1 (* Title: HOL/Rational.thy
2 Author: Markus Wenzel, TU Muenchen
5 header {* Rational numbers *}
8 imports GCD Archimedean_Field
11 subsection {* Rational numbers as quotient *}
13 subsubsection {* Construction of the type of rational numbers *}
16 ratrel :: "((int \<times> int) \<times> (int \<times> int)) set" where
17 "ratrel = {(x, y). snd x \<noteq> 0 \<and> snd y \<noteq> 0 \<and> fst x * snd y = fst y * snd x}"
19 lemma ratrel_iff [simp]:
20 "(x, y) \<in> ratrel \<longleftrightarrow> snd x \<noteq> 0 \<and> snd y \<noteq> 0 \<and> fst x * snd y = fst y * snd x"
21 by (simp add: ratrel_def)
23 lemma refl_on_ratrel: "refl_on {x. snd x \<noteq> 0} ratrel"
24 by (auto simp add: refl_on_def ratrel_def)
26 lemma sym_ratrel: "sym ratrel"
27 by (simp add: ratrel_def sym_def)
29 lemma trans_ratrel: "trans ratrel"
30 proof (rule transI, unfold split_paired_all)
31 fix a b a' b' a'' b'' :: int
32 assume A: "((a, b), (a', b')) \<in> ratrel"
33 assume B: "((a', b'), (a'', b'')) \<in> ratrel"
34 have "b' * (a * b'') = b'' * (a * b')" by simp
35 also from A have "a * b' = a' * b" by auto
36 also have "b'' * (a' * b) = b * (a' * b'')" by simp
37 also from B have "a' * b'' = a'' * b'" by auto
38 also have "b * (a'' * b') = b' * (a'' * b)" by simp
39 finally have "b' * (a * b'') = b' * (a'' * b)" .
40 moreover from B have "b' \<noteq> 0" by auto
41 ultimately have "a * b'' = a'' * b" by simp
42 with A B show "((a, b), (a'', b'')) \<in> ratrel" by auto
45 lemma equiv_ratrel: "equiv {x. snd x \<noteq> 0} ratrel"
46 by (rule equiv.intro [OF refl_on_ratrel sym_ratrel trans_ratrel])
48 lemmas UN_ratrel = UN_equiv_class [OF equiv_ratrel]
49 lemmas UN_ratrel2 = UN_equiv_class2 [OF equiv_ratrel equiv_ratrel]
51 lemma equiv_ratrel_iff [iff]:
52 assumes "snd x \<noteq> 0" and "snd y \<noteq> 0"
53 shows "ratrel `` {x} = ratrel `` {y} \<longleftrightarrow> (x, y) \<in> ratrel"
54 by (rule eq_equiv_class_iff, rule equiv_ratrel) (auto simp add: assms)
56 typedef (Rat) rat = "{x. snd x \<noteq> 0} // ratrel"
58 have "(0::int, 1::int) \<in> {x. snd x \<noteq> 0}" by simp
59 then show "ratrel `` {(0, 1)} \<in> {x. snd x \<noteq> 0} // ratrel" by (rule quotientI)
62 lemma ratrel_in_Rat [simp]: "snd x \<noteq> 0 \<Longrightarrow> ratrel `` {x} \<in> Rat"
63 by (simp add: Rat_def quotientI)
65 declare Abs_Rat_inject [simp] Abs_Rat_inverse [simp]
68 subsubsection {* Representation and basic operations *}
71 Fract :: "int \<Rightarrow> int \<Rightarrow> rat" where
72 [code del]: "Fract a b = Abs_Rat (ratrel `` {if b = 0 then (0, 1) else (a, b)})"
76 lemma Rat_cases [case_names Fract, cases type: rat]:
77 assumes "\<And>a b. q = Fract a b \<Longrightarrow> b \<noteq> 0 \<Longrightarrow> C"
79 using assms by (cases q) (clarsimp simp add: Fract_def Rat_def quotient_def)
81 lemma Rat_induct [case_names Fract, induct type: rat]:
82 assumes "\<And>a b. b \<noteq> 0 \<Longrightarrow> P (Fract a b)"
84 using assms by (cases q) simp
87 shows "\<And>a b c d. b \<noteq> 0 \<Longrightarrow> d \<noteq> 0 \<Longrightarrow> Fract a b = Fract c d \<longleftrightarrow> a * d = c * b"
88 and "\<And>a. Fract a 0 = Fract 0 1"
89 and "\<And>a c. Fract 0 a = Fract 0 c"
90 by (simp_all add: Fract_def)
92 instantiation rat :: comm_ring_1
96 Zero_rat_def [code, code unfold]: "0 = Fract 0 1"
99 One_rat_def [code, code unfold]: "1 = Fract 1 1"
102 add_rat_def [code del]:
103 "q + r = Abs_Rat (\<Union>x \<in> Rep_Rat q. \<Union>y \<in> Rep_Rat r.
104 ratrel `` {(fst x * snd y + fst y * snd x, snd x * snd y)})"
106 lemma add_rat [simp]:
107 assumes "b \<noteq> 0" and "d \<noteq> 0"
108 shows "Fract a b + Fract c d = Fract (a * d + c * b) (b * d)"
110 have "(\<lambda>x y. ratrel``{(fst x * snd y + fst y * snd x, snd x * snd y)})
112 by (rule equiv_ratrel [THEN congruent2_commuteI]) (simp_all add: left_distrib)
113 with assms show ?thesis by (simp add: Fract_def add_rat_def UN_ratrel2)
117 minus_rat_def [code del]:
118 "- q = Abs_Rat (\<Union>x \<in> Rep_Rat q. ratrel `` {(- fst x, snd x)})"
120 lemma minus_rat [simp, code]: "- Fract a b = Fract (- a) b"
122 have "(\<lambda>x. ratrel `` {(- fst x, snd x)}) respects ratrel"
123 by (simp add: congruent_def)
124 then show ?thesis by (simp add: Fract_def minus_rat_def UN_ratrel)
127 lemma minus_rat_cancel [simp]: "Fract (- a) (- b) = Fract a b"
128 by (cases "b = 0") (simp_all add: eq_rat)
131 diff_rat_def [code del]: "q - r = q + - (r::rat)"
133 lemma diff_rat [simp]:
134 assumes "b \<noteq> 0" and "d \<noteq> 0"
135 shows "Fract a b - Fract c d = Fract (a * d - c * b) (b * d)"
136 using assms by (simp add: diff_rat_def)
139 mult_rat_def [code del]:
140 "q * r = Abs_Rat (\<Union>x \<in> Rep_Rat q. \<Union>y \<in> Rep_Rat r.
