src/HOL/Divides.thy
author haftmann
Thu May 17 19:49:16 2007 +0200 (2007-05-17)
changeset 22993 838c66e760b5
parent 22916 8caf6da610e2
child 23017 00c0e4c42396
permissions -rw-r--r--
tuned
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(*  Title:      HOL/Divides.thy
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    ID:         $Id$
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    Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
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    Copyright   1999  University of Cambridge
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*)
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header {* The division operators div, mod and the divides relation "dvd" *}
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theory Divides
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imports Datatype Power
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uses "~~/src/Provers/Arith/cancel_div_mod.ML"
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begin
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(*We use the same class for div and mod;
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  moreover, dvd is defined whenever multiplication is*)
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class div = type +
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  fixes div :: "'a \<Rightarrow> 'a \<Rightarrow> 'a"
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  fixes mod :: "'a \<Rightarrow> 'a \<Rightarrow> 'a"
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begin
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notation
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  div (infixl "\<^loc>div" 70)
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notation
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  mod (infixl "\<^loc>mod" 70)
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end
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notation
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  div (infixl "div" 70)
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notation
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  mod (infixl "mod" 70)
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instance nat :: Divides.div
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  div_def: "m div n == wfrec (pred_nat^+)
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                          (%f j. if j<n | n=0 then 0 else Suc (f (j-n))) m"
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  mod_def: "m mod n == wfrec (pred_nat^+)
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                          (%f j. if j<n | n=0 then j else f (j-n)) m" ..
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definition
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  (*The definition of dvd is polymorphic!*)
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  dvd  :: "'a::times \<Rightarrow> 'a \<Rightarrow> bool" (infixl "dvd" 50) where
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  dvd_def: "m dvd n \<longleftrightarrow> (\<exists>k. n = m*k)"
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definition
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  quorem :: "(nat*nat) * (nat*nat) => bool" where
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  (*This definition helps prove the harder properties of div and mod.
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    It is copied from IntDiv.thy; should it be overloaded?*)
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  "quorem = (%((a,b), (q,r)).
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                    a = b*q + r &
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                    (if 0<b then 0\<le>r & r<b else b<r & r \<le>0))"
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subsection{*Initial Lemmas*}
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lemmas wf_less_trans =
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       def_wfrec [THEN trans, OF eq_reflection wf_pred_nat [THEN wf_trancl],
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                  standard]
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lemma mod_eq: "(%m. m mod n) =
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              wfrec (pred_nat^+) (%f j. if j<n | n=0 then j else f (j-n))"
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by (simp add: mod_def)
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lemma div_eq: "(%m. m div n) = wfrec (pred_nat^+)
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               (%f j. if j<n | n=0 then 0 else Suc (f (j-n)))"
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by (simp add: div_def)
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(** Aribtrary definitions for division by zero.  Useful to simplify
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    certain equations **)
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lemma DIVISION_BY_ZERO_DIV [simp]: "a div 0 = (0::nat)"
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  by (rule div_eq [THEN wf_less_trans], simp)
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lemma DIVISION_BY_ZERO_MOD [simp]: "a mod 0 = (a::nat)"
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  by (rule mod_eq [THEN wf_less_trans], simp)
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subsection{*Remainder*}
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lemma mod_less [simp]: "m<n ==> m mod n = (m::nat)"
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  by (rule mod_eq [THEN wf_less_trans]) simp
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lemma mod_geq: "~ m < (n::nat) ==> m mod n = (m-n) mod n"
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  apply (cases "n=0")
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   apply simp
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  apply (rule mod_eq [THEN wf_less_trans])
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  apply (simp add: cut_apply less_eq)
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  done
