src/HOL/Rat.thy
 author haftmann Sun Sep 21 16:56:11 2014 +0200 (2014-09-21) changeset 58410 6d46ad54a2ab parent 57576 083dfad2727c child 58834 773b378d9313 permissions -rw-r--r--
explicit separation of signed and unsigned numerals using existing lexical categories num and xnum
```     1 (*  Title:  HOL/Rat.thy
```
```     2     Author: Markus Wenzel, TU Muenchen
```
```     3 *)
```
```     4
```
```     5 header {* Rational numbers *}
```
```     6
```
```     7 theory Rat
```
```     8 imports GCD Archimedean_Field
```
```     9 begin
```
```    10
```
```    11 subsection {* Rational numbers as quotient *}
```
```    12
```
```    13 subsubsection {* Construction of the type of rational numbers *}
```
```    14
```
```    15 definition
```
```    16   ratrel :: "(int \<times> int) \<Rightarrow> (int \<times> int) \<Rightarrow> bool" where
```
```    17   "ratrel = (\<lambda>x y. snd x \<noteq> 0 \<and> snd y \<noteq> 0 \<and> fst x * snd y = fst y * snd x)"
```
```    18
```
```    19 lemma ratrel_iff [simp]:
```
```    20   "ratrel x y \<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)
```
```    22
```
```    23 lemma exists_ratrel_refl: "\<exists>x. ratrel x x"
```
```    24   by (auto intro!: one_neq_zero)
```
```    25
```
```    26 lemma symp_ratrel: "symp ratrel"
```
```    27   by (simp add: ratrel_def symp_def)
```
```    28
```
```    29 lemma transp_ratrel: "transp ratrel"
```
```    30 proof (rule transpI, unfold split_paired_all)
```
```    31   fix a b a' b' a'' b'' :: int
```
```    32   assume A: "ratrel (a, b) (a', b')"
```
```    33   assume B: "ratrel (a', b') (a'', b'')"
```
```    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 "ratrel (a, b) (a'', b'')" by auto
```
```    43 qed
```
```    44
```
```    45 lemma part_equivp_ratrel: "part_equivp ratrel"
```
```    46   by (rule part_equivpI [OF exists_ratrel_refl symp_ratrel transp_ratrel])
```
```    47
```
```    48 quotient_type rat = "int \<times> int" / partial: "ratrel"
```
```    49   morphisms Rep_Rat Abs_Rat
```
```    50   by (rule part_equivp_ratrel)
```
```    51
```
```    52 lemma Domainp_cr_rat [transfer_domain_rule]: "Domainp pcr_rat = (\<lambda>x. snd x \<noteq> 0)"
```
```    53 by (simp add: rat.domain_eq)
```
```    54
```
```    55 subsubsection {* Representation and basic operations *}
```
```    56
```
```    57 lift_definition Fract :: "int \<Rightarrow> int \<Rightarrow> rat"
```
```    58   is "\<lambda>a b. if b = 0 then (0, 1) else (a, b)"
```
```    59   by simp
```
```    60
```
```    61 lemma eq_rat:
```
```    62   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"
```
```    63   and "\<And>a. Fract a 0 = Fract 0 1"
```
```    64   and "\<And>a c. Fract 0 a = Fract 0 c"
```
```    65   by (transfer, simp)+
```
```    66
```
```    67 lemma Rat_cases [case_names Fract, cases type: rat]:
```
```    68   assumes "\<And>a b. q = Fract a b \<Longrightarrow> b > 0 \<Longrightarrow> coprime a b \<Longrightarrow> C"
```
```    69   shows C
```
```    70 proof -
```
```    71   obtain a b :: int where "q = Fract a b" and "b \<noteq> 0"
```
```    72     by transfer simp
```
```    73   let ?a = "a div gcd a b"
```
```    74   let ?b = "b div gcd a b"
```
```    75   from `b \<noteq> 0` have "?b * gcd a b = b"
```
```    76     by (simp add: dvd_div_mult_self)
```
```    77   with `b \<noteq> 0` have "?b \<noteq> 0" by auto
```
```    78   from `q = Fract a b` `b \<noteq> 0` `?b \<noteq> 0` have q: "q = Fract ?a ?b"
```
```    79     by (simp add: eq_rat dvd_div_mult mult.commute [of a])
```
```    80   from `b \<noteq> 0` have coprime: "coprime ?a ?b"
```
```    81     by (auto intro: div_gcd_coprime_int)
```
```    82   show C proof (cases "b > 0")
```
```    83     case True
```
```    84     note assms
```
```    85     moreover note q
```
```    86     moreover from True have "?b > 0" by (simp add: nonneg1_imp_zdiv_pos_iff)
```
```    87     moreover note coprime
```
```    88     ultimately show C .
```
```    89   next
```
```    90     case False
```
```    91     note assms
```
```    92     moreover have "q = Fract (- ?a) (- ?b)" unfolding q by transfer simp
```
```    93     moreover from False `b \<noteq> 0` have "- ?b > 0" by (simp add: pos_imp_zdiv_neg_iff)
```
```    94     moreover from coprime have "coprime (- ?a) (- ?b)" by simp
```
```    95     ultimately show C .
```
```    96   qed
```
```    97 qed
```
```    98
```
```    99 lemma Rat_induct [case_names Fract, induct type: rat]:
```
```   100   assumes "\<And>a b. b > 0 \<Longrightarrow> coprime a b \<Longrightarrow> P (Fract a b)"
```
```   101   shows "P q"
```
```   102   using assms by (cases q) simp
```
```   103
```
```   104 instantiation rat :: field_inverse_zero
```
```   105 begin
```
```   106
```
```   107 lift_definition zero_rat :: "rat" is "(0, 1)"
```
```   108   by simp
```
```   109
```
```   110 lift_definition one_rat :: "rat" is "(1, 1)"
```
```   111   by simp
```
```   112
```
```   113 lemma Zero_rat_def: "0 = Fract 0 1"
```
```   114   by transfer simp
```
```   115
```
```   116 lemma One_rat_def: "1 = Fract 1 1"
```
```   117   by transfer simp
```
```   118
```
```   119 lift_definition plus_rat :: "rat \<Rightarrow> rat \<Rightarrow> rat"
```
```   120   is "\<lambda>x y. (fst x * snd y + fst y * snd x, snd x * snd y)"
```
```   121   by (clarsimp, simp add: distrib_right, simp add: ac_simps)
```
```   122
```
```   123 lemma add_rat [simp]:
```
```   124   assumes "b \<noteq> 0" and "d \<noteq> 0"
```
```   125   shows "Fract a b + Fract c d = Fract (a * d + c * b) (b * d)"
```
```   126   using assms by transfer simp
```
```   127
```
```   128 lift_definition uminus_rat :: "rat \<Rightarrow> rat" is "\<lambda>x. (- fst x, snd x)"
```
```   129   by simp
```
```   130
```
```   131 lemma minus_rat [simp]: "- Fract a b = Fract (- a) b"
```
```   132   by transfer simp
```
```   133
```
```   134 lemma minus_rat_cancel [simp]: "Fract (- a) (- b) = Fract a b"
```
```   135   by (cases "b = 0") (simp_all add: eq_rat)
```
```   136
```
```   137 definition
```
```   138   diff_rat_def: "q - r = q + - (r::rat)"
```
```   139
```
```   140 lemma diff_rat [simp]:
```
```   141   assumes "b \<noteq> 0" and "d \<noteq> 0"
```
```   142   shows "Fract a b - Fract c d = Fract (a * d - c * b) (b * d)"
```
```   143   using assms by (simp add: diff_rat_def)
```
```   144
```
```   145 lift_definition times_rat :: "rat \<Rightarrow> rat \<Rightarrow> rat"
```
```   146   is "\<lambda>x y. (fst x * fst y, snd x * snd y)"
```
```   147   by (simp add: ac_simps)
```
```   148
```
```   149 lemma mult_rat [simp]: "Fract a b * Fract c d = Fract (a * c) (b * d)"
```
```   150   by transfer simp
```
```   151
```
```   152 lemma mult_rat_cancel:
```
```   153   assumes "c \<noteq> 0"
```
```   154   shows "Fract (c * a) (c * b) = Fract a b"
```
```   155   using assms by transfer simp
```
```   156
```
```   157 lift_definition inverse_rat :: "rat \<Rightarrow> rat"
```
```   158   is "\<lambda>x. if fst x = 0 then (0, 1) else (snd x, fst x)"
```
```   159   by (auto simp add: mult.commute)
```
```   160
```
```   161 lemma inverse_rat [simp]: "inverse (Fract a b) = Fract b a"
```
```   162   by transfer simp
```
```   163
```