141 ratrel``{(fst x * fst y, snd x * snd y)})"
143 lemma mult_rat [simp]: "Fract a b * Fract c d = Fract (a * c) (b * d)"
145 have "(\<lambda>x y. ratrel `` {(fst x * fst y, snd x * snd y)}) respects2 ratrel"
146 by (rule equiv_ratrel [THEN congruent2_commuteI]) simp_all
147 then show ?thesis by (simp add: Fract_def mult_rat_def UN_ratrel2)
150 lemma mult_rat_cancel:
151 assumes "c \<noteq> 0"
152 shows "Fract (c * a) (c * b) = Fract a b"
154 from assms have "Fract c c = Fract 1 1" by (simp add: Fract_def)
155 then show ?thesis by (simp add: mult_rat [symmetric])
159 fix q r s :: rat show "(q * r) * s = q * (r * s)"
160 by (cases q, cases r, cases s) (simp add: eq_rat)
162 fix q r :: rat show "q * r = r * q"
163 by (cases q, cases r) (simp add: eq_rat)
165 fix q :: rat show "1 * q = q"
166 by (cases q) (simp add: One_rat_def eq_rat)
168 fix q r s :: rat show "(q + r) + s = q + (r + s)"
169 by (cases q, cases r, cases s) (simp add: eq_rat algebra_simps)
171 fix q r :: rat show "q + r = r + q"
172 by (cases q, cases r) (simp add: eq_rat)
174 fix q :: rat show "0 + q = q"
175 by (cases q) (simp add: Zero_rat_def eq_rat)
177 fix q :: rat show "- q + q = 0"
178 by (cases q) (simp add: Zero_rat_def eq_rat)
180 fix q r :: rat show "q - r = q + - r"
181 by (cases q, cases r) (simp add: eq_rat)
183 fix q r s :: rat show "(q + r) * s = q * s + r * s"
184 by (cases q, cases r, cases s) (simp add: eq_rat algebra_simps)
186 show "(0::rat) \<noteq> 1" by (simp add: Zero_rat_def One_rat_def eq_rat)
191 lemma of_nat_rat: "of_nat k = Fract (of_nat k) 1"
192 by (induct k) (simp_all add: Zero_rat_def One_rat_def)
194 lemma of_int_rat: "of_int k = Fract k 1"
195 by (cases k rule: int_diff_cases) (simp add: of_nat_rat)
197 lemma Fract_of_nat_eq: "Fract (of_nat k) 1 = of_nat k"
198 by (rule of_nat_rat [symmetric])
200 lemma Fract_of_int_eq: "Fract k 1 = of_int k"
201 by (rule of_int_rat [symmetric])
203 instantiation rat :: number_ring
207 rat_number_of_def [code del]: "number_of w = Fract w 1"
210 qed (simp add: rat_number_of_def of_int_rat)
214 lemma rat_number_collapse [code post]:
217 "Fract (number_of k) 1 = number_of k"
220 (simp_all add: Zero_rat_def One_rat_def number_of_is_id number_of_eq of_int_rat eq_rat Fract_def)
222 lemma rat_number_expand [code unfold]:
225 "number_of k = Fract (number_of k) 1"
226 by (simp_all add: rat_number_collapse)
228 lemma iszero_rat [simp]:
229 "iszero (number_of k :: rat) \<longleftrightarrow> iszero (number_of k :: int)"
230 by (simp add: iszero_def rat_number_expand number_of_is_id eq_rat)
232 lemma Rat_cases_nonzero [case_names Fract 0]:
233 assumes Fract: "\<And>a b. q = Fract a b \<Longrightarrow> b \<noteq> 0 \<Longrightarrow> a \<noteq> 0 \<Longrightarrow> C"
234 assumes 0: "q = 0 \<Longrightarrow> C"
236 proof (cases "q = 0")
237 case True then show C using 0 by auto
240 then obtain a b where "q = Fract a b" and "b \<noteq> 0" by (cases q) auto
241 moreover with False have "0 \<noteq> Fract a b" by simp
242 with `b \<noteq> 0` have "a \<noteq> 0" by (simp add: Zero_rat_def eq_rat)
243 with Fract `q = Fract a b` `b \<noteq> 0` show C by auto
247 subsubsection {* The field of rational numbers *}
249 instantiation rat :: "{field, division_by_zero}"
253 inverse_rat_def [code del]:
254 "inverse q = Abs_Rat (\<Union>x \<in> Rep_Rat q.
