--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/HOL/NatSimprocs.thy Thu May 31 18:16:52 2007 +0200
@@ -0,0 +1,391 @@
+(* Title: HOL/NatSimprocs.thy
+ ID: $Id$
+ Copyright 2003 TU Muenchen
+*)
+
+header {*Simprocs for the Naturals*}
+
+theory NatSimprocs
+imports NatBin
+uses "int_factor_simprocs.ML" "nat_simprocs.ML"
+begin
+
+setup nat_simprocs_setup
+
+subsection{*For simplifying @{term "Suc m - K"} and @{term "K - Suc m"}*}
+
+text{*Where K above is a literal*}
+
+lemma Suc_diff_eq_diff_pred: "Numeral0 < n ==> Suc m - n = m - (n - Numeral1)"
+by (simp add: numeral_0_eq_0 numeral_1_eq_1 split add: nat_diff_split)
+
+text {*Now just instantiating @{text n} to @{text "number_of v"} does
+ the right simplification, but with some redundant inequality
+ tests.*}
+lemma neg_number_of_pred_iff_0:
+ "neg (number_of (Numeral.pred v)::int) = (number_of v = (0::nat))"
+apply (subgoal_tac "neg (number_of (Numeral.pred v)) = (number_of v < Suc 0) ")
+apply (simp only: less_Suc_eq_le le_0_eq)
+apply (subst less_number_of_Suc, simp)
+done
+
+text{*No longer required as a simprule because of the @{text inverse_fold}
+ simproc*}
+lemma Suc_diff_number_of:
+ "neg (number_of (uminus v)::int) ==>
+ Suc m - (number_of v) = m - (number_of (Numeral.pred v))"
+apply (subst Suc_diff_eq_diff_pred)
+apply simp
+apply (simp del: nat_numeral_1_eq_1)
+apply (auto simp only: diff_nat_number_of less_0_number_of [symmetric]
+ neg_number_of_pred_iff_0)
+done
+
+lemma diff_Suc_eq_diff_pred: "m - Suc n = (m - 1) - n"
+by (simp add: numerals split add: nat_diff_split)
+
+
+subsection{*For @{term nat_case} and @{term nat_rec}*}
+
+lemma nat_case_number_of [simp]:
+ "nat_case a f (number_of v) =
+ (let pv = number_of (Numeral.pred v) in
+ if neg pv then a else f (nat pv))"
+by (simp split add: nat.split add: Let_def neg_number_of_pred_iff_0)
+
+lemma nat_case_add_eq_if [simp]:
+ "nat_case a f ((number_of v) + n) =
+ (let pv = number_of (Numeral.pred v) in
+ if neg pv then nat_case a f n else f (nat pv + n))"
+apply (subst add_eq_if)
+apply (simp split add: nat.split
+ del: nat_numeral_1_eq_1
+ add: numeral_1_eq_Suc_0 [symmetric] Let_def
+ neg_imp_number_of_eq_0 neg_number_of_pred_iff_0)
+done
+
+lemma nat_rec_number_of [simp]:
+ "nat_rec a f (number_of v) =
+ (let pv = number_of (Numeral.pred v) in
+ if neg pv then a else f (nat pv) (nat_rec a f (nat pv)))"
+apply (case_tac " (number_of v) ::nat")
+apply (simp_all (no_asm_simp) add: Let_def neg_number_of_pred_iff_0)
+apply (simp split add: split_if_asm)
+done
+
+lemma nat_rec_add_eq_if [simp]:
+ "nat_rec a f (number_of v + n) =
+ (let pv = number_of (Numeral.pred v) in
+ if neg pv then nat_rec a f n
+ else f (nat pv + n) (nat_rec a f (nat pv + n)))"
+apply (subst add_eq_if)
+apply (simp split add: nat.split
+ del: nat_numeral_1_eq_1
+ add: numeral_1_eq_Suc_0 [symmetric] Let_def neg_imp_number_of_eq_0
+ neg_number_of_pred_iff_0)
+done
+
+
+subsection{*Various Other Lemmas*}
+
+subsubsection{*Evens and Odds, for Mutilated Chess Board*}
+
+text{*Lemmas for specialist use, NOT as default simprules*}
+lemma nat_mult_2: "2 * z = (z+z::nat)"
+proof -
+ have "2*z = (1 + 1)*z" by simp
+ also have "... = z+z" by (simp add: left_distrib)
+ finally show ?thesis .