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(*Avoids the ugly ~m<n above*)
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lemma le_mod_geq: "(n::nat) \<le> m ==> m mod n = (m-n) mod n"
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  by (simp add: mod_geq linorder_not_less)
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lemma mod_if: "m mod (n::nat) = (if m<n then m else (m-n) mod n)"
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  by (simp add: mod_geq)
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lemma mod_1 [simp]: "m mod Suc 0 = 0"
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  by (induct m) (simp_all add: mod_geq)
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lemma mod_self [simp]: "n mod n = (0::nat)"
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  by (cases "n = 0") (simp_all add: mod_geq)
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lemma mod_add_self2 [simp]: "(m+n) mod n = m mod (n::nat)"
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  apply (subgoal_tac "(n + m) mod n = (n+m-n) mod n")
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   apply (simp add: add_commute)
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  apply (subst mod_geq [symmetric], simp_all)
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  done
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lemma mod_add_self1 [simp]: "(n+m) mod n = m mod (n::nat)"
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  by (simp add: add_commute mod_add_self2)
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lemma mod_mult_self1 [simp]: "(m + k*n) mod n = m mod (n::nat)"
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  by (induct k) (simp_all add: add_left_commute [of _ n])
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lemma mod_mult_self2 [simp]: "(m + n*k) mod n = m mod (n::nat)"
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  by (simp add: mult_commute mod_mult_self1)
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lemma mod_mult_distrib: "(m mod n) * (k::nat) = (m*k) mod (n*k)"
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  apply (cases "n = 0", simp)
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  apply (cases "k = 0", simp)
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  apply (induct m rule: nat_less_induct)
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  apply (subst mod_if, simp)
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  apply (simp add: mod_geq diff_mult_distrib)
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  done
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lemma mod_mult_distrib2: "(k::nat) * (m mod n) = (k*m) mod (k*n)"
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  by (simp add: mult_commute [of k] mod_mult_distrib)
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lemma mod_mult_self_is_0 [simp]: "(m*n) mod n = (0::nat)"
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  apply (cases "n = 0", simp)
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  apply (induct m, simp)
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  apply (rename_tac k)
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  apply (cut_tac m = "k * n" and n = n in mod_add_self2)
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  apply (simp add: add_commute)
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  done
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lemma mod_mult_self1_is_0 [simp]: "(n*m) mod n = (0::nat)"
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  by (simp add: mult_commute mod_mult_self_is_0)
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subsection{*Quotient*}
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lemma div_less [simp]: "m<n ==> m div n = (0::nat)"
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  by (rule div_eq [THEN wf_less_trans], simp)
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lemma div_geq: "[| 0<n;  ~m<n |] ==> m div n = Suc((m-n) div n)"
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  apply (rule div_eq [THEN wf_less_trans])
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  apply (simp add: cut_apply less_eq)
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  done
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(*Avoids the ugly ~m<n above*)
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lemma le_div_geq: "[| 0<n;  n\<le>m |] ==> m div n = Suc((m-n) div n)"
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  by (simp add: div_geq linorder_not_less)
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lemma div_if: "0<n ==> m div n = (if m<n then 0 else Suc((m-n) div n))"
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  by (simp add: div_geq)
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(*Main Result about quotient and remainder.*)
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lemma mod_div_equality: "(m div n)*n + m mod n = (m::nat)"
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  apply (cases "n = 0", simp)
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  apply (induct m rule: nat_less_induct)
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  apply (subst mod_if)
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  apply (simp_all add: add_assoc div_geq add_diff_inverse)
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  done
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lemma mod_div_equality2: "n * (m div n) + m mod n = (m::nat)"
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  apply (cut_tac m = m and n = n in mod_div_equality)
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  apply (simp add: mult_commute)
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  done
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subsection{*Simproc for Cancelling Div and Mod*}
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lemma div_mod_equality: "((m div n)*n + m mod n) + k = (m::nat) + k"
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  by (simp add: mod_div_equality)
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lemma div_mod_equality2: "(n*(m div n) + m mod n) + k = (m::nat) + k"