```   164 definition
```
```   165   divide_rat_def: "q / r = q * inverse (r::rat)"
```
```   166
```
```   167 lemma divide_rat [simp]: "Fract a b / Fract c d = Fract (a * d) (b * c)"
```
```   168   by (simp add: divide_rat_def)
```
```   169
```
```   170 instance proof
```
```   171   fix q r s :: rat
```
```   172   show "(q * r) * s = q * (r * s)"
```
```   173     by transfer simp
```
```   174   show "q * r = r * q"
```
```   175     by transfer simp
```
```   176   show "1 * q = q"
```
```   177     by transfer simp
```
```   178   show "(q + r) + s = q + (r + s)"
```
```   179     by transfer (simp add: algebra_simps)
```
```   180   show "q + r = r + q"
```
```   181     by transfer simp
```
```   182   show "0 + q = q"
```
```   183     by transfer simp
```
```   184   show "- q + q = 0"
```
```   185     by transfer simp
```
```   186   show "q - r = q + - r"
```
```   187     by (fact diff_rat_def)
```
```   188   show "(q + r) * s = q * s + r * s"
```
```   189     by transfer (simp add: algebra_simps)
```
```   190   show "(0::rat) \<noteq> 1"
```
```   191     by transfer simp
```
```   192   { assume "q \<noteq> 0" thus "inverse q * q = 1"
```
```   193     by transfer simp }
```
```   194   show "q / r = q * inverse r"
```
```   195     by (fact divide_rat_def)
```
```   196   show "inverse 0 = (0::rat)"
```
```   197     by transfer simp
```
```   198 qed
```
```   199
```
```   200 end
```
```   201
```
```   202 lemma of_nat_rat: "of_nat k = Fract (of_nat k) 1"
```
```   203   by (induct k) (simp_all add: Zero_rat_def One_rat_def)
```
```   204
```
```   205 lemma of_int_rat: "of_int k = Fract k 1"
```
```   206   by (cases k rule: int_diff_cases) (simp add: of_nat_rat)
```
```   207
```
```   208 lemma Fract_of_nat_eq: "Fract (of_nat k) 1 = of_nat k"
```
```   209   by (rule of_nat_rat [symmetric])
```
```   210
```
```   211 lemma Fract_of_int_eq: "Fract k 1 = of_int k"
```
```   212   by (rule of_int_rat [symmetric])
```
```   213
```
```   214 lemma rat_number_collapse:
```
```   215   "Fract 0 k = 0"
```
```   216   "Fract 1 1 = 1"
```
```   217   "Fract (numeral w) 1 = numeral w"
```
```   218   "Fract (- numeral w) 1 = - numeral w"
```
```   219   "Fract (- 1) 1 = - 1"
```
```   220   "Fract k 0 = 0"
```
```   221   using Fract_of_int_eq [of "numeral w"]
```
```   222   using Fract_of_int_eq [of "- numeral w"]
```
```   223   by (simp_all add: Zero_rat_def One_rat_def eq_rat)
```
```   224
```
```   225 lemma rat_number_expand:
```
```   226   "0 = Fract 0 1"
```
```   227   "1 = Fract 1 1"
```
```   228   "numeral k = Fract (numeral k) 1"
```
```   229   "- 1 = Fract (- 1) 1"
```
```   230   "- numeral k = Fract (- numeral k) 1"
```
```   231   by (simp_all add: rat_number_collapse)
```
```   232
```
```   233 lemma Rat_cases_nonzero [case_names Fract 0]:
```
```   234   assumes Fract: "\<And>a b. q = Fract a b \<Longrightarrow> b > 0 \<Longrightarrow> a \<noteq> 0 \<Longrightarrow> coprime a b \<Longrightarrow> C"
```
```   235   assumes 0: "q = 0 \<Longrightarrow> C"
```
```   236   shows C
```
```   237 proof (cases "q = 0")
```
```   238   case True then show C using 0 by auto
```
```   239 next
```
```   240   case False
```
```   241   then obtain a b where "q = Fract a b" and "b > 0" and "coprime a b" by (cases q) auto
```
```   242   with False have "0 \<noteq> Fract a b" by simp
```
```   243   with `b > 0` have "a \<noteq> 0" by (simp add: Zero_rat_def eq_rat)
```
```   244   with Fract `q = Fract a b` `b > 0` `coprime a b` show C by blast
```
```   245 qed
```
```   246
```
```   247 subsubsection {* Function @{text normalize} *}
```
```   248
```
```   249 lemma Fract_coprime: "Fract (a div gcd a b) (b div gcd a b) = Fract a b"
```
```   250 proof (cases "b = 0")
```
```   251   case True then show ?thesis by (simp add: eq_rat)
```
```   252 next
```
```   253   case False
```
```   254   moreover have "b div gcd a b * gcd a b = b"
```
```   255     by (rule dvd_div_mult_self) simp
```
```   256   ultimately have "b div gcd a b \<noteq> 0" by auto
```
```   257   with False show ?thesis by (simp add: eq_rat dvd_div_mult mult.commute [of a])
```
```   258 qed
```
```   259
```
```   260 definition normalize :: "int \<times> int \<Rightarrow> int \<times> int" where
```
```   261   "normalize p = (if snd p > 0 then (let a = gcd (fst p) (snd p) in (fst p div a, snd p div a))
```
```   262     else if snd p = 0 then (0, 1)
```
```   263     else (let a = - gcd (fst p) (snd p) in (fst p div a, snd p div a)))"
```
```   264
```
```   265 lemma normalize_crossproduct:
```
```   266   assumes "q \<noteq> 0" "s \<noteq> 0"
```
```   267   assumes "normalize (p, q) = normalize (r, s)"
```
```   268   shows "p * s = r * q"
```
```   269 proof -
```
```   270   have aux: "p * gcd r s = sgn (q * s) * r * gcd p q \<Longrightarrow> q * gcd r s = sgn (q * s) * s * gcd p q \<Longrightarrow> p * s = q * r"
```
```   271   proof -
```
```   272     assume "p * gcd r s = sgn (q * s) * r * gcd p q" and "q * gcd r s = sgn (q * s) * s * gcd p q"
```
```   273     then have "(p * gcd r s) * (sgn (q * s) * s * gcd p q) = (q * gcd r s) * (sgn (q * s) * r * gcd p q)" by simp
```
```   274     with assms show "p * s = q * r" by (auto simp add: ac_simps sgn_times sgn_0_0)
```
```   275   qed
```
```   276   from assms show ?thesis
```
```   277     by (auto simp add: normalize_def Let_def dvd_div_div_eq_mult mult.commute sgn_times split: if_splits intro: aux)
```
```   278 qed
```
```   279
```
```   280 lemma normalize_eq: "normalize (a, b) = (p, q) \<Longrightarrow> Fract p q = Fract a b"
```
```   281   by (auto simp add: normalize_def Let_def Fract_coprime dvd_div_neg rat_number_collapse
```
```   282     split:split_if_asm)
```
```   283
```
```   284 lemma normalize_denom_pos: "normalize r = (p, q) \<Longrightarrow> q > 0"
```
```   285   by (auto simp add: normalize_def Let_def dvd_div_neg pos_imp_zdiv_neg_iff nonneg1_imp_zdiv_pos_iff
```
```   286     split:split_if_asm)
```
```   287
```
```   288 lemma normalize_coprime: "normalize r = (p, q) \<Longrightarrow> coprime p q"
```
```   289   by (auto simp add: normalize_def Let_def dvd_div_neg div_gcd_coprime_int
```
```   290     split:split_if_asm)
```
```   291
```
```   292 lemma normalize_stable [simp]:
```
```   293   "q > 0 \<Longrightarrow> coprime p q \<Longrightarrow> normalize (p, q) = (p, q)"
```
```   294   by (simp add: normalize_def)
```
```   295
```
```   296 lemma normalize_denom_zero [simp]:
```
```   297   "normalize (p, 0) = (0, 1)"
```
```   298   by (simp add: normalize_def)
```
```   299
```
```   300 lemma normalize_negative [simp]:
```
```   301   "q < 0 \<Longrightarrow> normalize (p, q) = normalize (- p, - q)"
```
```   302   by (simp add: normalize_def Let_def dvd_div_neg dvd_neg_div)
```
```   303
```
```   304 text{*
```
```   305   Decompose a fraction into normalized, i.e. coprime numerator and denominator:
```
```   306 *}
```
```   307
```
```   308 definition quotient_of :: "rat \<Rightarrow> int \<times> int" where
```
```   309   "quotient_of x = (THE pair. x = Fract (fst pair) (snd pair) &
```
```   310                    snd pair > 0 & coprime (fst pair) (snd pair))"
```
```   311
```
```   312 lemma quotient_of_unique:
```
```   313   "\<exists>!p. r = Fract (fst p) (snd p) \<and> snd p > 0 \<and> coprime (fst p) (snd p)"
```
```   314 proof (cases r)
```
```   315   case (Fract a b)
```
```   316   then have "r = Fract (fst (a, b)) (snd (a, b)) \<and> snd (a, b) > 0 \<and> coprime (fst (a, b)) (snd (a, b))" by auto
```
```   317   then show ?thesis proof (rule ex1I)
```
```   318     fix p
```
```   319     obtain c d :: int where p: "p = (c, d)" by (cases p)
```
```   320     assume "r = Fract (fst p) (snd p) \<and> snd p > 0 \<and> coprime (fst p) (snd p)"
```
```   321     with p have Fract': "r = Fract c d" "d > 0" "coprime c d" by simp_all
```
```   322     have "c = a \<and> d = b"
```
```   323     proof (cases "a = 0")
```
```   324       case True with Fract Fract' show ?thesis by (simp add: eq_rat)
```
```   325     next
```
```   326       case False
```
```   327       with Fract Fract' have *: "c * b = a * d" and "c \<noteq> 0" by (auto simp add: eq_rat)
```
```   328       then have "c * b > 0 \<longleftrightarrow> a * d > 0" by auto
```
```   329       with `b > 0` `d > 0` have "a > 0 \<longleftrightarrow> c > 0" by (simp add: zero_less_mult_iff)
```
```   330       with `a \<noteq> 0` `c \<noteq> 0` have sgn: "sgn a = sgn c" by (auto simp add: not_less)
```
```   331       from `coprime a b` `coprime c d` have "\<bar>a\<bar> * \<bar>d\<bar> = \<bar>c\<bar> * \<bar>b\<bar> \<longleftrightarrow> \<bar>a\<bar> = \<bar>c\<bar> \<and> \<bar>d\<bar> = \<bar>b\<bar>"
```
```   332         by (simp add: coprime_crossproduct_int)
```
```   333       with `b > 0` `d > 0` have "\<bar>a\<bar> * d = \<bar>c\<bar> * b \<longleftrightarrow> \<bar>a\<bar> = \<bar>c\<bar> \<and> d = b" by simp
```
```   334       then have "a * sgn a * d = c * sgn c * b \<longleftrightarrow> a * sgn a = c * sgn c \<and> d = b" by (simp add: abs_sgn)
```
```   335       with sgn * show ?thesis by (auto simp add: sgn_0_0)
```
```   336     qed
```
```   337     with p show "p = (a, b)" by simp
```
```   338   qed
```
```   339 qed
```
```   340
```
```   341 lemma quotient_of_Fract [code]:
```
```   342   "quotient_of (Fract a b) = normalize (a, b)"
```
```   343 proof -
```
```   344   have "Fract a b = Fract (fst (normalize (a, b))) (snd (normalize (a, b)))" (is ?Fract)
```
```   345     by (rule sym) (auto intro: normalize_eq)
```
```   346   moreover have "0 < snd (normalize (a, b))" (is ?denom_pos)
```
```   347     by (cases "normalize (a, b)") (rule normalize_denom_pos, simp)
```
```   348   moreover have "coprime (fst (normalize (a, b))) (snd (normalize (a, b)))" (is ?coprime)
```
```   349     by (rule normalize_coprime) simp
```
```   350   ultimately have "?Fract \<and> ?denom_pos \<and> ?coprime" by blast
```
```   351   with quotient_of_unique have
```
```   352     "(THE p. Fract a b = Fract (fst p) (snd p) \<and> 0 < snd p \<and> coprime (fst p) (snd p)) = normalize (a, b)"
```
```   353     by (rule the1_equality)
```
```   354   then show ?thesis by (simp add: quotient_of_def)
```
```   355 qed
```
```   356
```
```   357 lemma quotient_of_number [simp]:
```
```   358   "quotient_of 0 = (0, 1)"
```
```   359   "quotient_of 1 = (1, 1)"
```
```   360   "quotient_of (numeral k) = (numeral k, 1)"
```
```   361   "quotient_of (- 1) = (- 1, 1)"
```
```   362   "quotient_of (- numeral k) = (- numeral k, 1)"
```
```   363   by (simp_all add: rat_number_expand quotient_of_Fract)
```
```   364
```
```   365 lemma quotient_of_eq: "quotient_of (Fract a b) = (p, q) \<Longrightarrow> Fract p q = Fract a b"
```
```   366   by (simp add: quotient_of_Fract normalize_eq)
```
```   367
```
```   368 lemma quotient_of_denom_pos: "quotient_of r = (p, q) \<Longrightarrow> q > 0"
```
```   369   by (cases r) (simp add: quotient_of_Fract normalize_denom_pos)
```
```   370
```
```   371 lemma quotient_of_coprime: "quotient_of r = (p, q) \<Longrightarrow> coprime p q"
```
```   372   by (cases r) (simp add: quotient_of_Fract normalize_coprime)
```
```   373
```
```   374 lemma quotient_of_inject:
```
```   375   assumes "quotient_of a = quotient_of b"
```
```   376   shows "a = b"
```
```   377 proof -
```
```   378   obtain p q r s where a: "a = Fract p q"
```
```   379     and b: "b = Fract r s"
```
```   380     and "q > 0" and "s > 0" by (cases a, cases b)
```
```   381   with assms show ?thesis by (simp add: eq_rat quotient_of_Fract normalize_crossproduct)
```
```   382 qed
```
```   383
```
```   384 lemma quotient_of_inject_eq:
```
```   385   "quotient_of a = quotient_of b \<longleftrightarrow> a = b"
```
```   386   by (auto simp add: quotient_of_inject)
```
```   387
```
```   388
```
```   389 subsubsection {* Various *}
```
```   390
```
```   391 lemma Fract_of_int_quotient: "Fract k l = of_int k / of_int l"
```
```   392   by (simp add: Fract_of_int_eq [symmetric])
```
```   393
```
```   394 lemma Fract_add_one: "n \<noteq> 0 ==> Fract (m + n) n = Fract m n + 1"
```
```   395   by (simp add: rat_number_expand)
```
```   396
```
```   397 lemma quotient_of_div:
```
```   398   assumes r: "quotient_of r = (n,d)"
```
```   399   shows "r = of_int n / of_int d"
```
```   400 proof -
```
```   401   from theI'[OF quotient_of_unique[of r], unfolded r[unfolded quotient_of_def]]
```
```   402   have "r = Fract n d" by simp
```
```   403   thus ?thesis using Fract_of_int_quotient by simp
```
```   404 qed
```
```   405
```
```   406 subsubsection {* The ordered field of rational numbers *}
```
```   407
```
```   408 lift_definition positive :: "rat \<Rightarrow> bool"
```
```   409   is "\<lambda>x. 0 < fst x * snd x"
```
```   410 proof (clarsimp)
```
```   411   fix a b c d :: int
```
```   412   assume "b \<noteq> 0" and "d \<noteq> 0" and "a * d = c * b"
```
```   413   hence "a * d * b * d = c * b * b * d"
```
```   414     by simp
```
```   415   hence "a * b * d\<^sup>2 = c * d * b\<^sup>2"
```
```   416     unfolding power2_eq_square by (simp add: ac_simps)
```
```   417   hence "0 < a * b * d\<^sup>2 \<longleftrightarrow> 0 < c * d * b\<^sup>2"
```
```   418     by simp
```
```   419   thus "0 < a * b \<longleftrightarrow> 0 < c * d"
```
```   420     using `b \<noteq> 0` and `d \<noteq> 0`
```
```   421     by (simp add: zero_less_mult_iff)
```
```   422 qed
```
```   423
```
```   424 lemma positive_zero: "\<not> positive 0"
```
```   425   by transfer simp
```
```   426
```
```   427 lemma positive_add:
```
```   428   "positive x \<Longrightarrow> positive y \<Longrightarrow> positive (x + y)"
```
```   429 apply transfer
```
```   430 apply (simp add: zero_less_mult_iff)
```
```   431 apply (elim disjE, simp_all add: add_pos_pos add_neg_neg
```
```   432   mult_pos_neg mult_neg_pos mult_neg_neg)
```
```   433 done
```
```   434
```
```   435 lemma positive_mult:
```
```   436   "positive x \<Longrightarrow> positive y \<Longrightarrow> positive (x * y)"
```
```   437 by transfer (drule (1) mult_pos_pos, simp add: ac_simps)
```
```   438
```
```   439 lemma positive_minus:
```
```   440   "\<not> positive x \<Longrightarrow> x \<noteq> 0 \<Longrightarrow> positive (- x)"
```
```   441 by transfer (force simp: neq_iff zero_less_mult_iff mult_less_0_iff)
```
```   442
```
```   443 instantiation rat :: linordered_field_inverse_zero
```
```   444 begin