+qed
+
+lemma nat_mult_2_right: "z * 2 = (z+z::nat)"
+by (subst mult_commute, rule nat_mult_2)
+
+text{*Case analysis on @{term "n<2"}*}
+lemma less_2_cases: "(n::nat) < 2 ==> n = 0 | n = Suc 0"
+by arith
+
+lemma div2_Suc_Suc [simp]: "Suc(Suc m) div 2 = Suc (m div 2)"
+by arith
+
+lemma add_self_div_2 [simp]: "(m + m) div 2 = (m::nat)"
+by (simp add: nat_mult_2 [symmetric])
+
+lemma mod2_Suc_Suc [simp]: "Suc(Suc(m)) mod 2 = m mod 2"
+apply (subgoal_tac "m mod 2 < 2")
+apply (erule less_2_cases [THEN disjE])
+apply (simp_all (no_asm_simp) add: Let_def mod_Suc nat_1)
+done
+
+lemma mod2_gr_0 [simp]: "!!m::nat. (0 < m mod 2) = (m mod 2 = 1)"
+apply (subgoal_tac "m mod 2 < 2")
+apply (force simp del: mod_less_divisor, simp)
+done
+
+subsubsection{*Removal of Small Numerals: 0, 1 and (in additive positions) 2*}
+
+lemma add_2_eq_Suc [simp]: "2 + n = Suc (Suc n)"
+by simp
+
+lemma add_2_eq_Suc' [simp]: "n + 2 = Suc (Suc n)"
+by simp
+
+text{*Can be used to eliminate long strings of Sucs, but not by default*}
+lemma Suc3_eq_add_3: "Suc (Suc (Suc n)) = 3 + n"
+by simp
+
+
+text{*These lemmas collapse some needless occurrences of Suc:
+ at least three Sucs, since two and fewer are rewritten back to Suc again!
+ We already have some rules to simplify operands smaller than 3.*}
+
+lemma div_Suc_eq_div_add3 [simp]: "m div (Suc (Suc (Suc n))) = m div (3+n)"
+by (simp add: Suc3_eq_add_3)
+
+lemma mod_Suc_eq_mod_add3 [simp]: "m mod (Suc (Suc (Suc n))) = m mod (3+n)"
+by (simp add: Suc3_eq_add_3)
+
+lemma Suc_div_eq_add3_div: "(Suc (Suc (Suc m))) div n = (3+m) div n"
+by (simp add: Suc3_eq_add_3)
+
+lemma Suc_mod_eq_add3_mod: "(Suc (Suc (Suc m))) mod n = (3+m) mod n"
+by (simp add: Suc3_eq_add_3)
+
+lemmas Suc_div_eq_add3_div_number_of =
+ Suc_div_eq_add3_div [of _ "number_of v", standard]
+declare Suc_div_eq_add3_div_number_of [simp]
+
+lemmas Suc_mod_eq_add3_mod_number_of =
+ Suc_mod_eq_add3_mod [of _ "number_of v", standard]
+declare Suc_mod_eq_add3_mod_number_of [simp]
+
+
+
+subsection{*Special Simplification for Constants*}
+
+text{*These belong here, late in the development of HOL, to prevent their
+interfering with proofs of abstract properties of instances of the function
+@{term number_of}*}
+
+text{*These distributive laws move literals inside sums and differences.*}
+lemmas left_distrib_number_of = left_distrib [of _ _ "number_of v", standard]
+declare left_distrib_number_of [simp]
+
+lemmas right_distrib_number_of = right_distrib [of "number_of v", standard]
+declare right_distrib_number_of [simp]
+
+
+lemmas left_diff_distrib_number_of =
+ left_diff_distrib [of _ _ "number_of v", standard]
+declare left_diff_distrib_number_of [simp]
+
+lemmas right_diff_distrib_number_of =
+ right_diff_distrib [of "number_of v", standard]
+declare right_diff_distrib_number_of [simp]
+
+
+text{*These are actually for fields, like real: but where else to put them?*}
+lemmas zero_less_divide_iff_number_of =
+ zero_less_divide_iff [of "number_of w", standard]
+declare zero_less_divide_iff_number_of [simp]
+
+lemmas divide_less_0_iff_number_of =
+ divide_less_0_iff [of "number_of w", standard]
+declare divide_less_0_iff_number_of [simp]
+
+lemmas zero_le_divide_iff_number_of =
+ zero_le_divide_iff [of "number_of w", standard]
+declare zero_le_divide_iff_number_of [simp]
+
+lemmas divide_le_0_iff_number_of =
+ divide_le_0_iff [of "number_of w", standard]
+declare divide_le_0_iff_number_of [simp]
+
+
+(****
+IF times_divide_eq_right and times_divide_eq_left are removed as simprules,
+then these special-case declarations may be useful.
