generalize some theorems about div/mod
authorhuffman
Tue, 27 Mar 2012 15:27:49 +0200
changeset 47159 978c00c20a59
parent 47142 d64fa2ca54b8
child 47160 8ada79014cb2
generalize some theorems about div/mod
NEWS
src/HOL/Divides.thy
src/HOL/Groebner_Basis.thy
src/HOL/Import/HOL_Light/HOLLightInt.thy
src/HOL/Library/Char_nat.thy
src/HOL/Library/Target_Numeral.thy
src/HOL/Numeral_Simprocs.thy
--- a/NEWS	Tue Mar 27 14:49:56 2012 +0200
+++ b/NEWS	Tue Mar 27 15:27:49 2012 +0200
@@ -145,6 +145,12 @@
   zdiv_zero ~> div_0
   zmod_zero ~> mod_0
   zmod_zdiv_trivial ~> mod_div_trivial
+  zdiv_zminus_zminus ~> div_minus_minus
+  zmod_zminus_zminus ~> mod_minus_minus
+  zdiv_zminus2 ~> div_minus_right
+  zmod_zminus2 ~> mod_minus_right
+  mod_mult_distrib ~> mult_mod_left
+  mod_mult_distrib2 ~> mult_mod_right
 
 * More default pred/set conversions on a couple of relation operations
 and predicates.  Consolidation of some relation theorems:
--- a/src/HOL/Divides.thy	Tue Mar 27 14:49:56 2012 +0200
+++ b/src/HOL/Divides.thy	Tue Mar 27 15:27:49 2012 +0200
@@ -343,6 +343,12 @@
   "(a * c) mod (b * c) = (a mod b) * c"
   using mod_mult_mult1 [of c a b] by (simp add: mult_commute)
 
+lemma mult_mod_left: "(a mod b) * c = (a * c) mod (b * c)"
+  by (fact mod_mult_mult2 [symmetric])
+
+lemma mult_mod_right: "c * (a mod b) = (c * a) mod (c * b)"
+  by (fact mod_mult_mult1 [symmetric])
+
 lemma dvd_mod: "k dvd m \<Longrightarrow> k dvd n \<Longrightarrow> k dvd (m mod n)"
   unfolding dvd_def by (auto simp add: mod_mult_mult1)
 
@@ -444,6 +450,19 @@
 apply simp
 done
 
+lemma div_minus_minus [simp]: "(-a) div (-b) = a div b"
+  using div_mult_mult1 [of "- 1" a b]
+  unfolding neg_equal_0_iff_equal by simp
+
+lemma mod_minus_minus [simp]: "(-a) mod (-b) = - (a mod b)"
+  using mod_mult_mult1 [of "- 1" a b] by simp
+
+lemma div_minus_right: "a div (-b) = (-a) div b"
+  using div_minus_minus [of "-a" b] by simp
+
+lemma mod_minus_right: "a mod (-b) = - ((-a) mod b)"
+  using mod_minus_minus [of "-a" b] by simp
+
 end
 
 
@@ -712,12 +731,6 @@
 lemma mod_1 [simp]: "m mod Suc 0 = 0"
 by (induct m) (simp_all add: mod_geq)
 
-lemma mod_mult_distrib: "(m mod n) * (k\<Colon>nat) = (m * k) mod (n * k)"
-  by (fact mod_mult_mult2 [symmetric]) (* FIXME: generalize *)
-
-lemma mod_mult_distrib2: "(k::nat) * (m mod n) = (k*m) mod (k*n)"
-  by (fact mod_mult_mult1 [symmetric]) (* FIXME: generalize *)
-
 (* a simple rearrangement of mod_div_equality: *)
 lemma mult_div_cancel: "(n::nat) * (m div n) = m - (m mod n)"
   using mod_div_equality2 [of n m] by arith
@@ -1489,15 +1502,6 @@
 text{*There is no @{text mod_neg_pos_trivial}.*}
 