```
```   445
```
```   446 definition
```
```   447   "x < y \<longleftrightarrow> positive (y - x)"
```
```   448
```
```   449 definition
```
```   450   "x \<le> (y::rat) \<longleftrightarrow> x < y \<or> x = y"
```
```   451
```
```   452 definition
```
```   453   "abs (a::rat) = (if a < 0 then - a else a)"
```
```   454
```
```   455 definition
```
```   456   "sgn (a::rat) = (if a = 0 then 0 else if 0 < a then 1 else - 1)"
```
```   457
```
```   458 instance proof
```
```   459   fix a b c :: rat
```
```   460   show "\<bar>a\<bar> = (if a < 0 then - a else a)"
```
```   461     by (rule abs_rat_def)
```
```   462   show "a < b \<longleftrightarrow> a \<le> b \<and> \<not> b \<le> a"
```
```   463     unfolding less_eq_rat_def less_rat_def
```
```   464     by (auto, drule (1) positive_add, simp_all add: positive_zero)
```
```   465   show "a \<le> a"
```
```   466     unfolding less_eq_rat_def by simp
```
```   467   show "a \<le> b \<Longrightarrow> b \<le> c \<Longrightarrow> a \<le> c"
```
```   468     unfolding less_eq_rat_def less_rat_def
```
```   469     by (auto, drule (1) positive_add, simp add: algebra_simps)
```
```   470   show "a \<le> b \<Longrightarrow> b \<le> a \<Longrightarrow> a = b"
```
```   471     unfolding less_eq_rat_def less_rat_def
```
```   472     by (auto, drule (1) positive_add, simp add: positive_zero)
```
```   473   show "a \<le> b \<Longrightarrow> c + a \<le> c + b"
```
```   474     unfolding less_eq_rat_def less_rat_def by auto
```
```   475   show "sgn a = (if a = 0 then 0 else if 0 < a then 1 else - 1)"
```
```   476     by (rule sgn_rat_def)
```
```   477   show "a \<le> b \<or> b \<le> a"
```
```   478     unfolding less_eq_rat_def less_rat_def
```
```   479     by (auto dest!: positive_minus)
```
```   480   show "a < b \<Longrightarrow> 0 < c \<Longrightarrow> c * a < c * b"
```
```   481     unfolding less_rat_def
```
```   482     by (drule (1) positive_mult, simp add: algebra_simps)
```
```   483 qed
```
```   484
```
```   485 end
```
```   486
```
```   487 instantiation rat :: distrib_lattice
```
```   488 begin
```
```   489
```
```   490 definition
```
```   491   "(inf :: rat \<Rightarrow> rat \<Rightarrow> rat) = min"
```
```   492
```
```   493 definition
```
```   494   "(sup :: rat \<Rightarrow> rat \<Rightarrow> rat) = max"
```
```   495
```
```   496 instance proof
```
```   497 qed (auto simp add: inf_rat_def sup_rat_def max_min_distrib2)
```
```   498
```
```   499 end
```
```   500
```
```   501 lemma positive_rat: "positive (Fract a b) \<longleftrightarrow> 0 < a * b"
```
```   502   by transfer simp
```
```   503
```
```   504 lemma less_rat [simp]:
```
```   505   assumes "b \<noteq> 0" and "d \<noteq> 0"
```
```   506   shows "Fract a b < Fract c d \<longleftrightarrow> (a * d) * (b * d) < (c * b) * (b * d)"
```
```   507   using assms unfolding less_rat_def
```
```   508   by (simp add: positive_rat algebra_simps)
```
```   509
```
```   510 lemma le_rat [simp]:
```
```   511   assumes "b \<noteq> 0" and "d \<noteq> 0"
```
```   512   shows "Fract a b \<le> Fract c d \<longleftrightarrow> (a * d) * (b * d) \<le> (c * b) * (b * d)"
```
```   513   using assms unfolding le_less by (simp add: eq_rat)
```
```   514
```
```   515 lemma abs_rat [simp, code]: "\<bar>Fract a b\<bar> = Fract \<bar>a\<bar> \<bar>b\<bar>"
```
```   516   by (auto simp add: abs_rat_def zabs_def Zero_rat_def not_less le_less eq_rat zero_less_mult_iff)
```
```   517
```
```   518 lemma sgn_rat [simp, code]: "sgn (Fract a b) = of_int (sgn a * sgn b)"
```
```   519   unfolding Fract_of_int_eq
```
```   520   by (auto simp: zsgn_def sgn_rat_def Zero_rat_def eq_rat)
```
```   521     (auto simp: rat_number_collapse not_less le_less zero_less_mult_iff)
```
```   522
```
```   523 lemma Rat_induct_pos [case_names Fract, induct type: rat]:
```
```   524   assumes step: "\<And>a b. 0 < b \<Longrightarrow> P (Fract a b)"
```
```   525   shows "P q"
```
```   526 proof (cases q)
```
```   527   have step': "\<And>a b. b < 0 \<Longrightarrow> P (Fract a b)"
```
```   528   proof -
```
```   529     fix a::int and b::int
```
```   530     assume b: "b < 0"
```
```   531     hence "0 < -b" by simp
```
```   532     hence "P (Fract (-a) (-b))" by (rule step)
```
```   533     thus "P (Fract a b)" by (simp add: order_less_imp_not_eq [OF b])
```
```   534   qed
```
```   535   case (Fract a b)
```
```   536   thus "P q" by (force simp add: linorder_neq_iff step step')
```
```   537 qed
```
```   538
```
```   539 lemma zero_less_Fract_iff:
```
```   540   "0 < b \<Longrightarrow> 0 < Fract a b \<longleftrightarrow> 0 < a"
```
```   541   by (simp add: Zero_rat_def zero_less_mult_iff)
```
```   542
```
```   543 lemma Fract_less_zero_iff:
```
```   544   "0 < b \<Longrightarrow> Fract a b < 0 \<longleftrightarrow> a < 0"
```
```   545   by (simp add: Zero_rat_def mult_less_0_iff)
```
```   546
```
```   547 lemma zero_le_Fract_iff:
```
```   548   "0 < b \<Longrightarrow> 0 \<le> Fract a b \<longleftrightarrow> 0 \<le> a"
```
```   549   by (simp add: Zero_rat_def zero_le_mult_iff)
```
```   550
```
```   551 lemma Fract_le_zero_iff:
```
```   552   "0 < b \<Longrightarrow> Fract a b \<le> 0 \<longleftrightarrow> a \<le> 0"
```
```   553   by (simp add: Zero_rat_def mult_le_0_iff)
```
```   554
```
```   555 lemma one_less_Fract_iff:
```
```   556   "0 < b \<Longrightarrow> 1 < Fract a b \<longleftrightarrow> b < a"
```
```   557   by (simp add: One_rat_def mult_less_cancel_right_disj)
```
```   558
```
```   559 lemma Fract_less_one_iff:
```
```   560   "0 < b \<Longrightarrow> Fract a b < 1 \<longleftrightarrow> a < b"
```
```   561   by (simp add: One_rat_def mult_less_cancel_right_disj)
```
```   562
```
```   563 lemma one_le_Fract_iff:
```
```   564   "0 < b \<Longrightarrow> 1 \<le> Fract a b \<longleftrightarrow> b \<le> a"
```
```   565   by (simp add: One_rat_def mult_le_cancel_right)
```
```   566
```
```   567 lemma Fract_le_one_iff:
```
```   568   "0 < b \<Longrightarrow> Fract a b \<le> 1 \<longleftrightarrow> a \<le> b"
```
```   569   by (simp add: One_rat_def mult_le_cancel_right)
```
```   570
```
```   571
```
```   572 subsubsection {* Rationals are an Archimedean field *}
```
```   573
```
```   574 lemma rat_floor_lemma:
```
```   575   shows "of_int (a div b) \<le> Fract a b \<and> Fract a b < of_int (a div b + 1)"
```
```   576 proof -
```
```   577   have "Fract a b = of_int (a div b) + Fract (a mod b) b"
```
```   578     by (cases "b = 0", simp, simp add: of_int_rat)
```
```   579   moreover have "0 \<le> Fract (a mod b) b \<and> Fract (a mod b) b < 1"
```
```   580     unfolding Fract_of_int_quotient
```
```   581     by (rule linorder_cases [of b 0]) (simp_all add: divide_nonpos_neg)
```
```   582   ultimately show ?thesis by simp
```
```   583 qed
```
```   584
```
```   585 instance rat :: archimedean_field
```
```   586 proof
```
```   587   fix r :: rat
```
```   588   show "\<exists>z. r \<le> of_int z"
```
```   589   proof (induct r)
```
```   590     case (Fract a b)
```
```   591     have "Fract a b \<le> of_int (a div b + 1)"
```
```   592       using rat_floor_lemma [of a b] by simp
```
```   593     then show "\<exists>z. Fract a b \<le> of_int z" ..
