src/HOL/RealDef.thy
 author haftmann Mon May 11 15:18:32 2009 +0200 (2009-05-11) changeset 31100 6a2e67fe4488 parent 30242 aea5d7fa7ef5 child 31203 5c8fb4fd67e0 permissions -rw-r--r--
tuned interface of Lin_Arith
```     1 (*  Title       : HOL/RealDef.thy
```
```     2     Author      : Jacques D. Fleuriot
```
```     3     Copyright   : 1998  University of Cambridge
```
```     4     Conversion to Isar and new proofs by Lawrence C Paulson, 2003/4
```
```     5     Additional contributions by Jeremy Avigad
```
```     6 *)
```
```     7
```
```     8 header{*Defining the Reals from the Positive Reals*}
```
```     9
```
```    10 theory RealDef
```
```    11 imports PReal
```
```    12 begin
```
```    13
```
```    14 definition
```
```    15   realrel   ::  "((preal * preal) * (preal * preal)) set" where
```
```    16   [code del]: "realrel = {p. \<exists>x1 y1 x2 y2. p = ((x1,y1),(x2,y2)) & x1+y2 = x2+y1}"
```
```    17
```
```    18 typedef (Real)  real = "UNIV//realrel"
```
```    19   by (auto simp add: quotient_def)
```
```    20
```
```    21 definition
```
```    22   (** these don't use the overloaded "real" function: users don't see them **)
```
```    23   real_of_preal :: "preal => real" where
```
```    24   [code del]: "real_of_preal m = Abs_Real (realrel `` {(m + 1, 1)})"
```
```    25
```
```    26 instantiation real :: "{zero, one, plus, minus, uminus, times, inverse, ord, abs, sgn}"
```
```    27 begin
```
```    28
```
```    29 definition
```
```    30   real_zero_def [code del]: "0 = Abs_Real(realrel``{(1, 1)})"
```
```    31
```
```    32 definition
```
```    33   real_one_def [code del]: "1 = Abs_Real(realrel``{(1 + 1, 1)})"
```
```    34
```
```    35 definition
```
```    36   real_add_def [code del]: "z + w =
```
```    37        contents (\<Union>(x,y) \<in> Rep_Real(z). \<Union>(u,v) \<in> Rep_Real(w).
```
```    38                  { Abs_Real(realrel``{(x+u, y+v)}) })"
```
```    39
```
```    40 definition
```
```    41   real_minus_def [code del]: "- r =  contents (\<Union>(x,y) \<in> Rep_Real(r). { Abs_Real(realrel``{(y,x)}) })"
```
```    42
```
```    43 definition
```
```    44   real_diff_def [code del]: "r - (s::real) = r + - s"
```
```    45
```
```    46 definition
```
```    47   real_mult_def [code del]:
```
```    48     "z * w =
```
```    49        contents (\<Union>(x,y) \<in> Rep_Real(z). \<Union>(u,v) \<in> Rep_Real(w).
```
```    50                  { Abs_Real(realrel``{(x*u + y*v, x*v + y*u)}) })"
```
```    51
```
```    52 definition
```
```    53   real_inverse_def [code del]: "inverse (R::real) = (THE S. (R = 0 & S = 0) | S * R = 1)"
```
```    54
```
```    55 definition
```
```    56   real_divide_def [code del]: "R / (S::real) = R * inverse S"
```
```    57
```
```    58 definition
```
```    59   real_le_def [code del]: "z \<le> (w::real) \<longleftrightarrow>
```
```    60     (\<exists>x y u v. x+v \<le> u+y & (x,y) \<in> Rep_Real z & (u,v) \<in> Rep_Real w)"
```
```    61
```
```    62 definition
```
```    63   real_less_def [code del]: "x < (y\<Colon>real) \<longleftrightarrow> x \<le> y \<and> x \<noteq> y"
```
```    64
```
```    65 definition
```
```    66   real_abs_def:  "abs (r::real) = (if r < 0 then - r else r)"
```
```    67
```
```    68 definition
```
```    69   real_sgn_def: "sgn (x::real) = (if x=0 then 0 else if 0<x then 1 else - 1)"
```
```    70
```
```    71 instance ..
```
```    72
```
```    73 end
```
```    74
```
```    75 subsection {* Equivalence relation over positive reals *}
```
```    76
```
```    77 lemma preal_trans_lemma:
```
```    78   assumes "x + y1 = x1 + y"
```
```    79       and "x + y2 = x2 + y"
```
```    80   shows "x1 + y2 = x2 + (y1::preal)"
```
```    81 proof -
```
```    82   have "(x1 + y2) + x = (x + y2) + x1" by (simp add: add_ac)
```
```    83   also have "... = (x2 + y) + x1"  by (simp add: prems)
```
```    84   also have "... = x2 + (x1 + y)"  by (simp add: add_ac)
```
```    85   also have "... = x2 + (x + y1)"  by (simp add: prems)
```
```    86   also have "... = (x2 + y1) + x"  by (simp add: add_ac)
```
```    87   finally have "(x1 + y2) + x = (x2 + y1) + x" .
```
```    88   thus ?thesis by (rule add_right_imp_eq)
```
```    89 qed
```
```    90
```
```    91
```
```    92 lemma realrel_iff [simp]: "(((x1,y1),(x2,y2)) \<in> realrel) = (x1 + y2 = x2 + y1)"
```
```    93 by (simp add: realrel_def)
```
```    94
```
```    95 lemma equiv_realrel: "equiv UNIV realrel"
```
```    96 apply (auto simp add: equiv_def refl_on_def sym_def trans_def realrel_def)
```
```    97 apply (blast dest: preal_trans_lemma)
```
```    98 done
```
```    99
```
```   100 text{*Reduces equality of equivalence classes to the @{term realrel} relation:
```
```   101   @{term "(realrel `` {x} = realrel `` {y}) = ((x,y) \<in> realrel)"} *}
```
```   102 lemmas equiv_realrel_iff =
```
```   103        eq_equiv_class_iff [OF equiv_realrel UNIV_I UNIV_I]
```
```   104
```
```   105 declare equiv_realrel_iff [simp]
```
```   106
```
```   107
```
```   108 lemma realrel_in_real [simp]: "realrel``{(x,y)}: Real"
```
```   109 by (simp add: Real_def realrel_def quotient_def, blast)
```
```   110
```
```   111 declare Abs_Real_inject [simp]
```
```   112 declare Abs_Real_inverse [simp]
```
```   113
```
```   114
```
```   115 text{*Case analysis on the representation of a real number as an equivalence
```
```   116       class of pairs of positive reals.*}
```
```   117 lemma eq_Abs_Real [case_names Abs_Real, cases type: real]:
```
```   118      "(!!x y. z = Abs_Real(realrel``{(x,y)}) ==> P) ==> P"
```
```   119 apply (rule Rep_Real [of z, unfolded Real_def, THEN quotientE])
```
```   120 apply (drule arg_cong [where f=Abs_Real])
```
```   121 apply (auto simp add: Rep_Real_inverse)
```
```   122 done
```
```   123
```
```   124
```
```   125 subsection {* Addition and Subtraction *}
```
```   126
```
```   127 lemma real_add_congruent2_lemma:
```
```   128      "[|a + ba = aa + b; ab + bc = ac + bb|]
```
```   129       ==> a + ab + (ba + bc) = aa + ac + (b + (bb::preal))"
```
```   130 apply (simp add: add_assoc)
```
```   131 apply (rule add_left_commute [of ab, THEN ssubst])
```
```   132 apply (simp add: add_assoc [symmetric])
```
```   133 apply (simp add: add_ac)
```
```   134 done
```
```   135
```
```   136 lemma real_add:
```
```   137      "Abs_Real (realrel``{(x,y)}) + Abs_Real (realrel``{(u,v)}) =
```
```   138       Abs_Real (realrel``{(x+u, y+v)})"
```
```   139 proof -
```
```   140   have "(\<lambda>z w. (\<lambda>(x,y). (\<lambda>(u,v). {Abs_Real (realrel `` {(x+u, y+v)})}) w) z)
```
```   141         respects2 realrel"
```
```   142     by (simp add: congruent2_def, blast intro: real_add_congruent2_lemma)
```
```   143   thus ?thesis
```
```   144     by (simp add: real_add_def UN_UN_split_split_eq
```
```   145                   UN_equiv_class2 [OF equiv_realrel equiv_realrel])
```
```   146 qed
```
```   147
```
```   148 lemma real_minus: "- Abs_Real(realrel``{(x,y)}) = Abs_Real(realrel `` {(y,x)})"
```
```   149 proof -
```
```   150   have "(\<lambda>(x,y). {Abs_Real (realrel``{(y,x)})}) respects realrel"
```
```   151     by (simp add: congruent_def add_commute)
```
```   152   thus ?thesis
```
```   153     by (simp add: real_minus_def UN_equiv_class [OF equiv_realrel])
```
```   154 qed
```
```   155
```
```   156 instance real :: ab_group_add
```
```   157 proof
```
```   158   fix x y z :: real
```
```   159   show "(x + y) + z = x + (y + z)"
```
```   160     by (cases x, cases y, cases z, simp add: real_add add_assoc)
```
```   161   show "x + y = y + x"
```
```   162     by (cases x, cases y, simp add: real_add add_commute)
```
```   163   show "0 + x = x"
```
```   164     by (cases x, simp add: real_add real_zero_def add_ac)
```
```   165   show "- x + x = 0"
```
```   166     by (cases x, simp add: real_minus real_add real_zero_def add_commute)
```
```   167   show "x - y = x + - y"
```
```   168     by (simp add: real_diff_def)
```
```   169 qed
```
```   170
```
```   171
```
```   172 subsection {* Multiplication *}
```
```   173
```
```   174 lemma real_mult_congruent2_lemma:
```
```   175      "!!(x1::preal). [| x1 + y2 = x2 + y1 |] ==>
```
```   176           x * x1 + y * y1 + (x * y2 + y * x2) =
```
```   177           x * x2 + y * y2 + (x * y1 + y * x1)"
```
```   178 apply (simp add: add_left_commute add_assoc [symmetric])
```
```   179 apply (simp add: add_assoc right_distrib [symmetric])
```
```   180 apply (simp add: add_commute)
```
```   181 done
```
```   182
```
```   183 lemma real_mult_congruent2:
```
```   184     "(%p1 p2.
