SIMP_TAC[NUMSEG_SING; VSUM_SING; IN_SING; complex_pow] THEN
1807 ASM_CASES_TAC `c 0 = Cx(&0)` THEN ASM_REWRITE_TAC[COMPLEX_MUL_RID] THEN
1808 REWRITE_TAC[EMPTY_GSPEC; FINITE_RULES; CARD_CLAUSES; LE_REFL];
1810 ASM_CASES_TAC `{z | vsum(0..SUC n) (\i. c(i) * z pow i) = Cx(&0)} = {}` THEN
1811 ASM_REWRITE_TAC[FINITE_RULES; CARD_CLAUSES; LE_0] THEN
1812 FIRST_X_ASSUM(X_CHOOSE_THEN `a:complex` MP_TAC o
1813 GEN_REWRITE_RULE I [GSYM MEMBER_NOT_EMPTY]) THEN
1814 REWRITE_TAC[IN_ELIM_THM] THEN DISCH_TAC THEN
1815 FIRST_ASSUM(MP_TAC o MATCH_MP COMPLEX_POLYFUN_LINEAR_FACTOR_ROOT) THEN
1816 DISCH_THEN(X_CHOOSE_TAC `b:num->complex`) THEN
1817 ASM_REWRITE_TAC[COMPLEX_ENTIRE; COMPLEX_SUB_0; SUC_SUB1; SET_RULE
1818 `{z | z = a \/ P z} = a INSERT {z | P z}`] THEN
1819 FIRST_X_ASSUM(MP_TAC o SPEC `b:num->complex`) THEN
1820 STRIP_TAC THEN ASM_SIMP_TAC[CARD_CLAUSES; FINITE_RULES] THENL
1821 [DISJ1_TAC; ASM_ARITH_TAC] THEN
1822 MP_TAC(SPECL [`c:num->complex`; `SUC n`] COMPLEX_POLYFUN_EXTREMAL) THEN
1823 ASM_REWRITE_TAC[] THEN FIRST_X_ASSUM(MP_TAC o SPEC `Cx(&0)`) THEN
1824 ASM_SIMP_TAC[SUC_SUB1; COMPLEX_MUL_LZERO] THEN
1825 SIMP_TAC[COMPLEX_POW_ZERO; COND_RAND; COMPLEX_MUL_RZERO] THEN
1826 ASM_SIMP_TAC[VSUM_0; GSYM COMPLEX_VEC_0; VSUM_DELTA; IN_NUMSEG; LE_0] THEN
1827 REWRITE_TAC[COMPLEX_VEC_0; COMPLEX_MUL_RZERO; COMPLEX_NORM_NUM] THEN
1828 REWRITE_TAC[COMPLEX_MUL_RID; real_ge; EVENTUALLY_AT_INFINITY] THEN
1829 REPEAT STRIP_TAC THENL [ASM_MESON_TAC[LE_1]; ALL_TAC] THEN
1830 FIRST_X_ASSUM(MP_TAC o SPEC `&1`) THEN CONV_TAC REAL_RAT_REDUCE_CONV THEN
1831 MATCH_MP_TAC(TAUT `~a ==> a ==> b`) THEN
1832 REWRITE_TAC[NOT_EXISTS_THM; NOT_FORALL_THM] THEN X_GEN_TAC `b:real` THEN
1833 MP_TAC(SPEC `b:real` (INST_TYPE [`:2`,`:N`] VECTOR_CHOOSE_SIZE)) THEN
1834 ASM_MESON_TAC[NORM_POS_LE; REAL_LE_TOTAL; REAL_LE_TRANS]);;
1836 let COMPLEX_POLYFUN_FINITE_ROOTS = prove
1837 (`!n c. FINITE {x | vsum(0..n) (\i. c i * x pow i) = Cx(&0)} <=>
1838 ?i. i IN 0..n /\ ~(c i = Cx(&0))`,
1839 REPEAT GEN_TAC THEN REWRITE_TAC[TAUT `a /\ ~b <=> ~(a ==> b)`] THEN
1840 REWRITE_TAC[GSYM NOT_FORALL_THM] THEN EQ_TAC THEN
1841 SIMP_TAC[COMPLEX_POLYFUN_ROOTBOUND] THEN
1842 ONCE_REWRITE_TAC[GSYM CONTRAPOS_THM] THEN