```
```   594   qed
```
```   595 qed
```
```   596
```
```   597 instantiation rat :: floor_ceiling
```
```   598 begin
```
```   599
```
```   600 definition [code del]:
```
```   601   "floor (x::rat) = (THE z. of_int z \<le> x \<and> x < of_int (z + 1))"
```
```   602
```
```   603 instance proof
```
```   604   fix x :: rat
```
```   605   show "of_int (floor x) \<le> x \<and> x < of_int (floor x + 1)"
```
```   606     unfolding floor_rat_def using floor_exists1 by (rule theI')
```
```   607 qed
```
```   608
```
```   609 end
```
```   610
```
```   611 lemma floor_Fract: "floor (Fract a b) = a div b"
```
```   612   using rat_floor_lemma [of a b]
```
```   613   by (simp add: floor_unique)
```
```   614
```
```   615
```
```   616 subsection {* Linear arithmetic setup *}
```
```   617
```
```   618 declaration {*
```
```   619   K (Lin_Arith.add_inj_thms [@{thm of_nat_le_iff} RS iffD2, @{thm of_nat_eq_iff} RS iffD2]
```
```   620     (* not needed because x < (y::nat) can be rewritten as Suc x <= y: of_nat_less_iff RS iffD2 *)
```
```   621   #> Lin_Arith.add_inj_thms [@{thm of_int_le_iff} RS iffD2, @{thm of_int_eq_iff} RS iffD2]
```
```   622     (* not needed because x < (y::int) can be rewritten as x + 1 <= y: of_int_less_iff RS iffD2 *)
```
```   623   #> Lin_Arith.add_simps [@{thm neg_less_iff_less},
```
```   624       @{thm True_implies_equals},
```
```   625       @{thm distrib_left [where a = "numeral v" for v]},
```
```   626       @{thm distrib_left [where a = "- numeral v" for v]},
```
```   627       @{thm divide_1}, @{thm divide_zero_left},
```
```   628       @{thm times_divide_eq_right}, @{thm times_divide_eq_left},
```
```   629       @{thm minus_divide_left} RS sym, @{thm minus_divide_right} RS sym,
```
```   630       @{thm of_int_minus}, @{thm of_int_diff},
```
```   631       @{thm of_int_of_nat_eq}]
```
```   632   #> Lin_Arith.add_simprocs Numeral_Simprocs.field_divide_cancel_numeral_factor
```
```   633   #> Lin_Arith.add_inj_const (@{const_name of_nat}, @{typ "nat => rat"})
```
```   634   #> Lin_Arith.add_inj_const (@{const_name of_int}, @{typ "int => rat"}))
```
```   635 *}
```
```   636
```
```   637
```
```   638 subsection {* Embedding from Rationals to other Fields *}
```
```   639
```
```   640 class field_char_0 = field + ring_char_0
```
```   641
```
```   642 subclass (in linordered_field) field_char_0 ..
```
```   643
```
```   644 context field_char_0
```
```   645 begin
```
```   646
```
```   647 lift_definition of_rat :: "rat \<Rightarrow> 'a"
```
```   648   is "\<lambda>x. of_int (fst x) / of_int (snd x)"
```
```   649 apply (clarsimp simp add: nonzero_divide_eq_eq nonzero_eq_divide_eq)
```
```   650 apply (simp only: of_int_mult [symmetric])
```
```   651 done
```
```   652
```
```   653 end
```
```   654
```
```   655 lemma of_rat_rat: "b \<noteq> 0 \<Longrightarrow> of_rat (Fract a b) = of_int a / of_int b"
```
```   656   by transfer simp
```
```   657
```
```   658 lemma of_rat_0 [simp]: "of_rat 0 = 0"
```
```   659   by transfer simp
```
```   660
```
```   661 lemma of_rat_1 [simp]: "of_rat 1 = 1"
```
```   662   by transfer simp
```
```   663
```
```   664 lemma of_rat_add: "of_rat (a + b) = of_rat a + of_rat b"
```
```   665   by transfer (simp add: add_frac_eq)
```
```   666
```
```   667 lemma of_rat_minus: "of_rat (- a) = - of_rat a"
```
```   668   by transfer simp
```
```   669
```
```   670 lemma of_rat_neg_one [simp]:
```
```   671   "of_rat (- 1) = - 1"
```
```   672   by (simp add: of_rat_minus)
```
```   673
```
```   674 lemma of_rat_diff: "of_rat (a - b) = of_rat a - of_rat b"
```
```   675   using of_rat_add [of a "- b"] by (simp add: of_rat_minus)
```
```   676
```
```   677 lemma of_rat_mult: "of_rat (a * b) = of_rat a * of_rat b"
```
```   678 apply transfer
```
```   679 apply (simp add: divide_inverse nonzero_inverse_mult_distrib ac_simps)
```
```   680 done
```
```   681
```
```   682 lemma nonzero_of_rat_inverse:
```
```   683   "a \<noteq> 0 \<Longrightarrow> of_rat (inverse a) = inverse (of_rat a)"
```
```   684 apply (rule inverse_unique [symmetric])
```
```   685 apply (simp add: of_rat_mult [symmetric])
```
```   686 done
```
```   687
```
```   688 lemma of_rat_inverse:
```
```   689   "(of_rat (inverse a)::'a::{field_char_0, field_inverse_zero}) =
```
```   690    inverse (of_rat a)"
```
```   691 by (cases "a = 0", simp_all add: nonzero_of_rat_inverse)
```
```   692
```
```   693 lemma nonzero_of_rat_divide:
```
```   694   "b \<noteq> 0 \<Longrightarrow> of_rat (a / b) = of_rat a / of_rat b"
```
```   695 by (simp add: divide_inverse of_rat_mult nonzero_of_rat_inverse)
```
```   696
```
```   697 lemma of_rat_divide:
```
```   698   "(of_rat (a / b)::'a::{field_char_0, field_inverse_zero})
```
```   699    = of_rat a / of_rat b"
```
```   700 by (cases "b = 0") (simp_all add: nonzero_of_rat_divide)
```
```   701
```
```   702 lemma of_rat_power:
```
```   703   "(of_rat (a ^ n)::'a::field_char_0) = of_rat a ^ n"
```
```   704 by (induct n) (simp_all add: of_rat_mult)
```
```   705
```
```   706 lemma of_rat_eq_iff [simp]: "(of_rat a = of_rat b) = (a = b)"
```
```   707 apply transfer
```
```   708 apply (simp add: nonzero_divide_eq_eq nonzero_eq_divide_eq)
```
```   709 apply (simp only: of_int_mult [symmetric] of_int_eq_iff)
```
```   710 done
```
```   711
```
```   712 lemma of_rat_eq_0_iff [simp]: "(of_rat a = 0) = (a = 0)"
```
```   713   using of_rat_eq_iff [of _ 0] by simp
```
```   714
```
```   715 lemma zero_eq_of_rat_iff [simp]: "(0 = of_rat a) = (0 = a)"
```
```   716   by simp
```
```   717
```
```   718 lemma of_rat_eq_1_iff [simp]: "(of_rat a = 1) = (a = 1)"
```
```   719   using of_rat_eq_iff [of _ 1] by simp
```
```   720
```
```   721 lemma one_eq_of_rat_iff [simp]: "(1 = of_rat a) = (1 = a)"
```
```   722   by simp
```
```   723
```
```   724 lemma of_rat_less:
```
```   725   "(of_rat r :: 'a::linordered_field) < of_rat s \<longleftrightarrow> r < s"
```
```   726 proof (induct r, induct s)
```
```   727   fix a b c d :: int
```
```   728   assume not_zero: "b > 0" "d > 0"
```
```   729   then have "b * d > 0" by simp
```
```   730   have of_int_divide_less_eq:
```
```   731     "(of_int a :: 'a) / of_int b < of_int c / of_int d
```
```   732       \<longleftrightarrow> (of_int a :: 'a) * of_int d < of_int c * of_int b"
```
```   733     using not_zero by (simp add: pos_less_divide_eq pos_divide_less_eq)
```
```   734   show "(of_rat (Fract a b) :: 'a::linordered_field) < of_rat (Fract c d)
```
```   735     \<longleftrightarrow> Fract a b < Fract c d"
```
```   736     using not_zero `b * d > 0`
```
```   737     by (simp add: of_rat_rat of_int_divide_less_eq of_int_mult [symmetric] del: of_int_mult)
```
```   738 qed
```
```   739
```
```   740 lemma of_rat_less_eq:
```
```   741   "(of_rat r :: 'a::linordered_field) \<le> of_rat s \<longleftrightarrow> r \<le> s"
```
```   742   unfolding le_less by (auto simp add: of_rat_less)
```
```   743
```
```   744 lemma of_rat_le_0_iff [simp]: "((of_rat r :: 'a::linordered_field) \<le> 0) = (r \<le> 0)"
```
```   745   using of_rat_less_eq [of r 0, where 'a='a] by simp
```
```   746