+
+text{*These simprules move numerals into numerators and denominators.*}
+lemma times_recip_eq_right [simp]: "a * (1/c) = a / (c::'a::field)"
+by (simp add: times_divide_eq)
+
+lemma times_recip_eq_left [simp]: "(1/c) * a = a / (c::'a::field)"
+by (simp add: times_divide_eq)
+
+lemmas times_divide_eq_right_number_of =
+ times_divide_eq_right [of "number_of w", standard]
+declare times_divide_eq_right_number_of [simp]
+
+lemmas times_divide_eq_right_number_of =
+ times_divide_eq_right [of _ _ "number_of w", standard]
+declare times_divide_eq_right_number_of [simp]
+
+lemmas times_divide_eq_left_number_of =
+ times_divide_eq_left [of _ "number_of w", standard]
+declare times_divide_eq_left_number_of [simp]
+
+lemmas times_divide_eq_left_number_of =
+ times_divide_eq_left [of _ _ "number_of w", standard]
+declare times_divide_eq_left_number_of [simp]
+
+****)
+
+text {*Replaces @{text "inverse #nn"} by @{text "1/#nn"}. It looks
+ strange, but then other simprocs simplify the quotient.*}
+
+lemmas inverse_eq_divide_number_of =
+ inverse_eq_divide [of "number_of w", standard]
+declare inverse_eq_divide_number_of [simp]
+
+
+subsubsection{*These laws simplify inequalities, moving unary minus from a term
+into the literal.*}
+lemmas less_minus_iff_number_of =
+ less_minus_iff [of "number_of v", standard]
+declare less_minus_iff_number_of [simp]
+
+lemmas le_minus_iff_number_of =
+ le_minus_iff [of "number_of v", standard]
+declare le_minus_iff_number_of [simp]
+
+lemmas equation_minus_iff_number_of =
+ equation_minus_iff [of "number_of v", standard]
+declare equation_minus_iff_number_of [simp]
+
+
+lemmas minus_less_iff_number_of =
+ minus_less_iff [of _ "number_of v", standard]
+declare minus_less_iff_number_of [simp]
+
+lemmas minus_le_iff_number_of =
+ minus_le_iff [of _ "number_of v", standard]
+declare minus_le_iff_number_of [simp]
+
+lemmas minus_equation_iff_number_of =
+ minus_equation_iff [of _ "number_of v", standard]
+declare minus_equation_iff_number_of [simp]
+
+
+subsubsection{*To Simplify Inequalities Where One Side is the Constant 1*}
+
+lemma less_minus_iff_1 [simp]:
+ fixes b::"'b::{ordered_idom,number_ring}"
+ shows "(1 < - b) = (b < -1)"
+by auto
+
+lemma le_minus_iff_1 [simp]:
+ fixes b::"'b::{ordered_idom,number_ring}"
+ shows "(1 \<le> - b) = (b \<le> -1)"
+by auto
+
+lemma equation_minus_iff_1 [simp]:
+ fixes b::"'b::number_ring"
+ shows "(1 = - b) = (b = -1)"
+by (subst equation_minus_iff, auto)
+
+lemma minus_less_iff_1 [simp]:
+ fixes a::"'b::{ordered_idom,number_ring}"
+ shows "(- a < 1) = (-1 < a)"
+by auto
+
+lemma minus_le_iff_1 [simp]:
+ fixes a::"'b::{ordered_idom,number_ring}"
+ shows "(- a \<le> 1) = (-1 \<le> a)"
+by auto
+
+lemma minus_equation_iff_1 [simp]:
+ fixes a::"'b::number_ring"
+ shows "(- a = 1) = (a = -1)"
+by (subst minus_equation_iff, auto)
+
+
+subsubsection {*Cancellation of constant factors in comparisons (@{text "<"} and @{text "\<le>"}) *}
+
+lemmas mult_less_cancel_left_number_of =
+ mult_less_cancel_left [of "number_of v", standard]