255 ratrel `` {if fst x = 0 then (0, 1) else (snd x, fst x)})"
257 lemma inverse_rat [simp]: "inverse (Fract a b) = Fract b a"
259 have "(\<lambda>x. ratrel `` {if fst x = 0 then (0, 1) else (snd x, fst x)}) respects ratrel"
260 by (auto simp add: congruent_def mult_commute)
261 then show ?thesis by (simp add: Fract_def inverse_rat_def UN_ratrel)
265 divide_rat_def [code del]: "q / r = q * inverse (r::rat)"
267 lemma divide_rat [simp]: "Fract a b / Fract c d = Fract (a * d) (b * c)"
268 by (simp add: divide_rat_def)
271 show "inverse 0 = (0::rat)" by (simp add: rat_number_expand)
272 (simp add: rat_number_collapse)
275 assume "q \<noteq> 0"
276 then show "inverse q * q = 1" by (cases q rule: Rat_cases_nonzero)
277 (simp_all add: mult_rat inverse_rat rat_number_expand eq_rat)
280 show "q / r = q * inverse r" by (simp add: divide_rat_def)
286 subsubsection {* Various *}
288 lemma Fract_add_one: "n \<noteq> 0 ==> Fract (m + n) n = Fract m n + 1"
289 by (simp add: rat_number_expand)
291 lemma Fract_of_int_quotient: "Fract k l = of_int k / of_int l"
292 by (simp add: Fract_of_int_eq [symmetric])
294 lemma Fract_number_of_quotient [code post]:
295 "Fract (number_of k) (number_of l) = number_of k / number_of l"
296 unfolding Fract_of_int_quotient number_of_is_id number_of_eq ..
298 lemma Fract_1_number_of [code post]:
299 "Fract 1 (number_of k) = 1 / number_of k"
300 unfolding Fract_of_int_quotient number_of_eq by simp
302 subsubsection {* The ordered field of rational numbers *}
304 instantiation rat :: linorder
308 le_rat_def [code del]:
309 "q \<le> r \<longleftrightarrow> contents (\<Union>x \<in> Rep_Rat q. \<Union>y \<in> Rep_Rat r.
310 {(fst x * snd y) * (snd x * snd y) \<le> (fst y * snd x) * (snd x * snd y)})"
313 assumes "b \<noteq> 0" and "d \<noteq> 0"
314 shows "Fract a b \<le> Fract c d \<longleftrightarrow> (a * d) * (b * d) \<le> (c * b) * (b * d)"
316 have "(\<lambda>x y. {(fst x * snd y) * (snd x * snd y) \<le> (fst y * snd x) * (snd x * snd y)})
318 proof (clarsimp simp add: congruent2_def)
319 fix a b a' b' c d c' d'::int
320 assume neq: "b \<noteq> 0" "b' \<noteq> 0" "d \<noteq> 0" "d' \<noteq> 0"
321 assume eq1: "a * b' = a' * b"
322 assume eq2: "c * d' = c' * d"
324 let ?le = "\<lambda>a b c d. ((a * d) * (b * d) \<le> (c * b) * (b * d))"
326 fix a b c d x :: int assume x: "x \<noteq> 0"
327 have "?le a b c d = ?le (a * x) (b * x) c d"
329 from x have "0 < x * x" by (auto simp add: zero_less_mult_iff)
331 ((a * d) * (b * d) * (x * x) \<le> (c * b) * (b * d) * (x * x))"
332 by (simp add: mult_le_cancel_right)
333 also have "... = ?le (a * x) (b * x) c d"
334 by (simp add: mult_ac)
335 finally show ?thesis .
337 } note le_factor = this
339 let ?D = "b * d" and ?D' = "b' * d'"
340 from neq have D: "?D \<noteq> 0" by simp
341 from neq have "?D' \<noteq> 0" by simp
342 hence "?le a b c d = ?le (a * ?D') (b * ?D') c d"
344 also have "... = ((a * b') * ?D * ?D' * d * d' \<le> (c * d') * ?D * ?D' * b * b')"
345 by (simp add: mult_ac)
346 also have "... = ((a' * b) * ?D * ?D' * d * d' \<le> (c' * d) * ?D * ?D' * b * b')"
347 by (simp only: eq1 eq2)
348 also have "... = ?le (a' * ?D) (b' * ?D) c' d'"
349 by (simp add: mult_ac)
350 also from D have "... = ?le a' b' c' d'"
351 by (rule le_factor [symmetric])
352 finally show "?le a b c d = ?le a' b' c' d'" .
354 with assms show ?thesis by (simp add: Fract_def le_rat_def UN_ratrel2)
358 less_rat_def [code del]: "z < (w::rat) \<longleftrightarrow> z \<le> w \<and> z \<noteq> w"
360 lemma less_rat [simp]:
361 assumes "b \<noteq> 0" and "d \<noteq> 0"
362 shows "Fract a b < Fract c d \<longleftrightarrow> (a * d) * (b * d) < (c * b) * (b * d)"
363 using assms by (simp add: less_rat_def eq_rat order_less_le)
368 assume "q \<le> r" and "r \<le> s"
370 proof (insert prems, induct q, induct r, induct s)
371 fix a b c d e f :: int
372 assume neq: "b \<noteq> 0" "d \<noteq> 0" "f \<noteq> 0"
373 assume 1: "Fract a b \<le> Fract c d" and 2: "Fract c d \<le> Fract e f"
374 show "Fract a b \<le> Fract e f"
376 from neq obtain bb: "0 < b * b" and dd: "0 < d * d" and ff: "0 < f * f"
377 by (auto simp add: zero_less_mult_iff linorder_neq_iff)
378 have "(a * d) * (b * d) * (f * f) \<le> (c * b) * (b * d) * (f * f)"
380 from neq 1 have "(a * d) * (b * d) \<le> (c * b) * (b * d)"
382 with ff show ?thesis by (simp add: mult_le_cancel_right)
384 also have "... = (c * f) * (d * f) * (b * b)" by algebra
385 also have "... \<le> (e * d) * (d * f) * (b * b)"
387 from neq 2 have "(c * f) * (d * f) \<le> (e * d) * (d * f)"
389 with bb show ?thesis by (simp add: mult_le_cancel_right)
391 finally have "(a * f) * (b * f) * (d * d) \<le> e * b * (b * f) * (d * d)"
392 by (simp only: mult_ac)
393 with dd have "(a * f) * (b * f) \<le> (e * b) * (b * f)"
394 by (simp add: mult_le_cancel_right)
395 with neq show ?thesis by simp
399 assume "q \<le> r" and "r \<le> q"
401 proof (insert prems, induct q, induct r)
403 assume neq: "b \<noteq> 0" "d \<noteq> 0"
404 assume 1: "Fract a b \<le> Fract c d" and 2: "Fract c d \<le> Fract a b"
405 show "Fract a b = Fract c d"
407 from neq 1 have "(a * d) * (b * d) \<le> (c * b) * (b * d)"
409 also have "... \<le> (a * d) * (b * d)"
411 from neq 2 have "(c * b) * (d * b) \<le> (a * d) * (d * b)"
413 thus ?thesis by (simp only: mult_ac)
415 finally have "(a * d) * (b * d) = (c * b) * (b * d)" .