```
```   747 lemma zero_le_of_rat_iff [simp]: "(0 \<le> (of_rat r :: 'a::linordered_field)) = (0 \<le> r)"
```
```   748   using of_rat_less_eq [of 0 r, where 'a='a] by simp
```
```   749
```
```   750 lemma of_rat_le_1_iff [simp]: "((of_rat r :: 'a::linordered_field) \<le> 1) = (r \<le> 1)"
```
```   751   using of_rat_less_eq [of r 1] by simp
```
```   752
```
```   753 lemma one_le_of_rat_iff [simp]: "(1 \<le> (of_rat r :: 'a::linordered_field)) = (1 \<le> r)"
```
```   754   using of_rat_less_eq [of 1 r] by simp
```
```   755
```
```   756 lemma of_rat_less_0_iff [simp]: "((of_rat r :: 'a::linordered_field) < 0) = (r < 0)"
```
```   757   using of_rat_less [of r 0, where 'a='a] by simp
```
```   758
```
```   759 lemma zero_less_of_rat_iff [simp]: "(0 < (of_rat r :: 'a::linordered_field)) = (0 < r)"
```
```   760   using of_rat_less [of 0 r, where 'a='a] by simp
```
```   761
```
```   762 lemma of_rat_less_1_iff [simp]: "((of_rat r :: 'a::linordered_field) < 1) = (r < 1)"
```
```   763   using of_rat_less [of r 1] by simp
```
```   764
```
```   765 lemma one_less_of_rat_iff [simp]: "(1 < (of_rat r :: 'a::linordered_field)) = (1 < r)"
```
```   766   using of_rat_less [of 1 r] by simp
```
```   767
```
```   768 lemma of_rat_eq_id [simp]: "of_rat = id"
```
```   769 proof
```
```   770   fix a
```
```   771   show "of_rat a = id a"
```
```   772   by (induct a)
```
```   773      (simp add: of_rat_rat Fract_of_int_eq [symmetric])
```
```   774 qed
```
```   775
```
```   776 text{*Collapse nested embeddings*}
```
```   777 lemma of_rat_of_nat_eq [simp]: "of_rat (of_nat n) = of_nat n"
```
```   778 by (induct n) (simp_all add: of_rat_add)
```
```   779
```
```   780 lemma of_rat_of_int_eq [simp]: "of_rat (of_int z) = of_int z"
```
```   781 by (cases z rule: int_diff_cases) (simp add: of_rat_diff)
```
```   782
```
```   783 lemma of_rat_numeral_eq [simp]:
```
```   784   "of_rat (numeral w) = numeral w"
```
```   785 using of_rat_of_int_eq [of "numeral w"] by simp
```
```   786
```
```   787 lemma of_rat_neg_numeral_eq [simp]:
```
```   788   "of_rat (- numeral w) = - numeral w"
```
```   789 using of_rat_of_int_eq [of "- numeral w"] by simp
```
```   790
```
```   791 lemmas zero_rat = Zero_rat_def
```
```   792 lemmas one_rat = One_rat_def
```
```   793
```
```   794 abbreviation
```
```   795   rat_of_nat :: "nat \<Rightarrow> rat"
```
```   796 where
```
```   797   "rat_of_nat \<equiv> of_nat"
```
```   798
```
```   799 abbreviation
```
```   800   rat_of_int :: "int \<Rightarrow> rat"
```
```   801 where
```
```   802   "rat_of_int \<equiv> of_int"
```
```   803
```
```   804 subsection {* The Set of Rational Numbers *}
```
```   805
```
```   806 context field_char_0
```
```   807 begin
```
```   808
```
```   809 definition
```
```   810   Rats  :: "'a set" where
```
```   811   "Rats = range of_rat"
```
```   812
```
```   813 notation (xsymbols)
```
```   814   Rats  ("\<rat>")
```
```   815
```
```   816 end
```
```   817
```
```   818 lemma Rats_of_rat [simp]: "of_rat r \<in> Rats"
```
```   819 by (simp add: Rats_def)
```
```   820
```
```   821 lemma Rats_of_int [simp]: "of_int z \<in> Rats"
```
```   822 by (subst of_rat_of_int_eq [symmetric], rule Rats_of_rat)
```
```   823
```
```   824 lemma Rats_of_nat [simp]: "of_nat n \<in> Rats"
```
```   825 by (subst of_rat_of_nat_eq [symmetric], rule Rats_of_rat)
```
```   826
```
```   827 lemma Rats_number_of [simp]: "numeral w \<in> Rats"
```
```   828 by (subst of_rat_numeral_eq [symmetric], rule Rats_of_rat)
```
```   829
```
```   830 lemma Rats_0 [simp]: "0 \<in> Rats"
```
```   831 apply (unfold Rats_def)
```
```   832 apply (rule range_eqI)
```
```   833 apply (rule of_rat_0 [symmetric])
```
```   834 done
```
```   835
```
```   836 lemma Rats_1 [simp]: "1 \<in> Rats"
```
```   837 apply (unfold Rats_def)
```
```   838 apply (rule range_eqI)
```
```   839 apply (rule of_rat_1 [symmetric])
```
```   840 done
```
```   841
```
```   842 lemma Rats_add [simp]: "\<lbrakk>a \<in> Rats; b \<in> Rats\<rbrakk> \<Longrightarrow> a + b \<in> Rats"
```
```   843 apply (auto simp add: Rats_def)
```
```   844 apply (rule range_eqI)
```
```   845 apply (rule of_rat_add [symmetric])
```
```   846 done
```
```   847
```
```   848 lemma Rats_minus [simp]: "a \<in> Rats \<Longrightarrow> - a \<in> Rats"
```
```   849 apply (auto simp add: Rats_def)
```
```   850 apply (rule range_eqI)
```
```   851 apply (rule of_rat_minus [symmetric])
```
```   852 done
```
```   853
```
```   854 lemma Rats_diff [simp]: "\<lbrakk>a \<in> Rats; b \<in> Rats\<rbrakk> \<Longrightarrow> a - b \<in> Rats"
```
```   855 apply (auto simp add: Rats_def)
```
```   856 apply (rule range_eqI)
```
```   857 apply (rule of_rat_diff [symmetric])
```
```   858 done
```
```   859
```
```   860 lemma Rats_mult [simp]: "\<lbrakk>a \<in> Rats; b \<in> Rats\<rbrakk> \<Longrightarrow> a * b \<in> Rats"
```
```   861 apply (auto simp add: Rats_def)
```
```   862 apply (rule range_eqI)
```
```   863 apply (rule of_rat_mult [symmetric])
```
```   864 done
```
```   865
```
```   866 lemma nonzero_Rats_inverse:
```
```   867   fixes a :: "'a::field_char_0"
```
```   868   shows "\<lbrakk>a \<in> Rats; a \<noteq> 0\<rbrakk> \<Longrightarrow> inverse a \<in> Rats"
```
```   869 apply (auto simp add: Rats_def)
```
```   870 apply (rule range_eqI)
```
```   871 apply (erule nonzero_of_rat_inverse [symmetric])
```
```   872 done
```
```   873
```
```   874 lemma Rats_inverse [simp]:
```
```   875   fixes a :: "'a::{field_char_0, field_inverse_zero}"
```
```   876   shows "a \<in> Rats \<Longrightarrow> inverse a \<in> Rats"
```
```   877 apply (auto simp add: Rats_def)
```
```   878 apply (rule range_eqI)
```
```   879 apply (rule of_rat_inverse [symmetric])
```
```   880 done
```
```   881
```
```   882 lemma nonzero_Rats_divide:
```
```   883   fixes a b :: "'a::field_char_0"
```
```   884   shows "\<lbrakk>a \<in> Rats; b \<in> Rats; b \<noteq> 0\<rbrakk> \<Longrightarrow> a / b \<in> Rats"
```
```   885 apply (auto simp add: Rats_def)
```
```   886 apply (rule range_eqI)
```
```   887 apply (erule nonzero_of_rat_divide [symmetric])
```
```   888 done
```
```   889
```
```   890 lemma Rats_divide [simp]:
```
```   891   fixes a b :: "'a::{field_char_0, field_inverse_zero}"
```
```   892   shows "\<lbrakk>a \<in> Rats; b \<in> Rats\<rbrakk> \<Longrightarrow> a / b \<in> Rats"
```
```   893 apply (auto simp add: Rats_def)
```
```   894 apply (rule range_eqI)
```
```   895 apply (rule of_rat_divide [symmetric])
```
```   896 done
```
```   897
```
```   898 lemma Rats_power [simp]:
```
```   899   fixes a :: "'a::field_char_0"
```
```   900   shows "a \<in> Rats \<Longrightarrow> a ^ n \<in> Rats"
```
```   901 apply (auto simp add: Rats_def)
```
```   902 apply (rule range_eqI)
```
```   903 apply (rule of_rat_power [symmetric])
```
```   904 done
```
```   905
```
```   906 lemma Rats_cases [cases set: Rats]:
```
```   907   assumes "q \<in> \<rat>"
```
```   908   obtains (of_rat) r where "q = of_rat r"
```
```   909 proof -
```
```   910   from `q \<in> \<rat>` have "q \<in> range of_rat" unfolding Rats_def .