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  by (simp add: mod_div_equality2)
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ML
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{*
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structure CancelDivModData =
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struct
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val div_name = @{const_name Divides.div};
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val mod_name = @{const_name Divides.mod};
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val mk_binop = HOLogic.mk_binop;
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val mk_sum = NatArithUtils.mk_sum;
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val dest_sum = NatArithUtils.dest_sum;
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(*logic*)
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val div_mod_eqs = map mk_meta_eq [@{thm div_mod_equality}, @{thm div_mod_equality2}]
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val trans = trans
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val prove_eq_sums =
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  let val simps = @{thm add_0} :: @{thm add_0_right} :: @{thms add_ac}
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  in NatArithUtils.prove_conv all_tac (NatArithUtils.simp_all_tac simps) end;
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end;
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structure CancelDivMod = CancelDivModFun(CancelDivModData);
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val cancel_div_mod_proc = NatArithUtils.prep_simproc
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      ("cancel_div_mod", ["(m::nat) + n"], K CancelDivMod.proc);
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Addsimprocs[cancel_div_mod_proc];
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*}
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(* a simple rearrangement of mod_div_equality: *)
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lemma mult_div_cancel: "(n::nat) * (m div n) = m - (m mod n)"
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  by (cut_tac m = m and n = n in mod_div_equality2, arith)
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lemma mod_less_divisor [simp]: "0<n ==> m mod n < (n::nat)"
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  apply (induct m rule: nat_less_induct)
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  apply (rename_tac m)
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  apply (case_tac "m<n", simp)
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  txt{*case @{term "n \<le> m"}*}
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  apply (simp add: mod_geq)
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  done
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lemma mod_le_divisor[simp]: "0 < n \<Longrightarrow> m mod n \<le> (n::nat)"
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  apply (drule mod_less_divisor [where m = m])
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  apply simp
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  done
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lemma div_mult_self_is_m [simp]: "0<n ==> (m*n) div n = (m::nat)"
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  by (cut_tac m = "m*n" and n = n in mod_div_equality, auto)
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lemma div_mult_self1_is_m [simp]: "0<n ==> (n*m) div n = (m::nat)"
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  by (simp add: mult_commute div_mult_self_is_m)
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(*mod_mult_distrib2 above is the counterpart for remainder*)
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subsection{*Proving facts about Quotient and Remainder*}
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lemma unique_quotient_lemma:
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     "[| b*q' + r'  \<le> b*q + r;  x < b;  r < b |]
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      ==> q' \<le> (q::nat)"
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  apply (rule leI)
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  apply (subst less_iff_Suc_add)
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  apply (auto simp add: add_mult_distrib2)
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  done
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lemma unique_quotient:
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     "[| quorem ((a,b), (q,r));  quorem ((a,b), (q',r'));  0 < b |]
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      ==> q = q'"
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  apply (simp add: split_ifs quorem_def)
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  apply (blast intro: order_antisym
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    dest: order_eq_refl [THEN unique_quotient_lemma] sym)
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  done
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lemma unique_remainder:
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     "[| quorem ((a,b), (q,r));  quorem ((a,b), (q',r'));  0 < b |]
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      ==> r = r'"
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  apply (subgoal_tac "q = q'")
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   prefer 2 apply (blast intro: unique_quotient)
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  apply (simp add: quorem_def)
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  done
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lemma quorem_div_mod: "0 < b ==> quorem ((a, b), (a div b, a mod b))"
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  unfolding quorem_def by simp
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lemma quorem_div: "[| quorem((a,b),(q,r));  0 < b |] ==> a div b = q"
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  by (simp add: quorem_div_mod [THEN unique_quotient])