```
```   185         (%(x1,y1). (%(x2,y2).
```
```   186           { Abs_Real (realrel``{(x1*x2 + y1*y2, x1*y2+y1*x2)}) }) p2) p1)
```
```   187      respects2 realrel"
```
```   188 apply (rule congruent2_commuteI [OF equiv_realrel], clarify)
```
```   189 apply (simp add: mult_commute add_commute)
```
```   190 apply (auto simp add: real_mult_congruent2_lemma)
```
```   191 done
```
```   192
```
```   193 lemma real_mult:
```
```   194       "Abs_Real((realrel``{(x1,y1)})) * Abs_Real((realrel``{(x2,y2)})) =
```
```   195        Abs_Real(realrel `` {(x1*x2+y1*y2,x1*y2+y1*x2)})"
```
```   196 by (simp add: real_mult_def UN_UN_split_split_eq
```
```   197          UN_equiv_class2 [OF equiv_realrel equiv_realrel real_mult_congruent2])
```
```   198
```
```   199 lemma real_mult_commute: "(z::real) * w = w * z"
```
```   200 by (cases z, cases w, simp add: real_mult add_ac mult_ac)
```
```   201
```
```   202 lemma real_mult_assoc: "((z1::real) * z2) * z3 = z1 * (z2 * z3)"
```
```   203 apply (cases z1, cases z2, cases z3)
```
```   204 apply (simp add: real_mult algebra_simps)
```
```   205 done
```
```   206
```
```   207 lemma real_mult_1: "(1::real) * z = z"
```
```   208 apply (cases z)
```
```   209 apply (simp add: real_mult real_one_def algebra_simps)
```
```   210 done
```
```   211
```
```   212 lemma real_add_mult_distrib: "((z1::real) + z2) * w = (z1 * w) + (z2 * w)"
```
```   213 apply (cases z1, cases z2, cases w)
```
```   214 apply (simp add: real_add real_mult algebra_simps)
```
```   215 done
```
```   216
```
```   217 text{*one and zero are distinct*}
```
```   218 lemma real_zero_not_eq_one: "0 \<noteq> (1::real)"
```
```   219 proof -
```
```   220   have "(1::preal) < 1 + 1"
```
```   221     by (simp add: preal_self_less_add_left)
```
```   222   thus ?thesis
```
```   223     by (simp add: real_zero_def real_one_def)
```
```   224 qed
```
```   225
```
```   226 instance real :: comm_ring_1
```
```   227 proof
```
```   228   fix x y z :: real
```
```   229   show "(x * y) * z = x * (y * z)" by (rule real_mult_assoc)
```
```   230   show "x * y = y * x" by (rule real_mult_commute)
```
```   231   show "1 * x = x" by (rule real_mult_1)
```
```   232   show "(x + y) * z = x * z + y * z" by (rule real_add_mult_distrib)
```
```   233   show "0 \<noteq> (1::real)" by (rule real_zero_not_eq_one)
```
```   234 qed
```
```   235
```
```   236 subsection {* Inverse and Division *}
```
```   237
```
```   238 lemma real_zero_iff: "Abs_Real (realrel `` {(x, x)}) = 0"
```
```   239 by (simp add: real_zero_def add_commute)
```
```   240
```
```   241 text{*Instead of using an existential quantifier and constructing the inverse
```
```   242 within the proof, we could define the inverse explicitly.*}
```
```   243
```
```   244 lemma real_mult_inverse_left_ex: "x \<noteq> 0 ==> \<exists>y. y*x = (1::real)"
```
```   245 apply (simp add: real_zero_def real_one_def, cases x)
```
```   246 apply (cut_tac x = xa and y = y in linorder_less_linear)
```
```   247 apply (auto dest!: less_add_left_Ex simp add: real_zero_iff)
```
```   248 apply (rule_tac
```
```   249         x = "Abs_Real (realrel``{(1, inverse (D) + 1)})"
```
```   250        in exI)
```
```   251 apply (rule_tac [2]
```
```   252         x = "Abs_Real (realrel``{(inverse (D) + 1, 1)})"
```
```   253        in exI)
```
```   254 apply (auto simp add: real_mult preal_mult_inverse_right algebra_simps)
```
```   255 done
```
```   256
```
```   257 lemma real_mult_inverse_left: "x \<noteq> 0 ==> inverse(x)*x = (1::real)"
```
```   258 apply (simp add: real_inverse_def)
```
```   259 apply (drule real_mult_inverse_left_ex, safe)
```
```   260 apply (rule theI, assumption, rename_tac z)
```
```   261 apply (subgoal_tac "(z * x) * y = z * (x * y)")
```
```   262 apply (simp add: mult_commute)
```
```   263 apply (rule mult_assoc)
```
```   264 done
```
```   265
```
```   266
```
```   267 subsection{*The Real Numbers form a Field*}
```
```   268
```
```   269 instance real :: field
```
```   270 proof
```
```   271   fix x y z :: real
```
```   272   show "x \<noteq> 0 ==> inverse x * x = 1" by (rule real_mult_inverse_left)
```
```   273   show "x / y = x * inverse y" by (simp add: real_divide_def)
```
```   274 qed
```
```   275
```
```   276
```
```   277 text{*Inverse of zero!  Useful to simplify certain equations*}
```
```   278
```
```   279 lemma INVERSE_ZERO: "inverse 0 = (0::real)"
```
```   280 by (simp add: real_inverse_def)
```
```   281
```
```   282 instance real :: division_by_zero
```
```   283 proof
```
```   284   show "inverse 0 = (0::real)" by (rule INVERSE_ZERO)
```
```   285 qed
```
```   286
```
```   287
```
```   288 subsection{*The @{text "\<le>"} Ordering*}
```
```   289
```
```   290 lemma real_le_refl: "w \<le> (w::real)"
```
```   291 by (cases w, force simp add: real_le_def)
```
```   292
```
```   293 text{*The arithmetic decision procedure is not set up for type preal.