 
-(*Simpler laws such as -a div b = -(a div b) FAIL, but see just below*)
-lemma zdiv_zminus_zminus [simp]: "(-a) div (-b) = a div (b::int)"
-  using div_mult_mult1 [of "-1" a b] by simp (* FIXME: generalize *)
-
-(*Simpler laws such as -a mod b = -(a mod b) FAIL, but see just below*)
-lemma zmod_zminus_zminus [simp]: "(-a) mod (-b) = - (a mod (b::int))"
-  using mod_mult_mult1 [of "-1" a b] by simp (* FIXME: generalize *)
-
-
 subsubsection {* Laws for div and mod with Unary Minus *}
 
 lemma zminus1_lemma:
@@ -1524,21 +1528,15 @@
   shows "- k mod l \<noteq> 0 \<Longrightarrow> k mod l \<noteq> 0"
   unfolding zmod_zminus1_eq_if by auto
 
-lemma zdiv_zminus2: "a div (-b) = (-a::int) div b"
-  using zdiv_zminus_zminus [of "-a" b] by simp (* FIXME: generalize *)
-
-lemma zmod_zminus2: "a mod (-b) = - ((-a::int) mod b)"
-  using zmod_zminus_zminus [of "-a" b] by simp (* FIXME: generalize*)
-
 lemma zdiv_zminus2_eq_if:
      "b \<noteq> (0::int)  
       ==> a div (-b) =  
           (if a mod b = 0 then - (a div b) else  - (a div b) - 1)"
-by (simp add: zdiv_zminus1_eq_if zdiv_zminus2)
+by (simp add: zdiv_zminus1_eq_if div_minus_right)
 
 lemma zmod_zminus2_eq_if:
      "a mod (-b::int) = (if a mod b = 0 then 0 else  (a mod b) - b)"
-by (simp add: zmod_zminus1_eq_if zmod_zminus2)
+by (simp add: zmod_zminus1_eq_if mod_minus_right)
 
 lemma zmod_zminus2_not_zero:
   fixes k l :: int
@@ -2024,7 +2022,7 @@
   have "(1 + 2 * (-b - 1)) div (2 * (-a)) = (-b - 1) div (-a)"
     by (rule pos_zdiv_mult_2, simp add: A)
   thus ?thesis
-    by (simp only: R zdiv_zminus_zminus diff_minus
+    by (simp only: R div_minus_minus diff_minus
       minus_add_distrib [symmetric] mult_minus_right)
 qed
 
@@ -2072,7 +2070,7 @@
   from assms have "0 \<le> - a" by auto
   then have "(1 + 2 * (- b - 1)) mod (2 * (- a)) = 1 + 2 * ((- b - 1) mod (- a))"
     by (rule pos_zmod_mult_2)
-  then show ?thesis by (simp add: zmod_zminus2 algebra_simps)
+  then show ?thesis by (simp add: mod_minus_right algebra_simps)
      (simp add: diff_minus add_ac)
 qed
 
@@ -2131,7 +2129,7 @@
 
 lemma neg_imp_zdiv_nonneg_iff:
   "b < (0::int) ==> (0 \<le> a div b) = (a \<le> (0::int))"
-apply (subst zdiv_zminus_zminus [symmetric])
+apply (subst div_minus_minus [symmetric])
 apply (subst pos_imp_zdiv_nonneg_iff, auto)
 done
 
--- a/src/HOL/Groebner_Basis.thy	Tue Mar 27 14:49:56 2012 +0200
+++ b/src/HOL/Groebner_Basis.thy	Tue Mar 27 15:27:49 2012 +0200
@@ -54,10 +54,10 @@
 declare mod_by_0[algebra]
 declare zmod_zdiv_equality[symmetric,algebra]
 declare zdiv_zmod_equality[symmetric, algebra]
-declare zdiv_zminus_zminus[algebra]
-declare zmod_zminus_zminus[algebra]
-declare zdiv_zminus2[algebra]
-declare zmod_zminus2[algebra]
+declare div_minus_minus[algebra]
+declare mod_minus_minus[algebra]
+declare div_minus_right[algebra]
+declare mod_minus_right[algebra]
 declare div_0[algebra]
 declare mod_0[algebra]
 declare mod_by_1[algebra]
--- a/src/HOL/Import/HOL_Light/HOLLightInt.thy	Tue Mar 27 14:49:56 2012 +0200
+++ b/src/HOL/Import/HOL_Light/HOLLightInt.thy	Tue Mar 27 15:27:49 2012 +0200
@@ -162,7 +162,7 @@
   apply (simp add: hl_mod_def hl_div_def)
   apply (metis comm_semiring_1_class.normalizing_semiring_rules(24) div_mult_self2 not_less_iff_gr_or_eq order_less_le add_0 zdiv_eq_0_iff mult_commute)
   apply (simp add: hl_mod_def hl_div_def)
-  by (metis add.comm_neutral add_pos_nonneg div_mult_self1 less_minus_iff minus_add minus_add_cancel minus_minus mult_zero_right not_square_less_zero zdiv_eq_0_iff zdiv_zminus2)
+  by (metis add.comm_neutral add_pos_nonneg div_mult_self1 less_minus_iff minus_add minus_add_cancel minus_minus mult_zero_right not_square_less_zero zdiv_eq_0_iff div_minus_right)
 