1843 SIMP_TAC[COMPLEX_MUL_LZERO] THEN SIMP_TAC[GSYM COMPLEX_VEC_0; VSUM_0] THEN
1844 REWRITE_TAC[SET_RULE `{x | T} = (:complex)`; GSYM INFINITE;
1845 EUCLIDEAN_SPACE_INFINITE]);;
1847 let COMPLEX_POLYFUN_EQ_0 = prove
1848 (`!n c. (!z. vsum(0..n) (\i. c i * z pow i) = Cx(&0)) <=>
1849 (!i. i IN 0..n ==> c i = Cx(&0))`,
1850 REPEAT GEN_TAC THEN EQ_TAC THEN DISCH_TAC THENL
1851 [GEN_REWRITE_TAC I [TAUT `p <=> ~ ~p`] THEN DISCH_THEN(MP_TAC o MATCH_MP
1852 COMPLEX_POLYFUN_ROOTBOUND) THEN
1853 ASM_REWRITE_TAC[EUCLIDEAN_SPACE_INFINITE; GSYM INFINITE; DE_MORGAN_THM;
1854 SET_RULE `{x | T} = (:complex)`];
1855 ASM_SIMP_TAC[IN_NUMSEG; LE_0; COMPLEX_MUL_LZERO] THEN
1856 REWRITE_TAC[GSYM COMPLEX_VEC_0; VSUM_0]]);;
1858 let COMPLEX_POLYFUN_EQ_CONST = prove
1859 (`!n c k. (!z. vsum(0..n) (\i. c i * z pow i) = k) <=>
1860 c 0 = k /\ (!i. i IN 1..n ==> c i = Cx(&0))`,
1861 REPEAT GEN_TAC THEN MATCH_MP_TAC EQ_TRANS THEN EXISTS_TAC
1862 `!x. vsum(0..n) (\i. (if i = 0 then c 0 - k else c i) * x pow i) =
1865 [SIMP_TAC[VSUM_CLAUSES_LEFT; LE_0; complex_pow; COMPLEX_MUL_RID] THEN
1866 REWRITE_TAC[COMPLEX_RING `(c - k) + s = Cx(&0) <=> c + s = k`] THEN
1867 AP_TERM_TAC THEN ABS_TAC THEN AP_THM_TAC THEN AP_TERM_TAC THEN
1868 AP_TERM_TAC THEN MATCH_MP_TAC VSUM_EQ THEN GEN_TAC THEN
1869 REWRITE_TAC[IN_NUMSEG] THEN
1870 COND_CASES_TAC THEN ASM_REWRITE_TAC[ARITH];
1871 REWRITE_TAC[COMPLEX_POLYFUN_EQ_0; IN_NUMSEG; LE_0] THEN
1872 GEN_REWRITE_TAC LAND_CONV [MESON[]
1873 `(!n. P n) <=> P 0 /\ (!n. ~(n = 0) ==> P n)`] THEN
1874 SIMP_TAC[LE_0; COMPLEX_SUB_0] THEN MESON_TAC[LE_1]]);;
1876 (* ------------------------------------------------------------------------- *)
1877 (* Complex products. *)
1878 (* ------------------------------------------------------------------------- *)
1880 let cproduct = new_definition
1881 `cproduct = iterate (( * ):complex->complex->complex)`;;
1883 let NEUTRAL_COMPLEX_MUL = prove
1884 (`neutral(( * ):complex->complex->complex) = Cx(&1)`,
1885 REWRITE_TAC[neutral] THEN MATCH_MP_TAC SELECT_UNIQUE THEN
1886 MESON_TAC[COMPLEX_MUL_LID; COMPLEX_MUL_RID]);;
1888 let MONOIDAL_COMPLEX_MUL = prove
1889 (`monoidal(( * ):complex->complex->complex)`,
1890 REWRITE_TAC[monoidal; NEUTRAL_COMPLEX_MUL] THEN SIMPLE_COMPLEX_ARITH_TAC);;