```
```   911   then obtain r where "q = of_rat r" ..
```
```   912   then show thesis ..
```
```   913 qed
```
```   914
```
```   915 lemma Rats_induct [case_names of_rat, induct set: Rats]:
```
```   916   "q \<in> \<rat> \<Longrightarrow> (\<And>r. P (of_rat r)) \<Longrightarrow> P q"
```
```   917   by (rule Rats_cases) auto
```
```   918
```
```   919 lemma Rats_infinite: "\<not> finite \<rat>"
```
```   920   by (auto dest!: finite_imageD simp: inj_on_def infinite_UNIV_char_0 Rats_def)
```
```   921
```
```   922 subsection {* Implementation of rational numbers as pairs of integers *}
```
```   923
```
```   924 text {* Formal constructor *}
```
```   925
```
```   926 definition Frct :: "int \<times> int \<Rightarrow> rat" where
```
```   927   [simp]: "Frct p = Fract (fst p) (snd p)"
```
```   928
```
```   929 lemma [code abstype]:
```
```   930   "Frct (quotient_of q) = q"
```
```   931   by (cases q) (auto intro: quotient_of_eq)
```
```   932
```
```   933
```
```   934 text {* Numerals *}
```
```   935
```
```   936 declare quotient_of_Fract [code abstract]
```
```   937
```
```   938 definition of_int :: "int \<Rightarrow> rat"
```
```   939 where
```
```   940   [code_abbrev]: "of_int = Int.of_int"
```
```   941 hide_const (open) of_int
```
```   942
```
```   943 lemma quotient_of_int [code abstract]:
```
```   944   "quotient_of (Rat.of_int a) = (a, 1)"
```
```   945   by (simp add: of_int_def of_int_rat quotient_of_Fract)
```
```   946
```
```   947 lemma [code_unfold]:
```
```   948   "numeral k = Rat.of_int (numeral k)"
```
```   949   by (simp add: Rat.of_int_def)
```
```   950
```
```   951 lemma [code_unfold]:
```
```   952   "- numeral k = Rat.of_int (- numeral k)"
```
```   953   by (simp add: Rat.of_int_def)
```
```   954
```
```   955 lemma Frct_code_post [code_post]:
```
```   956   "Frct (0, a) = 0"
```
```   957   "Frct (a, 0) = 0"
```
```   958   "Frct (1, 1) = 1"
```
```   959   "Frct (numeral k, 1) = numeral k"
```
```   960   "Frct (1, numeral k) = 1 / numeral k"
```
```   961   "Frct (numeral k, numeral l) = numeral k / numeral l"
```
```   962   "Frct (- a, b) = - Frct (a, b)"
```
```   963   "Frct (a, - b) = - Frct (a, b)"
```
```   964   "- (- Frct q) = Frct q"
```
```   965   by (simp_all add: Fract_of_int_quotient)
```
```   966
```
```   967
```
```   968 text {* Operations *}
```
```   969
```
```   970 lemma rat_zero_code [code abstract]:
```
```   971   "quotient_of 0 = (0, 1)"
```
```   972   by (simp add: Zero_rat_def quotient_of_Fract normalize_def)
```
```   973
```
```   974 lemma rat_one_code [code abstract]:
```
```   975   "quotient_of 1 = (1, 1)"
```
```   976   by (simp add: One_rat_def quotient_of_Fract normalize_def)
```
```   977
```
```   978 lemma rat_plus_code [code abstract]:
```
```   979   "quotient_of (p + q) = (let (a, c) = quotient_of p; (b, d) = quotient_of q
```
```   980      in normalize (a * d + b * c, c * d))"
```
```   981   by (cases p, cases q) (simp add: quotient_of_Fract)
```
```   982
```
```   983 lemma rat_uminus_code [code abstract]:
```
```   984   "quotient_of (- p) = (let (a, b) = quotient_of p in (- a, b))"
```
```   985   by (cases p) (simp add: quotient_of_Fract)
```
```   986
```
```   987 lemma rat_minus_code [code abstract]:
```
```   988   "quotient_of (p - q) = (let (a, c) = quotient_of p; (b, d) = quotient_of q
```
```   989      in normalize (a * d - b * c, c * d))"
```
```   990   by (cases p, cases q) (simp add: quotient_of_Fract)
```
```   991
```
```   992 lemma rat_times_code [code abstract]:
```
```   993   "quotient_of (p * q) = (let (a, c) = quotient_of p; (b, d) = quotient_of q
```
```   994      in normalize (a * b, c * d))"
```
```   995   by (cases p, cases q) (simp add: quotient_of_Fract)
```
```   996
```
```   997 lemma rat_inverse_code [code abstract]:
```
```   998   "quotient_of (inverse p) = (let (a, b) = quotient_of p
```
```   999     in if a = 0 then (0, 1) else (sgn a * b, \<bar>a\<bar>))"
```
```  1000 proof (cases p)
```
```  1001   case (Fract a b) then show ?thesis
```
```  1002     by (cases "0::int" a rule: linorder_cases) (simp_all add: quotient_of_Fract gcd_int.commute)
```
```  1003 qed
```
```  1004
```
```  1005 lemma rat_divide_code [code abstract]:
```
```  1006   "quotient_of (p / q) = (let (a, c) = quotient_of p; (b, d) = quotient_of q
```
```  1007      in normalize (a * d, c * b))"
```
```  1008   by (cases p, cases q) (simp add: quotient_of_Fract)
```
```  1009
```
```  1010 lemma rat_abs_code [code abstract]:
```
```  1011   "quotient_of \<bar>p\<bar> = (let (a, b) = quotient_of p in (\<bar>a\<bar>, b))"
```
```  1012   by (cases p) (simp add: quotient_of_Fract)
```
```  1013
```
```  1014 lemma rat_sgn_code [code abstract]:
```
```  1015   "quotient_of (sgn p) = (sgn (fst (quotient_of p)), 1)"
```
```  1016 proof (cases p)
```
```  1017   case (Fract a b) then show ?thesis
```
```  1018   by (cases "0::int" a rule: linorder_cases) (simp_all add: quotient_of_Fract)
```
```  1019 qed
```
```  1020
```
```  1021 lemma rat_floor_code [code]:
```
```  1022   "floor p = (let (a, b) = quotient_of p in a div b)"
```
```  1023 by (cases p) (simp add: quotient_of_Fract floor_Fract)
```
```  1024
```
```  1025 instantiation rat :: equal
```
```  1026 begin
```
```  1027
```
```  1028 definition [code]:
```
```  1029   "HOL.equal a b \<longleftrightarrow> quotient_of a = quotient_of b"
```
```  1030
```
```  1031 instance proof
```
```  1032 qed (simp add: equal_rat_def quotient_of_inject_eq)
```
```  1033
```
```  1034 lemma rat_eq_refl [code nbe]:
```
```  1035   "HOL.equal (r::rat) r \<longleftrightarrow> True"
```
```  1036   by (rule equal_refl)
```
```  1037
```
```  1038 end
```
```  1039
```
```  1040 lemma rat_less_eq_code [code]:
```
```  1041   "p \<le> q \<longleftrightarrow> (let (a, c) = quotient_of p; (b, d) = quotient_of q in a * d \<le> c * b)"
```
```  1042   by (cases p, cases q) (simp add: quotient_of_Fract mult.commute)
```
```  1043
```
```  1044 lemma rat_less_code [code]:
```
```  1045   "p < q \<longleftrightarrow> (let (a, c) = quotient_of p; (b, d) = quotient_of q in a * d < c * b)"
```
```  1046   by (cases p, cases q) (simp add: quotient_of_Fract mult.commute)
```
```  1047
```
```  1048 lemma [code]:
```
```  1049   "of_rat p = (let (a, b) = quotient_of p in of_int a / of_int b)"
```
```  1050   by (cases p) (simp add: quotient_of_Fract of_rat_rat)
```
```  1051
```
```  1052
```
```  1053 text {* Quickcheck *}
```
```  1054
```
```  1055 definition (in term_syntax)
```
```  1056   valterm_fract :: "int \<times> (unit \<Rightarrow> Code_Evaluation.term) \<Rightarrow> int \<times> (unit \<Rightarrow> Code_Evaluation.term) \<Rightarrow> rat \<times> (unit \<Rightarrow> Code_Evaluation.term)" where
```
```  1057   [code_unfold]: "valterm_fract k l = Code_Evaluation.valtermify Fract {\<cdot>} k {\<cdot>} l"
```
```  1058
```
```  1059 notation fcomp (infixl "\<circ>>" 60)
```
```  1060 notation scomp (infixl "\<circ>\<rightarrow>" 60)
```
```  1061
```
```  1062 instantiation rat :: random
```
```  1063 begin
```
```  1064
```
```  1065 definition
```
```  1066   "Quickcheck_Random.random i = Quickcheck_Random.random i \<circ>\<rightarrow> (\<lambda>num. Random.range i \<circ>\<rightarrow> (\<lambda>denom. Pair (
```
```  1067      let j = int_of_integer (integer_of_natural (denom + 1))
```
```  1068      in valterm_fract num (j, \<lambda>u. Code_Evaluation.term_of j))))"
```
```  1069
```
```  1070 instance ..