 lemma DEF_rem:
   "hl_mod = (SOME r. \<forall>m n. if n = int 0 then
@@ -182,7 +182,7 @@
   apply (simp add: hl_mod_def hl_div_def)
   apply (metis add_left_cancel mod_div_equality)
   apply (simp add: hl_mod_def hl_div_def)
-  by (metis minus_mult_right mod_mult_self2 mod_pos_pos_trivial add_commute zminus_zmod zmod_zminus2 mult_commute)
+  by (metis minus_mult_right mod_mult_self2 mod_pos_pos_trivial add_commute zminus_zmod mod_minus_right mult_commute)
 
 lemma DEF_int_gcd:
   "int_gcd = (SOME d. \<forall>a b. (int 0) \<le> (d (a, b)) \<and> (d (a, b)) dvd a \<and>
--- a/src/HOL/Library/Char_nat.thy	Tue Mar 27 14:49:56 2012 +0200
+++ b/src/HOL/Library/Char_nat.thy	Tue Mar 27 15:27:49 2012 +0200
@@ -158,7 +158,7 @@
     unfolding 256 mult_assoc [symmetric] mod_mult_self3 ..
   show ?thesis
     by (simp add: nat_of_char.simps char_of_nat_def nibble_of_pair
-      nat_of_nibble_of_nat mod_mult_distrib
+      nat_of_nibble_of_nat mult_mod_left
       n aux3 l_256 aux4 mod_add_eq [of "256 * k"] l_div_256)
 qed
 
--- a/src/HOL/Library/Target_Numeral.thy	Tue Mar 27 14:49:56 2012 +0200
+++ b/src/HOL/Library/Target_Numeral.thy	Tue Mar 27 15:27:49 2012 +0200
@@ -296,7 +296,7 @@
   have aux2: "\<And>q::int. - int_of k = int_of l * q \<longleftrightarrow> int_of k = int_of l * - q" by auto
   show ?thesis
     by (simp add: prod_eq_iff Target_Numeral.int_eq_iff prod_case_beta aux1)
-      (auto simp add: zdiv_zminus1_eq_if zmod_zminus1_eq_if zdiv_zminus2 zmod_zminus2 aux2)
+      (auto simp add: zdiv_zminus1_eq_if zmod_zminus1_eq_if div_minus_right mod_minus_right aux2)
 qed
 
 lemma div_int_code [code]:
--- a/src/HOL/Numeral_Simprocs.thy	Tue Mar 27 14:49:56 2012 +0200
+++ b/src/HOL/Numeral_Simprocs.thy	Tue Mar 27 15:27:49 2012 +0200
@@ -72,7 +72,7 @@
 
 lemma nat_mult_dvd_cancel_disj[simp]:
   "(k*m) dvd (k*n) = (k=0 | m dvd (n::nat))"
-by(auto simp: dvd_eq_mod_eq_0 mod_mult_distrib2[symmetric])
+by (auto simp: dvd_eq_mod_eq_0 mod_mult_mult1)
 
 lemma nat_mult_dvd_cancel1: "0 < k \<Longrightarrow> (k*m) dvd (k*n::nat) = (m dvd n)"
 by(auto)