1892 let CPRODUCT_CLAUSES = prove
1893 (`(!f. cproduct {} f = Cx(&1)) /\
1895 ==> (cproduct (x INSERT s) f =
1896 if x IN s then cproduct s f else f(x) * cproduct s f))`,
1897 REWRITE_TAC[cproduct; GSYM NEUTRAL_COMPLEX_MUL] THEN
1898 ONCE_REWRITE_TAC[SWAP_FORALL_THM] THEN
1899 MATCH_MP_TAC ITERATE_CLAUSES THEN REWRITE_TAC[MONOIDAL_COMPLEX_MUL]);;
1901 let CPRODUCT_EQ_0 = prove
1902 (`!f s. FINITE s ==> (cproduct s f = Cx(&0) <=> ?x. x IN s /\ f(x) = Cx(&0))`,
1903 GEN_TAC THEN MATCH_MP_TAC FINITE_INDUCT_STRONG THEN
1904 SIMP_TAC[CPRODUCT_CLAUSES; COMPLEX_ENTIRE; IN_INSERT; CX_INJ; REAL_OF_NUM_EQ;
1905 ARITH; NOT_IN_EMPTY] THEN
1908 let CPRODUCT_INV = prove
1909 (`!f s. FINITE s ==> cproduct s (\x. inv(f x)) = inv(cproduct s f)`,
1910 GEN_TAC THEN MATCH_MP_TAC FINITE_INDUCT_STRONG THEN
1911 SIMP_TAC[CPRODUCT_CLAUSES; COMPLEX_INV_1; COMPLEX_INV_MUL]);;
1913 let CPRODUCT_MUL = prove
1915 ==> cproduct s (\x. f x * g x) = cproduct s f * cproduct s g`,
1916 GEN_TAC THEN GEN_TAC THEN MATCH_MP_TAC FINITE_INDUCT_STRONG THEN
1917 SIMP_TAC[CPRODUCT_CLAUSES; COMPLEX_MUL_AC; COMPLEX_MUL_LID]);;
1919 let CPRODUCT_EQ_1 = prove
1920 (`!f s. (!x:A. x IN s ==> (f(x) = Cx(&1))) ==> (cproduct s f = Cx(&1))`,
1921 REWRITE_TAC[cproduct; GSYM NEUTRAL_COMPLEX_MUL] THEN
1922 SIMP_TAC[ITERATE_EQ_NEUTRAL; MONOIDAL_COMPLEX_MUL]);;
1924 let CPRODUCT_1 = prove
1925 (`!s. cproduct s (\n. Cx(&1)) = Cx(&1)`,
1926 SIMP_TAC[CPRODUCT_EQ_1]);;
1928 let CPRODUCT_POW = prove
1930 ==> cproduct s (\x. f x pow n) = (cproduct s f) pow n`,
1931 GEN_TAC THEN GEN_TAC THEN REWRITE_TAC[RIGHT_FORALL_IMP_THM] THEN
1932 DISCH_TAC THEN INDUCT_TAC THEN
1933 ASM_SIMP_TAC[complex_pow; CPRODUCT_MUL; CPRODUCT_1]);;
1935 let NORM_CPRODUCT = prove
1936 (`!f s. FINITE s ==> norm(cproduct s f) = product s (\x. norm(f x))`,
1937 GEN_TAC THEN MATCH_MP_TAC FINITE_INDUCT_STRONG THEN
1938 SIMP_TAC[CPRODUCT_CLAUSES; COMPLEX_NORM_CX; REAL_ABS_NUM;
1939 CPRODUCT_MUL; PRODUCT_CLAUSES; COMPLEX_NORM_MUL]);;
1941 let CPRODUCT_EQ = prove
1942 (`!f g s. (!x. x IN s ==> (f x = g x)) ==> cproduct s f = cproduct s g`,
1943 REWRITE_TAC[cproduct] THEN MATCH_MP_TAC ITERATE_EQ THEN
1944 REWRITE_TAC[MONOIDAL_COMPLEX_MUL]);;