```
```  1071
```
```  1072 end
```
```  1073
```
```  1074 no_notation fcomp (infixl "\<circ>>" 60)
```
```  1075 no_notation scomp (infixl "\<circ>\<rightarrow>" 60)
```
```  1076
```
```  1077 instantiation rat :: exhaustive
```
```  1078 begin
```
```  1079
```
```  1080 definition
```
```  1081   "exhaustive_rat f d = Quickcheck_Exhaustive.exhaustive
```
```  1082     (\<lambda>l. Quickcheck_Exhaustive.exhaustive (\<lambda>k. f (Fract k (int_of_integer (integer_of_natural l) + 1))) d) d"
```
```  1083
```
```  1084 instance ..
```
```  1085
```
```  1086 end
```
```  1087
```
```  1088 instantiation rat :: full_exhaustive
```
```  1089 begin
```
```  1090
```
```  1091 definition
```
```  1092   "full_exhaustive_rat f d = Quickcheck_Exhaustive.full_exhaustive (%(l, _). Quickcheck_Exhaustive.full_exhaustive (%k.
```
```  1093      f (let j = int_of_integer (integer_of_natural l) + 1
```
```  1094         in valterm_fract k (j, %_. Code_Evaluation.term_of j))) d) d"
```
```  1095
```
```  1096 instance ..
```
```  1097
```
```  1098 end
```
```  1099
```
```  1100 instantiation rat :: partial_term_of
```
```  1101 begin
```
```  1102
```
```  1103 instance ..
```
```  1104
```
```  1105 end
```
```  1106
```
```  1107 lemma [code]:
```
```  1108   "partial_term_of (ty :: rat itself) (Quickcheck_Narrowing.Narrowing_variable p tt) == Code_Evaluation.Free (STR ''_'') (Typerep.Typerep (STR ''Rat.rat'') [])"
```
```  1109   "partial_term_of (ty :: rat itself) (Quickcheck_Narrowing.Narrowing_constructor 0 [l, k]) ==
```
```  1110      Code_Evaluation.App (Code_Evaluation.Const (STR ''Rat.Frct'')
```
```  1111      (Typerep.Typerep (STR ''fun'') [Typerep.Typerep (STR ''Product_Type.prod'') [Typerep.Typerep (STR ''Int.int'') [], Typerep.Typerep (STR ''Int.int'') []],
```
```  1112         Typerep.Typerep (STR ''Rat.rat'') []])) (Code_Evaluation.App (Code_Evaluation.App (Code_Evaluation.Const (STR ''Product_Type.Pair'') (Typerep.Typerep (STR ''fun'') [Typerep.Typerep (STR ''Int.int'') [], Typerep.Typerep (STR ''fun'') [Typerep.Typerep (STR ''Int.int'') [], Typerep.Typerep (STR ''Product_Type.prod'') [Typerep.Typerep (STR ''Int.int'') [], Typerep.Typerep (STR ''Int.int'') []]]])) (partial_term_of (TYPE(int)) l)) (partial_term_of (TYPE(int)) k))"
```
```  1113 by (rule partial_term_of_anything)+
```
```  1114
```
```  1115 instantiation rat :: narrowing
```
```  1116 begin
```
```  1117
```
```  1118 definition
```
```  1119   "narrowing = Quickcheck_Narrowing.apply (Quickcheck_Narrowing.apply
```
```  1120     (Quickcheck_Narrowing.cons (%nom denom. Fract nom denom)) narrowing) narrowing"
```
```  1121
```
```  1122 instance ..
```
```  1123
```
```  1124 end
```
```  1125
```
```  1126
```
```  1127 subsection {* Setup for Nitpick *}
```
```  1128
```
```  1129 declaration {*
```
```  1130   Nitpick_HOL.register_frac_type @{type_name rat}
```
```  1131    [(@{const_name zero_rat_inst.zero_rat}, @{const_name Nitpick.zero_frac}),
```
```  1132     (@{const_name one_rat_inst.one_rat}, @{const_name Nitpick.one_frac}),
```
```  1133     (@{const_name plus_rat_inst.plus_rat}, @{const_name Nitpick.plus_frac}),
```
```  1134     (@{const_name times_rat_inst.times_rat}, @{const_name Nitpick.times_frac}),
```
```  1135     (@{const_name uminus_rat_inst.uminus_rat}, @{const_name Nitpick.uminus_frac}),
```
```  1136     (@{const_name inverse_rat_inst.inverse_rat}, @{const_name Nitpick.inverse_frac}),
```
```  1137     (@{const_name ord_rat_inst.less_rat}, @{const_name Nitpick.less_frac}),
```
```  1138     (@{const_name ord_rat_inst.less_eq_rat}, @{const_name Nitpick.less_eq_frac}),
```
```  1139     (@{const_name field_char_0_class.of_rat}, @{const_name Nitpick.of_frac})]
```
```  1140 *}
```
```  1141
```
```  1142 lemmas [nitpick_unfold] = inverse_rat_inst.inverse_rat
```
```  1143   one_rat_inst.one_rat ord_rat_inst.less_rat
```
```  1144   ord_rat_inst.less_eq_rat plus_rat_inst.plus_rat times_rat_inst.times_rat
```
```  1145   uminus_rat_inst.uminus_rat zero_rat_inst.zero_rat
```
```  1146
```
```  1147
```
```  1148 subsection {* Float syntax *}
```
```  1149
```
```  1150 syntax "_Float" :: "float_const \<Rightarrow> 'a"    ("_")
```
```  1151
```
```  1152 parse_translation {*
```
```  1153   let
```
```  1154     fun mk_frac str =
```
```  1155       let
```
```  1156         val {mant = i, exp = n} = Lexicon.read_float str;
```
```  1157         val exp = Syntax.const @{const_syntax Power.power};
```
```  1158         val ten = Numeral.mk_number_syntax 10;
```
```  1159         val exp10 = if n = 1 then ten else exp \$ ten \$ Numeral.mk_number_syntax n;;
```
```  1160       in Syntax.const @{const_syntax divide} \$ Numeral.mk_number_syntax i \$ exp10 end;
```
```  1161
```
```  1162     fun float_tr [(c as Const (@{syntax_const "_constrain"}, _)) \$ t \$ u] = c \$ float_tr [t] \$ u
```
```  1163       | float_tr [t as Const (str, _)] = mk_frac str
```
```  1164       | float_tr ts = raise TERM ("float_tr", ts);
```
```  1165   in [(@{syntax_const "_Float"}, K float_tr)] end
```
```  1166 *}
```
```  1167
```
```  1168 text{* Test: *}
```
```  1169 lemma "123.456 = -111.111 + 200 + 30 + 4 + 5/10 + 6/100 + (7/1000::rat)"
```
```  1170   by simp
```
```  1171
```
```  1172
```
```  1173 subsection {* Hiding implementation details *}
```
```  1174
```
```  1175 hide_const (open) normalize positive
```
```  1176
```
```  1177 lifting_update rat.lifting
```
```  1178 lifting_forget rat.lifting
```
```  1179
```
```  1180 end
```
```  1181
```