```
```   294   This lemma is currently unused, but it could simplify the proofs of the
```
```   295   following two lemmas.*}
```
```   296 lemma preal_eq_le_imp_le:
```
```   297   assumes eq: "a+b = c+d" and le: "c \<le> a"
```
```   298   shows "b \<le> (d::preal)"
```
```   299 proof -
```
```   300   have "c+d \<le> a+d" by (simp add: prems)
```
```   301   hence "a+b \<le> a+d" by (simp add: prems)
```
```   302   thus "b \<le> d" by simp
```
```   303 qed
```
```   304
```
```   305 lemma real_le_lemma:
```
```   306   assumes l: "u1 + v2 \<le> u2 + v1"
```
```   307       and "x1 + v1 = u1 + y1"
```
```   308       and "x2 + v2 = u2 + y2"
```
```   309   shows "x1 + y2 \<le> x2 + (y1::preal)"
```
```   310 proof -
```
```   311   have "(x1+v1) + (u2+y2) = (u1+y1) + (x2+v2)" by (simp add: prems)
```
```   312   hence "(x1+y2) + (u2+v1) = (x2+y1) + (u1+v2)" by (simp add: add_ac)
```
```   313   also have "... \<le> (x2+y1) + (u2+v1)" by (simp add: prems)
```
```   314   finally show ?thesis by simp
```
```   315 qed
```
```   316
```
```   317 lemma real_le:
```
```   318      "(Abs_Real(realrel``{(x1,y1)}) \<le> Abs_Real(realrel``{(x2,y2)})) =
```
```   319       (x1 + y2 \<le> x2 + y1)"
```
```   320 apply (simp add: real_le_def)
```
```   321 apply (auto intro: real_le_lemma)
```
```   322 done
```
```   323
```
```   324 lemma real_le_anti_sym: "[| z \<le> w; w \<le> z |] ==> z = (w::real)"
```
```   325 by (cases z, cases w, simp add: real_le)
```
```   326
```
```   327 lemma real_trans_lemma:
```
```   328   assumes "x + v \<le> u + y"
```
```   329       and "u + v' \<le> u' + v"
```
```   330       and "x2 + v2 = u2 + y2"
```
```   331   shows "x + v' \<le> u' + (y::preal)"
```
```   332 proof -
```
```   333   have "(x+v') + (u+v) = (x+v) + (u+v')" by (simp add: add_ac)
```
```   334   also have "... \<le> (u+y) + (u+v')" by (simp add: prems)
```
```   335   also have "... \<le> (u+y) + (u'+v)" by (simp add: prems)
```
```   336   also have "... = (u'+y) + (u+v)"  by (simp add: add_ac)
```
```   337   finally show ?thesis by simp
```
```   338 qed
```
```   339
```
```   340 lemma real_le_trans: "[| i \<le> j; j \<le> k |] ==> i \<le> (k::real)"
```
```   341 apply (cases i, cases j, cases k)
```
```   342 apply (simp add: real_le)
```
```   343 apply (blast intro: real_trans_lemma)
```
```   344 done
```
```   345
```
```   346 instance real :: order
```
```   347 proof
```
```   348   fix u v :: real
```
```   349   show "u < v \<longleftrightarrow> u \<le> v \<and> \<not> v \<le> u"
```
```   350     by (auto simp add: real_less_def intro: real_le_anti_sym)
```
```   351 qed (assumption | rule real_le_refl real_le_trans real_le_anti_sym)+
```
```   352
```
```   353 (* Axiom 'linorder_linear' of class 'linorder': *)
```
```   354 lemma real_le_linear: "(z::real) \<le> w | w \<le> z"
```
```   355 apply (cases z, cases w)
```
```   356 apply (auto simp add: real_le real_zero_def add_ac)
```
```   357 done
```
```   358
```
```   359 instance real :: linorder
```
```   360   by (intro_classes, rule real_le_linear)
```
```   361
```
```   362
```
```   363 lemma real_le_eq_diff: "(x \<le> y) = (x-y \<le> (0::real))"
```
```   364 apply (cases x, cases y)
```
```   365 apply (auto simp add: real_le real_zero_def real_diff_def real_add real_minus
```
```   366                       add_ac)
```
```   367 apply (simp_all add: add_assoc [symmetric])
```
```   368 done
```
```   369
```
```   370 lemma real_add_left_mono:
```
```   371   assumes le: "x \<le> y" shows "z + x \<le> z + (y::real)"
```
```   372 proof -
```
```   373   have "z + x - (z + y) = (z + -z) + (x - y)"
```
```   374     by (simp add: algebra_simps)
```
```   375   with le show ?thesis
```
```   376     by (simp add: real_le_eq_diff[of x] real_le_eq_diff[of "z+x"] diff_minus)
```
```   377 qed
```
```   378
```
```   379 lemma real_sum_gt_zero_less: "(0 < S + (-W::real)) ==> (W < S)"
```
```   380 by (simp add: linorder_not_le [symmetric] real_le_eq_diff [of S] diff_minus)
```
```   381
```
```   382 lemma real_less_sum_gt_zero: "(W < S) ==> (0 < S + (-W::real))"
```
```   383 by (simp add: linorder_not_le [symmetric] real_le_eq_diff [of S] diff_minus)
```
```   384
```
```   385 lemma real_mult_order: "[| 0 < x; 0 < y |] ==> (0::real) < x * y"
```
```   386 apply (cases x, cases y)
```
```   387 apply (simp add: linorder_not_le [where 'a = real, symmetric]
```
```   388                  linorder_not_le [where 'a = preal]
```
```   389                   real_zero_def real_le real_mult)
```
```   390   --{*Reduce to the (simpler) @{text "\<le>"} relation *}
```
```   391 apply (auto dest!: less_add_left_Ex
```
```   392      simp add: algebra_simps preal_self_less_add_left)
```
```   393 done
```
```   394
```
```   395 lemma real_mult_less_mono2: "[| (0::real) < z; x < y |] ==> z * x < z * y"
```
```   396 apply (rule real_sum_gt_zero_less)
```
```   397 apply (drule real_less_sum_gt_zero [of x y])
```
```   398 apply (drule real_mult_order, assumption)
```
```   399 apply (simp add: right_distrib)
```
```   400 done
```
```   401
```
```   402 instantiation real :: distrib_lattice
```
```   403 begin
```
```   404
```
```   405 definition
```
```   406   "(inf \<Colon> real \<Rightarrow> real \<Rightarrow> real) = min"
```
```   407
```
```   408 definition
```
```   409   "(sup \<Colon> real \<Rightarrow> real \<Rightarrow> real) = max"
```
```   410
```
```   411 instance
```
```   412   by default (auto simp add: inf_real_def sup_real_def min_max.sup_inf_distrib1)
```
```   413
```
```   414 end
```
```   415
```
```   416
```
```   417 subsection{*The Reals Form an Ordered Field*}
```
```   418
```
```   419 instance real :: ordered_field
```
```   420 proof
```
```   421   fix x y z :: real
```
```   422   show "x \<le> y ==> z + x \<le> z + y" by (rule real_add_left_mono)
```
```   423   show "x < y ==> 0 < z ==> z * x < z * y" by (rule real_mult_less_mono2)
```
```   424   show "\<bar>x\<bar> = (if x < 0 then -x else x)" by (simp only: real_abs_def)
```
```   425   show "sgn x = (if x=0 then 0 else if 0<x then 1 else - 1)"
```
```   426     by (simp only: real_sgn_def)
```
```   427 qed
```
```   428
```
```   429 instance real :: lordered_ab_group_add ..