416 moreover from neq have "b * d \<noteq> 0" by simp
417 ultimately have "a * d = c * b" by simp
418 with neq show ?thesis by (simp add: eq_rat)
424 show "(q < r) = (q \<le> r \<and> \<not> r \<le> q)"
425 by (induct q, induct r) (auto simp add: le_less mult_commute)
426 show "q \<le> r \<or> r \<le> q"
427 by (induct q, induct r)
428 (simp add: mult_commute, rule linorder_linear)
434 instantiation rat :: "{distrib_lattice, abs_if, sgn_if}"
438 abs_rat_def [code del]: "\<bar>q\<bar> = (if q < 0 then -q else (q::rat))"
440 lemma abs_rat [simp, code]: "\<bar>Fract a b\<bar> = Fract \<bar>a\<bar> \<bar>b\<bar>"
441 by (auto simp add: abs_rat_def zabs_def Zero_rat_def less_rat not_less le_less minus_rat eq_rat zero_compare_simps)
444 sgn_rat_def [code del]: "sgn (q::rat) = (if q = 0 then 0 else if 0 < q then 1 else - 1)"
446 lemma sgn_rat [simp, code]: "sgn (Fract a b) = of_int (sgn a * sgn b)"
447 unfolding Fract_of_int_eq
448 by (auto simp: zsgn_def sgn_rat_def Zero_rat_def eq_rat)
449 (auto simp: rat_number_collapse not_less le_less zero_less_mult_iff)
452 "(inf \<Colon> rat \<Rightarrow> rat \<Rightarrow> rat) = min"
455 "(sup \<Colon> rat \<Rightarrow> rat \<Rightarrow> rat) = max"
457 instance by intro_classes
458 (auto simp add: abs_rat_def sgn_rat_def min_max.sup_inf_distrib1 inf_rat_def sup_rat_def)
462 instance rat :: ordered_field
465 show "q \<le> r ==> s + q \<le> s + r"
466 proof (induct q, induct r, induct s)
467 fix a b c d e f :: int
468 assume neq: "b \<noteq> 0" "d \<noteq> 0" "f \<noteq> 0"
469 assume le: "Fract a b \<le> Fract c d"
470 show "Fract e f + Fract a b \<le> Fract e f + Fract c d"
472 let ?F = "f * f" from neq have F: "0 < ?F"
473 by (auto simp add: zero_less_mult_iff)
474 from neq le have "(a * d) * (b * d) \<le> (c * b) * (b * d)"
476 with F have "(a * d) * (b * d) * ?F * ?F \<le> (c * b) * (b * d) * ?F * ?F"
477 by (simp add: mult_le_cancel_right)
478 with neq show ?thesis by (simp add: mult_ac int_distrib)
481 show "q < r ==> 0 < s ==> s * q < s * r"
482 proof (induct q, induct r, induct s)
483 fix a b c d e f :: int
484 assume neq: "b \<noteq> 0" "d \<noteq> 0" "f \<noteq> 0"
485 assume le: "Fract a b < Fract c d"
486 assume gt: "0 < Fract e f"
487 show "Fract e f * Fract a b < Fract e f * Fract c d"
489 let ?E = "e * f" and ?F = "f * f"
490 from neq gt have "0 < ?E"
491 by (auto simp add: Zero_rat_def order_less_le eq_rat)
492 moreover from neq have "0 < ?F"
493 by (auto simp add: zero_less_mult_iff)
494 moreover from neq le have "(a * d) * (b * d) < (c * b) * (b * d)"
496 ultimately have "(a * d) * (b * d) * ?E * ?F < (c * b) * (b * d) * ?E * ?F"
497 by (simp add: mult_less_cancel_right)
498 with neq show ?thesis
499 by (simp add: mult_ac)
504 lemma Rat_induct_pos [case_names Fract, induct type: rat]:
505 assumes step: "\<And>a b. 0 < b \<Longrightarrow> P (Fract a b)"
508 have step': "\<And>a b. b < 0 \<Longrightarrow> P (Fract a b)"
510 fix a::int and b::int
512 hence "0 < -b" by simp
513 hence "P (Fract (-a) (-b))" by (rule step)
514 thus "P (Fract a b)" by (simp add: order_less_imp_not_eq [OF b])
517 thus "P q" by (force simp add: linorder_neq_iff step step')
520 lemma zero_less_Fract_iff:
521 "0 < b \<Longrightarrow> 0 < Fract a b \<longleftrightarrow> 0 < a"
522 by (simp add: Zero_rat_def zero_less_mult_iff)
524 lemma Fract_less_zero_iff:
525 "0 < b \<Longrightarrow> Fract a b < 0 \<longleftrightarrow> a < 0"
526 by (simp add: Zero_rat_def mult_less_0_iff)
528 lemma zero_le_Fract_iff:
529 "0 < b \<Longrightarrow> 0 \<le> Fract a b \<longleftrightarrow> 0 \<le> a"
530 by (simp add: Zero_rat_def zero_le_mult_iff)
532 lemma Fract_le_zero_iff:
533 "0 < b \<Longrightarrow> Fract a b \<le> 0 \<longleftrightarrow> a \<le> 0"
534 by (simp add: Zero_rat_def mult_le_0_iff)
536 lemma one_less_Fract_iff:
537 "0 < b \<Longrightarrow> 1 < Fract a b \<longleftrightarrow> b < a"
538 by (simp add: One_rat_def mult_less_cancel_right_disj)
540 lemma Fract_less_one_iff:
541 "0 < b \<Longrightarrow> Fract a b < 1 \<longleftrightarrow> a < b"
542 by (simp add: One_rat_def mult_less_cancel_right_disj)
544 lemma one_le_Fract_iff:
545 "0 < b \<Longrightarrow> 1 \<le> Fract a b \<longleftrightarrow> b \<le> a"
546 by (simp add: One_rat_def mult_le_cancel_right)
548 lemma Fract_le_one_iff:
549 "0 < b \<Longrightarrow> Fract a b \<le> 1 \<longleftrightarrow> a \<le> b"
550 by (simp add: One_rat_def mult_le_cancel_right)
553 subsubsection {* Rationals are an Archimedean field *}
555 lemma rat_floor_lemma:
557 shows "of_int (a div b) \<le> Fract a b \<and> Fract a b < of_int (a div b + 1)"
559 have "Fract a b = of_int (a div b) + Fract (a mod b) b"
560 using `0 < b` by (simp add: of_int_rat)
561 moreover have "0 \<le> Fract (a mod b) b \<and> Fract (a mod b) b < 1"
562 using `0 < b` by (simp add: zero_le_Fract_iff Fract_less_one_iff)
563 ultimately show ?thesis by simp
566 instance rat :: archimedean_field
569 show "\<exists>z. r \<le> of_int z"
572 then have "Fract a b \<le> of_int (a div b + 1)"
573 using rat_floor_lemma [of b a] by simp
574 then show "\<exists>z. Fract a b \<le> of_int z" ..
579 assumes "0 < b" shows "floor (Fract a b) = a div b"
580 using rat_floor_lemma [OF `0 < b`, of a]
581 by (simp add: floor_unique)
584 subsection {* Linear arithmetic setup *}
587 K (Lin_Arith.add_inj_thms [@{thm of_nat_le_iff} RS iffD2, @{thm of_nat_eq_iff} RS iffD2]
588 (* not needed because x < (y::nat) can be rewritten as Suc x <= y: of_nat_less_iff RS iffD2 *)
589 #> Lin_Arith.add_inj_thms [@{thm of_int_le_iff} RS iffD2, @{thm of_int_eq_iff} RS iffD2]
590 (* not needed because x < (y::int) can be rewritten as x + 1 <= y: of_int_less_iff RS iffD2 *)
591 #> Lin_Arith.add_simps [@{thm neg_less_iff_less},
592 @{thm True_implies_equals},
593 read_instantiate @{context} [(("a", 0), "(number_of ?v)")] @{thm right_distrib},
594 @{thm divide_1}, @{thm divide_zero_left},
595 @{thm times_divide_eq_right}, @{thm times_divide_eq_left},
596 @{thm minus_divide_left} RS sym, @{thm minus_divide_right} RS sym,
597 @{thm of_int_minus}, @{thm of_int_diff},
598 @{thm of_int_of_nat_eq}]
599 #> Lin_Arith.add_simprocs Numeral_Simprocs.field_cancel_numeral_factors
600 #> Lin_Arith.add_inj_const (@{const_name of_nat}, @{typ "nat => rat"})
601 #> Lin_Arith.add_inj_const (@{const_name of_int}, @{typ "int => rat"}))
605 subsection {* Embedding from Rationals to other Fields *}
607 class field_char_0 = field + ring_char_0
609 subclass (in ordered_field) field_char_0 ..
614 definition of_rat :: "rat \<Rightarrow> 'a" where
615 [code del]: "of_rat q = contents (\<Union>(a,b) \<in> Rep_Rat q. {of_int a / of_int b})"
619 lemma of_rat_congruent:
620 "(\<lambda>(a, b). {of_int a / of_int b :: 'a::field_char_0}) respects ratrel"
621 apply (rule congruent.intro)
622 apply (clarsimp simp add: nonzero_divide_eq_eq nonzero_eq_divide_eq)
623 apply (simp only: of_int_mult [symmetric])
626 lemma of_rat_rat: "b \<noteq> 0 \<Longrightarrow> of_rat (Fract a b) = of_int a / of_int b"
627 unfolding Fract_def of_rat_def by (simp add: UN_ratrel of_rat_congruent)
629 lemma of_rat_0 [simp]: "of_rat 0 = 0"
630 by (simp add: Zero_rat_def of_rat_rat)
632 lemma of_rat_1 [simp]: "of_rat 1 = 1"
633 by (simp add: One_rat_def of_rat_rat)
635 lemma of_rat_add: "of_rat (a + b) = of_rat a + of_rat b"
636 by (induct a, induct b, simp add: of_rat_rat add_frac_eq)
638 lemma of_rat_minus: "of_rat (- a) = - of_rat a"
639 by (induct a, simp add: of_rat_rat)
641 lemma of_rat_diff: "of_rat (a - b) = of_rat a - of_rat b"
642 by (simp only: diff_minus of_rat_add of_rat_minus)
644 lemma of_rat_mult: "of_rat (a * b) = of_rat a * of_rat b"
645 apply (induct a, induct b, simp add: of_rat_rat)
646 apply (simp add: divide_inverse nonzero_inverse_mult_distrib mult_ac)
649 lemma nonzero_of_rat_inverse:
650 "a \<noteq> 0 \<Longrightarrow> of_rat (inverse a) = inverse (of_rat a)"
651 apply (rule inverse_unique [symmetric])
652 apply (simp add: of_rat_mult [symmetric])
655 lemma of_rat_inverse:
656 "(of_rat (inverse a)::'a::{field_char_0,division_by_zero}) =
658 by (cases "a = 0", simp_all add: nonzero_of_rat_inverse)
660 lemma nonzero_of_rat_divide:
661 "b \<noteq> 0 \<Longrightarrow> of_rat (a / b) = of_rat a / of_rat b"
662 by (simp add: divide_inverse of_rat_mult nonzero_of_rat_inverse)