+declare mult_less_cancel_left_number_of [simp]
+
+lemmas mult_less_cancel_right_number_of =
+ mult_less_cancel_right [of _ "number_of v", standard]
+declare mult_less_cancel_right_number_of [simp]
+
+lemmas mult_le_cancel_left_number_of =
+ mult_le_cancel_left [of "number_of v", standard]
+declare mult_le_cancel_left_number_of [simp]
+
+lemmas mult_le_cancel_right_number_of =
+ mult_le_cancel_right [of _ "number_of v", standard]
+declare mult_le_cancel_right_number_of [simp]
+
+
+subsubsection {*Multiplying out constant divisors in comparisons (@{text "<"}, @{text "\<le>"} and @{text "="}) *}
+
+lemmas le_divide_eq_number_of = le_divide_eq [of _ _ "number_of w", standard]
+declare le_divide_eq_number_of [simp]
+
+lemmas divide_le_eq_number_of = divide_le_eq [of _ "number_of w", standard]
+declare divide_le_eq_number_of [simp]
+
+lemmas less_divide_eq_number_of = less_divide_eq [of _ _ "number_of w", standard]
+declare less_divide_eq_number_of [simp]
+
+lemmas divide_less_eq_number_of = divide_less_eq [of _ "number_of w", standard]
+declare divide_less_eq_number_of [simp]
+
+lemmas eq_divide_eq_number_of = eq_divide_eq [of _ _ "number_of w", standard]
+declare eq_divide_eq_number_of [simp]
+
+lemmas divide_eq_eq_number_of = divide_eq_eq [of _ "number_of w", standard]
+declare divide_eq_eq_number_of [simp]
+
+
+
+subsection{*Optional Simplification Rules Involving Constants*}
+
+text{*Simplify quotients that are compared with a literal constant.*}
+
+lemmas le_divide_eq_number_of = le_divide_eq [of "number_of w", standard]
+lemmas divide_le_eq_number_of = divide_le_eq [of _ _ "number_of w", standard]
+lemmas less_divide_eq_number_of = less_divide_eq [of "number_of w", standard]
+lemmas divide_less_eq_number_of = divide_less_eq [of _ _ "number_of w", standard]
+lemmas eq_divide_eq_number_of = eq_divide_eq [of "number_of w", standard]
+lemmas divide_eq_eq_number_of = divide_eq_eq [of _ _ "number_of w", standard]
+
+
+text{*Not good as automatic simprules because they cause case splits.*}
+lemmas divide_const_simps =
+ le_divide_eq_number_of divide_le_eq_number_of less_divide_eq_number_of
+ divide_less_eq_number_of eq_divide_eq_number_of divide_eq_eq_number_of
+ le_divide_eq_1 divide_le_eq_1 less_divide_eq_1 divide_less_eq_1
+
+subsubsection{*Division By @{text "-1"}*}
+
+lemma divide_minus1 [simp]:
+ "x/-1 = -(x::'a::{field,division_by_zero,number_ring})"
+by simp
+
+lemma minus1_divide [simp]:
+ "-1 / (x::'a::{field,division_by_zero,number_ring}) = - (1/x)"
+by (simp add: divide_inverse inverse_minus_eq)
+
+lemma half_gt_zero_iff:
+ "(0 < r/2) = (0 < (r::'a::{ordered_field,division_by_zero,number_ring}))"
+by auto
+
+lemmas half_gt_zero = half_gt_zero_iff [THEN iffD2, standard]
+declare half_gt_zero [simp]
+
+(* The following lemma should appear in Divides.thy, but there the proof
+ doesn't work. *)
+
+lemma nat_dvd_not_less:
+ "[| 0 < m; m < n |] ==> \<not> n dvd (m::nat)"
+ by (unfold dvd_def) auto
+
+ML {*
+val divide_minus1 = @{thm divide_minus1};
+val minus1_divide = @{thm minus1_divide};
+*}
+
+end