```
```   430
```
```   431 text{*The function @{term real_of_preal} requires many proofs, but it seems
```
```   432 to be essential for proving completeness of the reals from that of the
```
```   433 positive reals.*}
```
```   434
```
```   435 lemma real_of_preal_add:
```
```   436      "real_of_preal ((x::preal) + y) = real_of_preal x + real_of_preal y"
```
```   437 by (simp add: real_of_preal_def real_add algebra_simps)
```
```   438
```
```   439 lemma real_of_preal_mult:
```
```   440      "real_of_preal ((x::preal) * y) = real_of_preal x* real_of_preal y"
```
```   441 by (simp add: real_of_preal_def real_mult algebra_simps)
```
```   442
```
```   443
```
```   444 text{*Gleason prop 9-4.4 p 127*}
```
```   445 lemma real_of_preal_trichotomy:
```
```   446       "\<exists>m. (x::real) = real_of_preal m | x = 0 | x = -(real_of_preal m)"
```
```   447 apply (simp add: real_of_preal_def real_zero_def, cases x)
```
```   448 apply (auto simp add: real_minus add_ac)
```
```   449 apply (cut_tac x = x and y = y in linorder_less_linear)
```
```   450 apply (auto dest!: less_add_left_Ex simp add: add_assoc [symmetric])
```
```   451 done
```
```   452
```
```   453 lemma real_of_preal_leD:
```
```   454       "real_of_preal m1 \<le> real_of_preal m2 ==> m1 \<le> m2"
```
```   455 by (simp add: real_of_preal_def real_le)
```
```   456
```
```   457 lemma real_of_preal_lessI: "m1 < m2 ==> real_of_preal m1 < real_of_preal m2"
```
```   458 by (auto simp add: real_of_preal_leD linorder_not_le [symmetric])
```
```   459
```
```   460 lemma real_of_preal_lessD:
```
```   461       "real_of_preal m1 < real_of_preal m2 ==> m1 < m2"
```
```   462 by (simp add: real_of_preal_def real_le linorder_not_le [symmetric])
```
```   463
```
```   464 lemma real_of_preal_less_iff [simp]:
```
```   465      "(real_of_preal m1 < real_of_preal m2) = (m1 < m2)"
```
```   466 by (blast intro: real_of_preal_lessI real_of_preal_lessD)
```
```   467
```
```   468 lemma real_of_preal_le_iff:
```
```   469      "(real_of_preal m1 \<le> real_of_preal m2) = (m1 \<le> m2)"
```
```   470 by (simp add: linorder_not_less [symmetric])
```
```   471
```
```   472 lemma real_of_preal_zero_less: "0 < real_of_preal m"
```
```   473 apply (insert preal_self_less_add_left [of 1 m])
```
```   474 apply (auto simp add: real_zero_def real_of_preal_def
```
```   475                       real_less_def real_le_def add_ac)
```
```   476 apply (rule_tac x="m + 1" in exI, rule_tac x="1" in exI)
```
```   477 apply (simp add: add_ac)
```
```   478 done
```
```   479
```
```   480 lemma real_of_preal_minus_less_zero: "- real_of_preal m < 0"
```
```   481 by (simp add: real_of_preal_zero_less)
```
```   482
```
```   483 lemma real_of_preal_not_minus_gt_zero: "~ 0 < - real_of_preal m"
```
```   484 proof -
```
```   485   from real_of_preal_minus_less_zero
```
```   486   show ?thesis by (blast dest: order_less_trans)
```
```   487 qed
```
```   488
```
```   489
```
```   490 subsection{*Theorems About the Ordering*}
```
```   491
```
```   492 lemma real_gt_zero_preal_Ex: "(0 < x) = (\<exists>y. x = real_of_preal y)"
```
```   493 apply (auto simp add: real_of_preal_zero_less)
```
```   494 apply (cut_tac x = x in real_of_preal_trichotomy)
```
```   495 apply (blast elim!: real_of_preal_not_minus_gt_zero [THEN notE])
```
```   496 done
```
```   497
```
```   498 lemma real_gt_preal_preal_Ex:
```
```   499      "real_of_preal z < x ==> \<exists>y. x = real_of_preal y"
```
```   500 by (blast dest!: real_of_preal_zero_less [THEN order_less_trans]
```
```   501              intro: real_gt_zero_preal_Ex [THEN iffD1])
```
```   502
```
```   503 lemma real_ge_preal_preal_Ex:
```
```   504      "real_of_preal z \<le> x ==> \<exists>y. x = real_of_preal y"
```
```   505 by (blast dest: order_le_imp_less_or_eq real_gt_preal_preal_Ex)
```
```   506
```
```   507 lemma real_less_all_preal: "y \<le> 0 ==> \<forall>x. y < real_of_preal x"
```
```   508 by (auto elim: order_le_imp_less_or_eq [THEN disjE]
```
```   509             intro: real_of_preal_zero_less [THEN [2] order_less_trans]
```
```   510             simp add: real_of_preal_zero_less)
```
```   511
```
```   512 lemma real_less_all_real2: "~ 0 < y ==> \<forall>x. y < real_of_preal x"
```
```   513 by (blast intro!: real_less_all_preal linorder_not_less [THEN iffD1])
```
```   514
```
```   515
```
```   516 subsection{*More Lemmas*}
```
```   517
```
```   518 lemma real_mult_left_cancel: "(c::real) \<noteq> 0 ==> (c*a=c*b) = (a=b)"
```
```   519 by auto
```
```   520
```
```   521 lemma real_mult_right_cancel: "(c::real) \<noteq> 0 ==> (a*c=b*c) = (a=b)"
```
```   522 by auto
```
```   523
```
```   524 lemma real_mult_less_iff1 [simp]: "(0::real) < z ==> (x*z < y*z) = (x < y)"
```
```   525   by (force elim: order_less_asym
```
```   526             simp add: Ring_and_Field.mult_less_cancel_right)
```
```   527
```
```   528 lemma real_mult_le_cancel_iff1 [simp]: "(0::real) < z ==> (x*z \<le> y*z) = (x\<le>y)"
```
```   529 apply (simp add: mult_le_cancel_right)
```
```   530 apply (blast intro: elim: order_less_asym)
```
```   531 done
```
```   532
```
```   533 lemma real_mult_le_cancel_iff2 [simp]: "(0::real) < z ==> (z*x \<le> z*y) = (x\<le>y)"
```
```   534 by(simp add:mult_commute)
```
```   535
```
```   536 lemma real_inverse_gt_one: "[| (0::real) < x; x < 1 |] ==> 1 < inverse x"
```
```   537 by (simp add: one_less_inverse_iff) (* TODO: generalize/move *)
```
```   538
```
```   539
```
```   540 subsection {* Embedding numbers into the Reals *}
```
```   541
```
```   542 abbreviation
```
```   543   real_of_nat :: "nat \<Rightarrow> real"
```
```   544 where
```
```   545   "real_of_nat \<equiv> of_nat"
```
```   546
```
```   547 abbreviation
```
```   548   real_of_int :: "int \<Rightarrow> real"
```
```   549 where
```
```   550   "real_of_int \<equiv> of_int"
```
```   551
```
```   552 abbreviation
```
```   553   real_of_rat :: "rat \<Rightarrow> real"
```
```   554 where
```
```   555   "real_of_rat \<equiv> of_rat"
```
```   556
```
```   557 consts
```
```   558   (*overloaded constant for injecting other types into "real"*)
```
```   559   real :: "'a => real"
```
```   560
```
```   561 defs (overloaded)
```
```   562   real_of_nat_def [code unfold]: "real == real_of_nat"
```
```   563   real_of_int_def [code unfold]: "real == real_of_int"
```
```   564
```
```   565 lemma real_eq_of_nat: "real = of_nat"
```
```   566   unfolding real_of_nat_def ..
```
```   567
```
```   568 lemma real_eq_of_int: "real = of_int"
```
```   569   unfolding real_of_int_def ..