665 "(of_rat (a / b)::'a::{field_char_0,division_by_zero})
666 = of_rat a / of_rat b"
667 by (cases "b = 0") (simp_all add: nonzero_of_rat_divide)
670 "(of_rat (a ^ n)::'a::field_char_0) = of_rat a ^ n"
671 by (induct n) (simp_all add: of_rat_mult)
673 lemma of_rat_eq_iff [simp]: "(of_rat a = of_rat b) = (a = b)"
674 apply (induct a, induct b)
675 apply (simp add: of_rat_rat eq_rat)
676 apply (simp add: nonzero_divide_eq_eq nonzero_eq_divide_eq)
677 apply (simp only: of_int_mult [symmetric] of_int_eq_iff)
681 "(of_rat r :: 'a::ordered_field) < of_rat s \<longleftrightarrow> r < s"
682 proof (induct r, induct s)
684 assume not_zero: "b > 0" "d > 0"
685 then have "b * d > 0" by (rule mult_pos_pos)
686 have of_int_divide_less_eq:
687 "(of_int a :: 'a) / of_int b < of_int c / of_int d
688 \<longleftrightarrow> (of_int a :: 'a) * of_int d < of_int c * of_int b"
689 using not_zero by (simp add: pos_less_divide_eq pos_divide_less_eq)
690 show "(of_rat (Fract a b) :: 'a::ordered_field) < of_rat (Fract c d)
691 \<longleftrightarrow> Fract a b < Fract c d"
692 using not_zero `b * d > 0`
693 by (simp add: of_rat_rat of_int_divide_less_eq of_int_mult [symmetric] del: of_int_mult)
696 lemma of_rat_less_eq:
697 "(of_rat r :: 'a::ordered_field) \<le> of_rat s \<longleftrightarrow> r \<le> s"
698 unfolding le_less by (auto simp add: of_rat_less)
700 lemmas of_rat_eq_0_iff [simp] = of_rat_eq_iff [of _ 0, simplified]
702 lemma of_rat_eq_id [simp]: "of_rat = id"
705 show "of_rat a = id a"
707 (simp add: of_rat_rat Fract_of_int_eq [symmetric])
710 text{*Collapse nested embeddings*}
711 lemma of_rat_of_nat_eq [simp]: "of_rat (of_nat n) = of_nat n"
712 by (induct n) (simp_all add: of_rat_add)
714 lemma of_rat_of_int_eq [simp]: "of_rat (of_int z) = of_int z"
715 by (cases z rule: int_diff_cases) (simp add: of_rat_diff)
717 lemma of_rat_number_of_eq [simp]:
718 "of_rat (number_of w) = (number_of w :: 'a::{number_ring,field_char_0})"
719 by (simp add: number_of_eq)
721 lemmas zero_rat = Zero_rat_def
722 lemmas one_rat = One_rat_def
725 rat_of_nat :: "nat \<Rightarrow> rat"
727 "rat_of_nat \<equiv> of_nat"
730 rat_of_int :: "int \<Rightarrow> rat"
732 "rat_of_int \<equiv> of_int"
734 subsection {* The Set of Rational Numbers *}
740 Rats :: "'a set" where
741 [code del]: "Rats = range of_rat"
748 lemma Rats_of_rat [simp]: "of_rat r \<in> Rats"
749 by (simp add: Rats_def)
751 lemma Rats_of_int [simp]: "of_int z \<in> Rats"
752 by (subst of_rat_of_int_eq [symmetric], rule Rats_of_rat)
754 lemma Rats_of_nat [simp]: "of_nat n \<in> Rats"
755 by (subst of_rat_of_nat_eq [symmetric], rule Rats_of_rat)
757 lemma Rats_number_of [simp]:
758 "(number_of w::'a::{number_ring,field_char_0}) \<in> Rats"
759 by (subst of_rat_number_of_eq [symmetric], rule Rats_of_rat)
761 lemma Rats_0 [simp]: "0 \<in> Rats"
762 apply (unfold Rats_def)
763 apply (rule range_eqI)
764 apply (rule of_rat_0 [symmetric])
767 lemma Rats_1 [simp]: "1 \<in> Rats"
768 apply (unfold Rats_def)
769 apply (rule range_eqI)
770 apply (rule of_rat_1 [symmetric])
773 lemma Rats_add [simp]: "\<lbrakk>a \<in> Rats; b \<in> Rats\<rbrakk> \<Longrightarrow> a + b \<in> Rats"
774 apply (auto simp add: Rats_def)
775 apply (rule range_eqI)
776 apply (rule of_rat_add [symmetric])
779 lemma Rats_minus [simp]: "a \<in> Rats \<Longrightarrow> - a \<in> Rats"
780 apply (auto simp add: Rats_def)
781 apply (rule range_eqI)
782 apply (rule of_rat_minus [symmetric])
785 lemma Rats_diff [simp]: "\<lbrakk>a \<in> Rats; b \<in> Rats\<rbrakk> \<Longrightarrow> a - b \<in> Rats"
786 apply (auto simp add: Rats_def)
787 apply (rule range_eqI)
788 apply (rule of_rat_diff [symmetric])
791 lemma Rats_mult [simp]: "\<lbrakk>a \<in> Rats; b \<in> Rats\<rbrakk> \<Longrightarrow> a * b \<in> Rats"
792 apply (auto simp add: Rats_def)
793 apply (rule range_eqI)
794 apply (rule of_rat_mult [symmetric])
797 lemma nonzero_Rats_inverse:
798 fixes a :: "'a::field_char_0"
799 shows "\<lbrakk>a \<in> Rats; a \<noteq> 0\<rbrakk> \<Longrightarrow> inverse a \<in> Rats"
800 apply (auto simp add: Rats_def)
801 apply (rule range_eqI)