```
```   570
```
```   571 lemma real_of_int_zero [simp]: "real (0::int) = 0"
```
```   572 by (simp add: real_of_int_def)
```
```   573
```
```   574 lemma real_of_one [simp]: "real (1::int) = (1::real)"
```
```   575 by (simp add: real_of_int_def)
```
```   576
```
```   577 lemma real_of_int_add [simp]: "real(x + y) = real (x::int) + real y"
```
```   578 by (simp add: real_of_int_def)
```
```   579
```
```   580 lemma real_of_int_minus [simp]: "real(-x) = -real (x::int)"
```
```   581 by (simp add: real_of_int_def)
```
```   582
```
```   583 lemma real_of_int_diff [simp]: "real(x - y) = real (x::int) - real y"
```
```   584 by (simp add: real_of_int_def)
```
```   585
```
```   586 lemma real_of_int_mult [simp]: "real(x * y) = real (x::int) * real y"
```
```   587 by (simp add: real_of_int_def)
```
```   588
```
```   589 lemma real_of_int_setsum [simp]: "real ((SUM x:A. f x)::int) = (SUM x:A. real(f x))"
```
```   590   apply (subst real_eq_of_int)+
```
```   591   apply (rule of_int_setsum)
```
```   592 done
```
```   593
```
```   594 lemma real_of_int_setprod [simp]: "real ((PROD x:A. f x)::int) =
```
```   595     (PROD x:A. real(f x))"
```
```   596   apply (subst real_eq_of_int)+
```
```   597   apply (rule of_int_setprod)
```
```   598 done
```
```   599
```
```   600 lemma real_of_int_zero_cancel [simp, algebra, presburger]: "(real x = 0) = (x = (0::int))"
```
```   601 by (simp add: real_of_int_def)
```
```   602
```
```   603 lemma real_of_int_inject [iff, algebra, presburger]: "(real (x::int) = real y) = (x = y)"
```
```   604 by (simp add: real_of_int_def)
```
```   605
```
```   606 lemma real_of_int_less_iff [iff, presburger]: "(real (x::int) < real y) = (x < y)"
```
```   607 by (simp add: real_of_int_def)
```
```   608
```
```   609 lemma real_of_int_le_iff [simp, presburger]: "(real (x::int) \<le> real y) = (x \<le> y)"
```
```   610 by (simp add: real_of_int_def)
```
```   611
```
```   612 lemma real_of_int_gt_zero_cancel_iff [simp, presburger]: "(0 < real (n::int)) = (0 < n)"
```
```   613 by (simp add: real_of_int_def)
```
```   614
```
```   615 lemma real_of_int_ge_zero_cancel_iff [simp, presburger]: "(0 <= real (n::int)) = (0 <= n)"
```
```   616 by (simp add: real_of_int_def)
```
```   617
```
```   618 lemma real_of_int_lt_zero_cancel_iff [simp, presburger]: "(real (n::int) < 0) = (n < 0)"
```
```   619 by (simp add: real_of_int_def)
```
```   620
```
```   621 lemma real_of_int_le_zero_cancel_iff [simp, presburger]: "(real (n::int) <= 0) = (n <= 0)"
```
```   622 by (simp add: real_of_int_def)
```
```   623
```
```   624 lemma real_of_int_abs [simp]: "real (abs x) = abs(real (x::int))"
```
```   625 by (auto simp add: abs_if)
```
```   626
```
```   627 lemma int_less_real_le: "((n::int) < m) = (real n + 1 <= real m)"
```
```   628   apply (subgoal_tac "real n + 1 = real (n + 1)")
```
```   629   apply (simp del: real_of_int_add)
```
```   630   apply auto
```
```   631 done
```
```   632
```
```   633 lemma int_le_real_less: "((n::int) <= m) = (real n < real m + 1)"
```
```   634   apply (subgoal_tac "real m + 1 = real (m + 1)")
```
```   635   apply (simp del: real_of_int_add)
```
```   636   apply simp
```
```   637 done
```
```   638
```
```   639 lemma real_of_int_div_aux: "d ~= 0 ==> (real (x::int)) / (real d) =
```
```   640     real (x div d) + (real (x mod d)) / (real d)"
```
```   641 proof -
```
```   642   assume "d ~= 0"
```
```   643   have "x = (x div d) * d + x mod d"
```
```   644     by auto
```
```   645   then have "real x = real (x div d) * real d + real(x mod d)"
```
```   646     by (simp only: real_of_int_mult [THEN sym] real_of_int_add [THEN sym])
```
```   647   then have "real x / real d = ... / real d"
```
```   648     by simp
```
```   649   then show ?thesis
```
```   650     by (auto simp add: add_divide_distrib algebra_simps prems)
```
```   651 qed
```
```   652
```
```   653 lemma real_of_int_div: "(d::int) ~= 0 ==> d dvd n ==>
```
```   654     real(n div d) = real n / real d"
```
```   655   apply (frule real_of_int_div_aux [of d n])
```
```   656   apply simp
```
```   657   apply (simp add: dvd_eq_mod_eq_0)
```
```   658 done
```
```   659
```
```   660 lemma real_of_int_div2:
```
```   661   "0 <= real (n::int) / real (x) - real (n div x)"
```
```   662   apply (case_tac "x = 0")
```
```   663   apply simp
```
```   664   apply (case_tac "0 < x")
```
```   665   apply (simp add: algebra_simps)
```
```   666   apply (subst real_of_int_div_aux)
```
```   667   apply simp
```
```   668   apply simp
```
```   669   apply (subst zero_le_divide_iff)
```
```   670   apply auto
```
```   671   apply (simp add: algebra_simps)
```
```   672   apply (subst real_of_int_div_aux)
```
```   673   apply simp
```
```   674   apply simp
```
```   675   apply (subst zero_le_divide_iff)
```
```   676   apply auto
```
```   677 done
```
```   678
```
```   679 lemma real_of_int_div3:
```
```   680   "real (n::int) / real (x) - real (n div x) <= 1"
```
```   681   apply(case_tac "x = 0")
```
```   682   apply simp
```
```   683   apply (simp add: algebra_simps)
```
```   684   apply (subst real_of_int_div_aux)
```
```   685   apply assumption
```
```   686   apply simp
```
```   687   apply (subst divide_le_eq)
```
```   688   apply clarsimp
```
```   689   apply (rule conjI)
```
```   690   apply (rule impI)
```
```   691   apply (rule order_less_imp_le)
```
```   692   apply simp
```
```   693   apply (rule impI)
```
```   694   apply (rule order_less_imp_le)
```
```   695   apply simp
```
```   696 done
```
```   697
```
```   698 lemma real_of_int_div4: "real (n div x) <= real (n::int) / real x"
```
```   699 by (insert real_of_int_div2 [of n x], simp)
```
```   700
```
```   701
```
```   702 subsection{*Embedding the Naturals into the Reals*}
```
```   703
```
```   704 lemma real_of_nat_zero [simp]: "real (0::nat) = 0"
```
```   705 by (simp add: real_of_nat_def)
```
```   706
```
```   707 lemma real_of_nat_1 [simp]: "real (1::nat) = 1"
```
```   708 by (simp add: real_of_nat_def)
```
```   709
```
```   710 lemma real_of_nat_one [simp]: "real (Suc 0) = (1::real)"
```
```   711 by (simp add: real_of_nat_def)
```
```   712
```
```   713 lemma real_of_nat_add [simp]: "real (m + n) = real (m::nat) + real n"
```
```   714 by (simp add: real_of_nat_def)
```
```   715
```
```   716 (*Not for addsimps: often the LHS is used to represent a positive natural*)
```
```   717 lemma real_of_nat_Suc: "real (Suc n) = real n + (1::real)"
```
```   718 by (simp add: real_of_nat_def)
```
```   719
```
```   720 lemma real_of_nat_less_iff [iff]:
```
```   721      "(real (n::nat) < real m) = (n < m)"
```
```   722 by (simp add: real_of_nat_def)
```
```   723
```
```   724 lemma real_of_nat_le_iff [iff]: "(real (n::nat) \<le> real m) = (n \<le> m)"
```
```   725 by (simp add: real_of_nat_def)
```
```   726
```
```   727 lemma real_of_nat_ge_zero [iff]: "0 \<le> real (n::nat)"
```
```   728 by (simp add: real_of_nat_def zero_le_imp_of_nat)
```
```   729
```
```   730 lemma real_of_nat_Suc_gt_zero: "0 < real (Suc n)"
```
```   731 by (simp add: real_of_nat_def del: of_nat_Suc)
```
```   732
```
```   733 lemma real_of_nat_mult [simp]: "real (m * n) = real (m::nat) * real n"
```
```   734 by (simp add: real_of_nat_def of_nat_mult)
```
```   735
```
```   736 lemma real_of_nat_setsum [simp]: "real ((SUM x:A. f x)::nat) =
```
```   737     (SUM x:A. real(f x))"
```
```   738   apply (subst real_eq_of_nat)+
```
```   739   apply (rule of_nat_setsum)
```
```   740 done
```
```   741
```
```   742 lemma real_of_nat_setprod [simp]: "real ((PROD x:A. f x)::nat) =
```
```   743     (PROD x:A. real(f x))"
```
```   744   apply (subst real_eq_of_nat)+
```
```   745   apply (rule of_nat_setprod)
```
```   746 done
```
```   747
```
```   748 lemma real_of_card: "real (card A) = setsum (%x.1) A"
```
```   749   apply (subst card_eq_setsum)
```
```   750   apply (subst real_of_nat_setsum)
```
```   751   apply simp
```
```   752 done
```
```   753
```
```   754 lemma real_of_nat_inject [iff]: "(real (n::nat) = real m) = (n = m)"
```
```   755 by (simp add: real_of_nat_def)
```
```   756
```
```   757 lemma real_of_nat_zero_iff [iff]: "(real (n::nat) = 0) = (n = 0)"
```
```   758 by (simp add: real_of_nat_def)
```
```   759
```
```   760 lemma real_of_nat_diff: "n \<le> m ==> real (m - n) = real (m::nat) - real n"
```
```   761 by (simp add: add: real_of_nat_def of_nat_diff)
```
```   762
```
```   763 lemma real_of_nat_gt_zero_cancel_iff [simp]: "(0 < real (n::nat)) = (0 < n)"
```
```   764 by (auto simp: real_of_nat_def)
```
```   765
```
```   766 lemma real_of_nat_le_zero_cancel_iff [simp]: "(real (n::nat) \<le> 0) = (n = 0)"
```
```   767 by (simp add: add: real_of_nat_def)
```
```   768
```
```   769 lemma not_real_of_nat_less_zero [simp]: "~ real (n::nat) < 0"
```
```   770 by (simp add: add: real_of_nat_def)
```
```   771
```
```   772 lemma real_of_nat_ge_zero_cancel_iff [simp]: "(0 \<le> real (n::nat))"
```
```   773 by (simp add: add: real_of_nat_def)
```
```   774
```
```   775 lemma nat_less_real_le: "((n::nat) < m) = (real n + 1 <= real m)"
```
```   776   apply (subgoal_tac "real n + 1 = real (Suc n)")
```
```   777   apply simp
```
```   778   apply (auto simp add: real_of_nat_Suc)
```
```   779 done
```
```   780
```
```   781 lemma nat_le_real_less: "((n::nat) <= m) = (real n < real m + 1)"
```
```   782   apply (subgoal_tac "real m + 1 = real (Suc m)")
```
```   783   apply (simp add: less_Suc_eq_le)
```
```   784   apply (simp add: real_of_nat_Suc)
```
```   785 done
```
```   786
```
```   787 lemma real_of_nat_div_aux: "0 < d ==> (real (x::nat)) / (real d) =
```
```   788     real (x div d) + (real (x mod d)) / (real d)"
```
```   789 proof -
```
```   790   assume "0 < d"
```
```   791   have "x = (x div d) * d + x mod d"
```
```   792     by auto
```
```   793   then have "real x = real (x div d) * real d + real(x mod d)"
```
```   794     by (simp only: real_of_nat_mult [THEN sym] real_of_nat_add [THEN sym])
```
```   795   then have "real x / real d = \<dots> / real d"
```
```   796     by simp
```
```   797   then show ?thesis
```
```   798     by (auto simp add: add_divide_distrib algebra_simps prems)
```
```   799 qed
```
```   800
```
```   801 lemma real_of_nat_div: "0 < (d::nat) ==> d dvd n ==>
```
```   802     real(n div d) = real n / real d"
```
```   803   apply (frule real_of_nat_div_aux [of d n])
```
```   804   apply simp
```
```   805   apply (subst dvd_eq_mod_eq_0 [THEN sym])
```
```   806   apply assumption
```
```   807 done
```
```   808
```
```   809 lemma real_of_nat_div2:
```
```   810   "0 <= real (n::nat) / real (x) - real (n div x)"
```
```   811 apply(case_tac "x = 0")
```
```   812  apply (simp)
```
```   813 apply (simp add: algebra_simps)
```
```   814 apply (subst real_of_nat_div_aux)
```
```   815  apply simp
```
```   816 apply simp
```
```   817 apply (subst zero_le_divide_iff)
```
```   818 apply simp
```
```   819 done
```
```   820
```
```   821 lemma real_of_nat_div3:
```
```   822   "real (n::nat) / real (x) - real (n div x) <= 1"
```
```   823 apply(case_tac "x = 0")
```
```   824 apply (simp)
```
```   825 apply (simp add: algebra_simps)
```
```   826 apply (subst real_of_nat_div_aux)
```
```   827  apply simp
```
```   828 apply simp
```
```   829 done
```
```   830
```
```   831 lemma real_of_nat_div4: "real (n div x) <= real (n::nat) / real x"
```
```   832 by (insert real_of_nat_div2 [of n x], simp)
```
```   833
```
```   834 lemma real_of_int_real_of_nat: "real (int n) = real n"
```
```   835 by (simp add: real_of_nat_def real_of_int_def int_eq_of_nat)
```
```   836
```
```   837 lemma real_of_int_of_nat_eq [simp]: "real (of_nat n :: int) = real n"
```
```   838 by (simp add: real_of_int_def real_of_nat_def)
```
```   839
```
```   840 lemma real_nat_eq_real [simp]: "0 <= x ==> real(nat x) = real x"
```
```   841   apply (subgoal_tac "real(int(nat x)) = real(nat x)")
```
```   842   apply force
```
```   843   apply (simp only: real_of_int_real_of_nat)
```
```   844 done
```
```   845
```
```   846
```
```   847 subsection{* Rationals *}
```
```   848
```
```   849 lemma Rats_real_nat[simp]: "real(n::nat) \<in> \<rat>"
```
```   850 by (simp add: real_eq_of_nat)
```
```   851
```
```   852
```
```   853 lemma Rats_eq_int_div_int:
```
```   854   "\<rat> = { real(i::int)/real(j::int) |i j. j \<noteq> 0}" (is "_ = ?S")
```
```   855 proof
```
```   856   show "\<rat> \<subseteq> ?S"
```
```   857   proof
```
```   858     fix x::real assume "x : \<rat>"
```
```   859     then obtain r where "x = of_rat r" unfolding Rats_def ..