802 apply (erule nonzero_of_rat_inverse [symmetric])
805 lemma Rats_inverse [simp]:
806 fixes a :: "'a::{field_char_0,division_by_zero}"
807 shows "a \<in> Rats \<Longrightarrow> inverse a \<in> Rats"
808 apply (auto simp add: Rats_def)
809 apply (rule range_eqI)
810 apply (rule of_rat_inverse [symmetric])
813 lemma nonzero_Rats_divide:
814 fixes a b :: "'a::field_char_0"
815 shows "\<lbrakk>a \<in> Rats; b \<in> Rats; b \<noteq> 0\<rbrakk> \<Longrightarrow> a / b \<in> Rats"
816 apply (auto simp add: Rats_def)
817 apply (rule range_eqI)
818 apply (erule nonzero_of_rat_divide [symmetric])
821 lemma Rats_divide [simp]:
822 fixes a b :: "'a::{field_char_0,division_by_zero}"
823 shows "\<lbrakk>a \<in> Rats; b \<in> Rats\<rbrakk> \<Longrightarrow> a / b \<in> Rats"
824 apply (auto simp add: Rats_def)
825 apply (rule range_eqI)
826 apply (rule of_rat_divide [symmetric])
829 lemma Rats_power [simp]:
830 fixes a :: "'a::field_char_0"
831 shows "a \<in> Rats \<Longrightarrow> a ^ n \<in> Rats"
832 apply (auto simp add: Rats_def)
833 apply (rule range_eqI)
834 apply (rule of_rat_power [symmetric])
837 lemma Rats_cases [cases set: Rats]:
838 assumes "q \<in> \<rat>"
839 obtains (of_rat) r where "q = of_rat r"
842 from `q \<in> \<rat>` have "q \<in> range of_rat" unfolding Rats_def .
843 then obtain r where "q = of_rat r" ..
847 lemma Rats_induct [case_names of_rat, induct set: Rats]:
848 "q \<in> \<rat> \<Longrightarrow> (\<And>r. P (of_rat r)) \<Longrightarrow> P q"
849 by (rule Rats_cases) auto
852 subsection {* Implementation of rational numbers as pairs of integers *}
854 lemma Fract_norm: "Fract (a div zgcd a b) (b div zgcd a b) = Fract a b"
855 proof (cases "a = 0 \<or> b = 0")
856 case True then show ?thesis by (auto simp add: eq_rat)
859 case False then have "a \<noteq> 0" and "b \<noteq> 0" by auto
860 then have "?c \<noteq> 0" by simp
861 then have "Fract ?c ?c = Fract 1 1" by (simp add: eq_rat)
862 moreover have "Fract (a div ?c * ?c + a mod ?c) (b div ?c * ?c + b mod ?c) = Fract a b"
863 by (simp add: semiring_div_class.mod_div_equality)
864 moreover have "a mod ?c = 0" by (simp add: dvd_eq_mod_eq_0 [symmetric])
865 moreover have "b mod ?c = 0" by (simp add: dvd_eq_mod_eq_0 [symmetric])
866 ultimately show ?thesis
867 by (simp add: mult_rat [symmetric])
870 definition Fract_norm :: "int \<Rightarrow> int \<Rightarrow> rat" where
871 [simp, code del]: "Fract_norm a b = Fract a b"
873 lemma Fract_norm_code [code]: "Fract_norm a b = (if a = 0 \<or> b = 0 then 0 else let c = zgcd a b in
874 if b > 0 then Fract (a div c) (b div c) else Fract (- (a div c)) (- (b div c)))"
875 by (simp add: eq_rat Zero_rat_def Let_def Fract_norm)
878 "of_rat (Fract a b) = (if b \<noteq> 0 then of_int a / of_int b else 0)"
879 by (cases "b = 0") (simp_all add: rat_number_collapse of_rat_rat)
881 instantiation rat :: eq
884 definition [code del]: "eq_class.eq (a\<Colon>rat) b \<longleftrightarrow> a - b = 0"
886 instance by default (simp add: eq_rat_def)
888 lemma rat_eq_code [code]:
889 "eq_class.eq (Fract a b) (Fract c d) \<longleftrightarrow> (if b = 0
890 then c = 0 \<or> d = 0
892 then a = 0 \<or> b = 0
894 by (auto simp add: eq eq_rat)
896 lemma rat_eq_refl [code nbe]:
897 "eq_class.eq (r::rat) r \<longleftrightarrow> True"
898 by (rule HOL.eq_refl)
903 assumes "b \<noteq> 0"
905 shows "Fract a b \<le> Fract c d \<longleftrightarrow> a * \<bar>d\<bar> * sgn b \<le> c * \<bar>b\<bar> * sgn d"
907 have abs_sgn: "\<And>k::int. \<bar>k\<bar> = k * sgn k" unfolding abs_if sgn_if by simp
908 have "a * d * (b * d) \<le> c * b * (b * d) \<longleftrightarrow> a * d * (sgn b * sgn d) \<le> c * b * (sgn b * sgn d)"
909 proof (cases "b * d > 0")
911 moreover from True have "sgn b * sgn d = 1"
912 by (simp add: sgn_times [symmetric] sgn_1_pos)
913 ultimately show ?thesis by (simp add: mult_le_cancel_right)
915 case False with assms have "b * d < 0" by (simp add: less_le)
916 moreover from this have "sgn b * sgn d = - 1"
917 by (simp only: sgn_times [symmetric] sgn_1_neg)
918 ultimately show ?thesis by (simp add: mult_le_cancel_right)
920 also have "\<dots> \<longleftrightarrow> a * \<bar>d\<bar> * sgn b \<le> c * \<bar>b\<bar> * sgn d"