```
```   860     have "of_rat r : ?S"
```
```   861       by (cases r)(auto simp add:of_rat_rat real_eq_of_int)
```
```   862     thus "x : ?S" using `x = of_rat r` by simp
```
```   863   qed
```
```   864 next
```
```   865   show "?S \<subseteq> \<rat>"
```
```   866   proof(auto simp:Rats_def)
```
```   867     fix i j :: int assume "j \<noteq> 0"
```
```   868     hence "real i / real j = of_rat(Fract i j)"
```
```   869       by (simp add:of_rat_rat real_eq_of_int)
```
```   870     thus "real i / real j \<in> range of_rat" by blast
```
```   871   qed
```
```   872 qed
```
```   873
```
```   874 lemma Rats_eq_int_div_nat:
```
```   875   "\<rat> = { real(i::int)/real(n::nat) |i n. n \<noteq> 0}"
```
```   876 proof(auto simp:Rats_eq_int_div_int)
```
```   877   fix i j::int assume "j \<noteq> 0"
```
```   878   show "EX (i'::int) (n::nat). real i/real j = real i'/real n \<and> 0<n"
```
```   879   proof cases
```
```   880     assume "j>0"
```
```   881     hence "real i/real j = real i/real(nat j) \<and> 0<nat j"
```
```   882       by (simp add: real_eq_of_int real_eq_of_nat of_nat_nat)
```
```   883     thus ?thesis by blast
```
```   884   next
```
```   885     assume "~ j>0"
```
```   886     hence "real i/real j = real(-i)/real(nat(-j)) \<and> 0<nat(-j)" using `j\<noteq>0`
```
```   887       by (simp add: real_eq_of_int real_eq_of_nat of_nat_nat)
```
```   888     thus ?thesis by blast
```
```   889   qed
```
```   890 next
```
```   891   fix i::int and n::nat assume "0 < n"
```
```   892   hence "real i/real n = real i/real(int n) \<and> int n \<noteq> 0" by simp
```
```   893   thus "\<exists>(i'::int) j::int. real i/real n = real i'/real j \<and> j \<noteq> 0" by blast
```
```   894 qed
```
```   895
```
```   896 lemma Rats_abs_nat_div_natE:
```
```   897   assumes "x \<in> \<rat>"
```
```   898   obtains m n where "n \<noteq> 0" and "\<bar>x\<bar> = real m / real n" and "gcd m n = 1"
```
```   899 proof -
```
```   900   from `x \<in> \<rat>` obtain i::int and n::nat where "n \<noteq> 0" and "x = real i / real n"
```
```   901     by(auto simp add: Rats_eq_int_div_nat)
```
```   902   hence "\<bar>x\<bar> = real(nat(abs i)) / real n" by simp
```
```   903   then obtain m :: nat where x_rat: "\<bar>x\<bar> = real m / real n" by blast
```
```   904   let ?gcd = "gcd m n"
```
```   905   from `n\<noteq>0` have gcd: "?gcd \<noteq> 0" by (simp add: gcd_zero)
```
```   906   let ?k = "m div ?gcd"
```
```   907   let ?l = "n div ?gcd"
```
```   908   let ?gcd' = "gcd ?k ?l"
```
```   909   have "?gcd dvd m" .. then have gcd_k: "?gcd * ?k = m"
```
```   910     by (rule dvd_mult_div_cancel)
```
```   911   have "?gcd dvd n" .. then have gcd_l: "?gcd * ?l = n"
```
```   912     by (rule dvd_mult_div_cancel)
```
```   913   from `n\<noteq>0` and gcd_l have "?l \<noteq> 0" by (auto iff del: neq0_conv)
```
```   914   moreover
```
```   915   have "\<bar>x\<bar> = real ?k / real ?l"
```
```   916   proof -
```
```   917     from gcd have "real ?k / real ?l =
```
```   918         real (?gcd * ?k) / real (?gcd * ?l)" by simp
```
```   919     also from gcd_k and gcd_l have "\<dots> = real m / real n" by simp
```
```   920     also from x_rat have "\<dots> = \<bar>x\<bar>" ..
```
```   921     finally show ?thesis ..
```
```   922   qed
```
```   923   moreover
```
```   924   have "?gcd' = 1"
```
```   925   proof -
```
```   926     have "?gcd * ?gcd' = gcd (?gcd * ?k) (?gcd * ?l)"
```
```   927       by (rule gcd_mult_distrib2)
```
```   928     with gcd_k gcd_l have "?gcd * ?gcd' = ?gcd" by simp
```
```   929     with gcd show ?thesis by simp
```
```   930   qed
```
```   931   ultimately show ?thesis ..
```
```   932 qed
```
```   933
```
```   934
```
```   935 subsection{*Numerals and Arithmetic*}
```
```   936
```
```   937 instantiation real :: number_ring
```
```   938 begin
```
```   939
```
```   940 definition
```
```   941   real_number_of_def [code del]: "number_of w = real_of_int w"
```
```   942
```
```   943 instance
```
```   944   by intro_classes (simp add: real_number_of_def)
```
```   945
```
```   946 end
```
```   947
```
```   948 lemma [code unfold, symmetric, code post]:
```
```   949   "number_of k = real_of_int (number_of k)"
```
```   950   unfolding number_of_is_id real_number_of_def ..
```
```   951
```
```   952
```
```   953 text{*Collapse applications of @{term real} to @{term number_of}*}
```
```   954 lemma real_number_of [simp]: "real (number_of v :: int) = number_of v"
```
```   955 by (simp add:  real_of_int_def of_int_number_of_eq)
```
```   956
```
```   957 lemma real_of_nat_number_of [simp]:
```
```   958      "real (number_of v :: nat) =
```
```   959         (if neg (number_of v :: int) then 0
```
```   960          else (number_of v :: real))"
```
```   961 by (simp add: real_of_int_real_of_nat [symmetric] int_nat_number_of)
```
```   962
```
```   963 declaration {*
```
```   964   K (Lin_Arith.add_inj_thms [@{thm real_of_nat_le_iff} RS iffD2, @{thm real_of_nat_inject} RS iffD2]
```
```   965     (* not needed because x < (y::nat) can be rewritten as Suc x <= y: real_of_nat_less_iff RS iffD2 *)
```
```   966   #> Lin_Arith.add_inj_thms [@{thm real_of_int_le_iff} RS iffD2, @{thm real_of_int_inject} RS iffD2]
```
```   967     (* not needed because x < (y::int) can be rewritten as x + 1 <= y: real_of_int_less_iff RS iffD2 *)
```
```   968   #> Lin_Arith.add_simps [@{thm real_of_nat_zero}, @{thm real_of_nat_Suc}, @{thm real_of_nat_add},
```
```   969       @{thm real_of_nat_mult}, @{thm real_of_int_zero}, @{thm real_of_one},
```
```   970       @{thm real_of_int_add}, @{thm real_of_int_minus}, @{thm real_of_int_diff},
```
```   971       @{thm real_of_int_mult}, @{thm real_of_int_of_nat_eq},
```
```   972       @{thm real_of_nat_number_of}, @{thm real_number_of}]
```
```   973   #> Lin_Arith.add_inj_const (@{const_name real}, HOLogic.natT --> HOLogic.realT)
```
```   974   #> Lin_Arith.add_inj_const (@{const_name real}, HOLogic.intT --> HOLogic.realT))
```
```   975 *}
```
```   976
```
```   977
```
```   978 subsection{* Simprules combining x+y and 0: ARE THEY NEEDED?*}
```
```   979
```
```   980 text{*Needed in this non-standard form by Hyperreal/Transcendental*}
```
```   981 lemma real_0_le_divide_iff:
```
```   982      "((0::real) \<le> x/y) = ((x \<le> 0 | 0 \<le> y) & (0 \<le> x | y \<le> 0))"
```
```   983 by (simp add: real_divide_def zero_le_mult_iff, auto)
```
```   984
```
```   985 lemma real_add_minus_iff [simp]: "(x + - a = (0::real)) = (x=a)"
```
```   986 by arith
```
```   987
```
```   988 lemma real_add_eq_0_iff: "(x+y = (0::real)) = (y = -x)"
```
```   989 by auto
```
```   990
```
```   991 lemma real_add_less_0_iff: "(x+y < (0::real)) = (y < -x)"
```
```   992 by auto
```
```   993
```
```   994 lemma real_0_less_add_iff: "((0::real) < x+y) = (-x < y)"
```
```   995 by auto
```
```   996
```
```   997 lemma real_add_le_0_iff: "(x+y \<le> (0::real)) = (y \<le> -x)"
```
```   998 by auto
```
```   999
```
```  1000 lemma real_0_le_add_iff: "((0::real) \<le> x+y) = (-x \<le> y)"
```
```  1001 by auto
```
```  1002
```
```  1003
```
```  1004 (*
```
```  1005 FIXME: we should have this, as for type int, but many proofs would break.
```
```  1006 It replaces x+-y by x-y.
```
```  1007 declare real_diff_def [symmetric, simp]
```
```  1008 *)
```
```  1009
```
```  1010 subsubsection{*Density of the Reals*}
```
```  1011
```
```  1012 lemma real_lbound_gt_zero:
```
```  1013      "[| (0::real) < d1; 0 < d2 |] ==> \<exists>e. 0 < e & e < d1 & e < d2"
```
```  1014 apply (rule_tac x = " (min d1 d2) /2" in exI)
```
```  1015 apply (simp add: min_def)
```
```  1016 done
```
```  1017
```
```  1018
```
```  1019 text{*Similar results are proved in @{text Ring_and_Field}*}
```
```  1020 lemma real_less_half_sum: "x < y ==> x < (x+y) / (2::real)"
```
```  1021   by auto
```
```  1022
```
```  1023 lemma real_gt_half_sum: "x < y ==> (x+y)/(2::real) < y"
```
```  1024   by auto
```
```  1025
```
```  1026
```
```  1027 subsection{*Absolute Value Function for the Reals*}
```
```  1028
```
```  1029 lemma abs_minus_add_cancel: "abs(x + (-y)) = abs (y + (-(x::real)))"
```
```  1030 by (simp add: abs_if)
```
```  1031
```
```  1032 (* FIXME: redundant, but used by Integration/RealRandVar.thy in AFP *)
```
```  1033 lemma abs_le_interval_iff: "(abs x \<le> r) = (-r\<le>x & x\<le>(r::real))"
```
```  1034 by (force simp add: OrderedGroup.abs_le_iff)
```
```  1035
```
```  1036 lemma abs_add_one_gt_zero [simp]: "(0::real) < 1 + abs(x)"
```
```  1037 by (simp add: abs_if)
```
```  1038
```
```  1039 lemma abs_real_of_nat_cancel [simp]: "abs (real x) = real (x::nat)"
```
```  1040 by (rule abs_of_nonneg [OF real_of_nat_ge_zero])
```
```  1041
```
```  1042 lemma abs_add_one_not_less_self [simp]: "~ abs(x) + (1::real) < x"
```
```  1043 by simp
```
```  1044
```
```  1045 lemma abs_sum_triangle_ineq: "abs ((x::real) + y + (-l + -m)) \<le> abs(x + -l) + abs(y + -m)"
```
```  1046 by simp
```
```  1047
```
```  1048 instance real :: lordered_ring
```
```  1049 proof
```
```  1050   fix a::real
```
```  1051   show "abs a = sup a (-a)"
```
```  1052     by (auto simp add: real_abs_def sup_real_def)
```
```  1053 qed
```
```  1054
```
```  1055
```
```  1056 subsection {* Implementation of rational real numbers *}
```
```  1057
```
```  1058 definition Ratreal :: "rat \<Rightarrow> real" where
```
```  1059   [simp]: "Ratreal = of_rat"
```
```  1060
```
```  1061 code_datatype Ratreal
```
```  1062
```
```  1063 lemma Ratreal_number_collapse [code post]:
```
```  1064   "Ratreal 0 = 0"
```
```  1065   "Ratreal 1 = 1"
```
```  1066   "Ratreal (number_of k) = number_of k"
```
```  1067 by simp_all
```
```  1068
```
```  1069 lemma zero_real_code [code, code unfold]:
```
```  1070   "0 = Ratreal 0"
```
```  1071 by simp
```
```  1072
```
```  1073 lemma one_real_code [code, code unfold]:
```
```  1074   "1 = Ratreal 1"
```
```  1075 by simp
```
```  1076
```
```  1077 lemma number_of_real_code [code unfold]:
```
```  1078   "number_of k = Ratreal (number_of k)"
```
```  1079 by simp
```
```  1080
```
```  1081 lemma Ratreal_number_of_quotient [code post]:
```
```  1082   "Ratreal (number_of r) / Ratreal (number_of s) = number_of r / number_of s"
```
```  1083 by simp
```
```  1084
```
```  1085 lemma Ratreal_number_of_quotient2 [code post]:
```
```  1086   "Ratreal (number_of r / number_of s) = number_of r / number_of s"
```
```  1087 unfolding Ratreal_number_of_quotient [symmetric] Ratreal_def of_rat_divide ..
```
```  1088
```
```  1089 instantiation real :: eq
```
```  1090 begin
```
```  1091
```
```  1092 definition "eq_class.eq (x\<Colon>real) y \<longleftrightarrow> x - y = 0"
```
```  1093
```
```  1094 instance by default (simp add: eq_real_def)
```
```  1095
```
```  1096 lemma real_eq_code [code]: "eq_class.eq (Ratreal x) (Ratreal y) \<longleftrightarrow> eq_class.eq x y"
```
```  1097   by (simp add: eq_real_def eq)
```
```  1098
```
```  1099 lemma real_eq_refl [code nbe]:
```
```  1100   "eq_class.eq (x::real) x \<longleftrightarrow> True"
```
```  1101   by (rule HOL.eq_refl)
```
```  1102
```
```  1103 end
```
```  1104
```
```  1105 lemma real_less_eq_code [code]: "Ratreal x \<le> Ratreal y \<longleftrightarrow> x \<le> y"
```
```  1106   by (simp add: of_rat_less_eq)
```
```  1107
```
```  1108 lemma real_less_code [code]: "Ratreal x < Ratreal y \<longleftrightarrow> x < y"
```
```  1109   by (simp add: of_rat_less)
```
```  1110
```
```  1111 lemma real_plus_code [code]: "Ratreal x + Ratreal y = Ratreal (x + y)"
```
```  1112   by (simp add: of_rat_add)
```
```  1113
```
```  1114 lemma real_times_code [code]: "Ratreal x * Ratreal y = Ratreal (x * y)"
```
```  1115   by (simp add: of_rat_mult)
```
```  1116
```
```  1117 lemma real_uminus_code [code]: "- Ratreal x = Ratreal (- x)"
```
```  1118   by (simp add: of_rat_minus)
```
```  1119
```
```  1120 lemma real_minus_code [code]: "Ratreal x - Ratreal y = Ratreal (x - y)"
```
```  1121   by (simp add: of_rat_diff)
```
```  1122
```
```  1123 lemma real_inverse_code [code]: "inverse (Ratreal x) = Ratreal (inverse x)"
```
```  1124   by (simp add: of_rat_inverse)
```
```  1125
```
```  1126 lemma real_divide_code [code]: "Ratreal x / Ratreal y = Ratreal (x / y)"
```
```  1127   by (simp add: of_rat_divide)
```
```  1128
```
```  1129 text {* Setup for SML code generator *}
```
```  1130
```
```  1131 types_code
```
```  1132   real ("(int */ int)")
```
```  1133 attach (term_of) {*
```
```  1134 fun term_of_real (p, q) =
```
```  1135   let
```
```  1136     val rT = HOLogic.realT
```
```  1137   in
```
```  1138     if q = 1 orelse p = 0 then HOLogic.mk_number rT p
```
```  1139     else @{term "op / \<Colon> real \<Rightarrow> real \<Rightarrow> real"} \$
```
```  1140       HOLogic.mk_number rT p \$ HOLogic.mk_number rT q
```
```  1141   end;
```
```  1142 *}
```
```  1143 attach (test) {*
```
```  1144 fun gen_real i =
```
```  1145   let
```
```  1146     val p = random_range 0 i;
```
```  1147     val q = random_range 1 (i + 1);
```
```  1148     val g = Integer.gcd p q;
```
```  1149     val p' = p div g;
```
```  1150     val q' = q div g;
```
```  1151     val r = (if one_of [true, false] then p' else ~ p',
```
```  1152       if p' = 0 then 0 else q')
```
```  1153   in
```
```  1154     (r, fn () => term_of_real r)
```
```  1155   end;
```
```  1156 *}
```
```  1157
```
```  1158 consts_code
```
```  1159   Ratreal ("(_)")
```
```  1160
```
```  1161 consts_code
```
```  1162   "of_int :: int \<Rightarrow> real" ("\<module>real'_of'_int")
```
```  1163 attach {*
```
```  1164 fun real_of_int 0 = (0, 0)
```
```  1165   | real_of_int i = (i, 1);
```
```  1166 *}
```
```  1167
```
```  1168 end
```