921 by (simp add: abs_sgn mult_ac)
922 finally show ?thesis using assms by simp
926 assumes "b \<noteq> 0"
928 shows "Fract a b < Fract c d \<longleftrightarrow> a * \<bar>d\<bar> * sgn b < c * \<bar>b\<bar> * sgn d"
930 have abs_sgn: "\<And>k::int. \<bar>k\<bar> = k * sgn k" unfolding abs_if sgn_if by simp
931 have "a * d * (b * d) < c * b * (b * d) \<longleftrightarrow> a * d * (sgn b * sgn d) < c * b * (sgn b * sgn d)"
932 proof (cases "b * d > 0")
934 moreover from True have "sgn b * sgn d = 1"
935 by (simp add: sgn_times [symmetric] sgn_1_pos)
936 ultimately show ?thesis by (simp add: mult_less_cancel_right)
938 case False with assms have "b * d < 0" by (simp add: less_le)
939 moreover from this have "sgn b * sgn d = - 1"
940 by (simp only: sgn_times [symmetric] sgn_1_neg)
941 ultimately show ?thesis by (simp add: mult_less_cancel_right)
943 also have "\<dots> \<longleftrightarrow> a * \<bar>d\<bar> * sgn b < c * \<bar>b\<bar> * sgn d"
944 by (simp add: abs_sgn mult_ac)
945 finally show ?thesis using assms by simp
948 lemma (in ordered_idom) sgn_greater [simp]:
949 "0 < sgn a \<longleftrightarrow> 0 < a"
950 unfolding sgn_if by auto
952 lemma (in ordered_idom) sgn_less [simp]:
953 "sgn a < 0 \<longleftrightarrow> a < 0"
954 unfolding sgn_if by auto
956 lemma rat_le_eq_code [code]:
957 "Fract a b < Fract c d \<longleftrightarrow> (if b = 0
958 then sgn c * sgn d > 0
960 then sgn a * sgn b < 0
961 else a * \<bar>d\<bar> * sgn b < c * \<bar>b\<bar> * sgn d)"
962 by (auto simp add: sgn_times mult_less_0_iff zero_less_mult_iff less_rat' eq_rat simp del: less_rat)
964 lemma rat_less_eq_code [code]:
965 "Fract a b \<le> Fract c d \<longleftrightarrow> (if b = 0
966 then sgn c * sgn d \<ge> 0
968 then sgn a * sgn b \<le> 0
969 else a * \<bar>d\<bar> * sgn b \<le> c * \<bar>b\<bar> * sgn d)"
970 by (auto simp add: sgn_times mult_le_0_iff zero_le_mult_iff le_rat' eq_rat simp del: le_rat)
971 (auto simp add: le_less not_less sgn_0_0)
974 lemma rat_plus_code [code]:
975 "Fract a b + Fract c d = (if b = 0
979 else Fract_norm (a * d + c * b) (b * d))"
980 by (simp add: eq_rat, simp add: Zero_rat_def)
982 lemma rat_times_code [code]:
983 "Fract a b * Fract c d = Fract_norm (a * c) (b * d)"
986 lemma rat_minus_code [code]:
987 "Fract a b - Fract c d = (if b = 0
991 else Fract_norm (a * d - c * b) (b * d))"
992 by (simp add: eq_rat, simp add: Zero_rat_def)
994 lemma rat_inverse_code [code]:
995 "inverse (Fract a b) = (if b = 0 then Fract 1 0
996 else if a < 0 then Fract (- b) (- a)
998 by (simp add: eq_rat)
1000 lemma rat_divide_code [code]:
1001 "Fract a b / Fract c d = Fract_norm (a * d) (b * c)"
1004 definition (in term_syntax)
1005 valterm_fract :: "int \<times> (unit \<Rightarrow> Code_Eval.term) \<Rightarrow> int \<times> (unit \<Rightarrow> Code_Eval.term) \<Rightarrow> rat \<times> (unit \<Rightarrow> Code_Eval.term)" where
1006 [code inline]: "valterm_fract k l = Code_Eval.valtermify Fract {\<cdot>} k {\<cdot>} l"
1008 notation fcomp (infixl "o>" 60)
1009 notation scomp (infixl "o\<rightarrow>" 60)
1011 instantiation rat :: random
1015 "random i = random i o\<rightarrow> (\<lambda>num. Random.range i o\<rightarrow> (\<lambda>denom. Pair (
1016 let j = Code_Index.int_of (denom + 1)
1017 in valterm_fract num (j, \<lambda>u. Code_Eval.term_of j))))"
1023 no_notation fcomp (infixl "o>" 60)
1024 no_notation scomp (infixl "o\<rightarrow>" 60)
1026 hide (open) const Fract_norm
1028 text {* Setup for SML code generator *}
1031 rat ("(int */ int)")
1033 fun term_of_rat (p, q) =
1035 val rT = Type ("Rational.rat", [])
1037 if q = 1 orelse p = 0 then HOLogic.mk_number rT p
1038 else @{term "op / \<Colon> rat \<Rightarrow> rat \<Rightarrow> rat"} $
1039 HOLogic.mk_number rT p $ HOLogic.mk_number rT q
1045 val p = random_range 0 i;
1046 val q = random_range 1 (i + 1);
1047 val g = Integer.gcd p q;
1050 val r = (if one_of [true, false] then p' else ~ p',
1051 if p' = 0 then 0 else q')
1053 (r, fn () => term_of_rat r)
1061 "of_int :: int \<Rightarrow> rat" ("\<module>rat'_of'_int")
1063 fun rat_of_int 0 = (0, 0)
1064 | rat_of_int i = (i, 1);