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lemma quorem_mod: "[| quorem((a,b),(q,r));  0 < b |] ==> a mod b = r"
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  by (simp add: quorem_div_mod [THEN unique_remainder])
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(** A dividend of zero **)
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lemma div_0 [simp]: "0 div m = (0::nat)"
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  by (cases "m = 0") simp_all
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lemma mod_0 [simp]: "0 mod m = (0::nat)"
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  by (cases "m = 0") simp_all
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(** proving (a*b) div c = a * (b div c) + a * (b mod c) **)
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lemma quorem_mult1_eq:
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     "[| quorem((b,c),(q,r));  0 < c |]
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      ==> quorem ((a*b, c), (a*q + a*r div c, a*r mod c))"
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  by (auto simp add: split_ifs mult_ac quorem_def add_mult_distrib2)
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lemma div_mult1_eq: "(a*b) div c = a*(b div c) + a*(b mod c) div (c::nat)"
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  apply (cases "c = 0", simp)
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  apply (blast intro: quorem_div_mod [THEN quorem_mult1_eq, THEN quorem_div])
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  done
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lemma mod_mult1_eq: "(a*b) mod c = a*(b mod c) mod (c::nat)"
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  apply (cases "c = 0", simp)
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  apply (blast intro: quorem_div_mod [THEN quorem_mult1_eq, THEN quorem_mod])
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  done
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lemma mod_mult1_eq': "(a*b) mod (c::nat) = ((a mod c) * b) mod c"
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  apply (rule trans)
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   apply (rule_tac s = "b*a mod c" in trans)
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    apply (rule_tac [2] mod_mult1_eq)
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   apply (simp_all add: mult_commute)
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  done
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lemma mod_mult_distrib_mod: "(a*b) mod (c::nat) = ((a mod c) * (b mod c)) mod c"
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  apply (rule mod_mult1_eq' [THEN trans])
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  apply (rule mod_mult1_eq)
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  done
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(** proving (a+b) div c = a div c + b div c + ((a mod c + b mod c) div c) **)
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lemma quorem_add1_eq:
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     "[| quorem((a,c),(aq,ar));  quorem((b,c),(bq,br));  0 < c |]
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      ==> quorem ((a+b, c), (aq + bq + (ar+br) div c, (ar+br) mod c))"
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  by (auto simp add: split_ifs mult_ac quorem_def add_mult_distrib2)
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(*NOT suitable for rewriting: the RHS has an instance of the LHS*)
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lemma div_add1_eq:
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   322
     "(a+b) div (c::nat) = a div c + b div c + ((a mod c + b mod c) div c)"
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   323
  apply (cases "c = 0", simp)
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   324
  apply (blast intro: quorem_add1_eq [THEN quorem_div] quorem_div_mod quorem_div_mod)
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   325
  done
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   326
paulson@14267
   327
lemma mod_add1_eq: "(a+b) mod (c::nat) = (a mod c + b mod c) mod c"
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   328
  apply (cases "c = 0", simp)
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   329
  apply (blast intro: quorem_div_mod quorem_div_mod quorem_add1_eq [THEN quorem_mod])
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   330
  done
paulson@14267
   331
paulson@14267
   332
paulson@14267
   333
subsection{*Proving @{term "a div (b*c) = (a div b) div c"}*}
paulson@14267
   334
paulson@14267
   335
(** first, a lemma to bound the remainder **)
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   336
paulson@14267
   337
lemma mod_lemma: "[| (0::nat) < c; r < b |] ==> b * (q mod c) + r < b * c"
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   338
  apply (cut_tac m = q and n = c in mod_less_divisor)
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   339
  apply (drule_tac [2] m = "q mod c" in less_imp_Suc_add, auto)
wenzelm@22718
   340
  apply (erule_tac P = "%x. ?lhs < ?rhs x" in ssubst)
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   341
  apply (simp add: add_mult_distrib2)
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   342
  done
paulson@10559
   343
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   344
lemma quorem_mult2_eq: "[| quorem ((a,b), (q,r));  0 < b;  0 < c |]
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   345
      ==> quorem ((a, b*c), (q div c, b*(q mod c) + r))"
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   346
  by (auto simp add: mult_ac quorem_def add_mult_distrib2 [symmetric] mod_lemma)
paulson@14267
   347
paulson@14267
   348
lemma div_mult2_eq: "a div (b*c) = (a div b) div (c::nat)"
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   349
  apply (cases "b = 0", simp)
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   350
  apply (cases "c = 0", simp)
wenzelm@22718
   351
  apply (force simp add: quorem_div_mod [THEN quorem_mult2_eq, THEN quorem_div])
wenzelm@22718
   352
  done
paulson@14267
   353
paulson@14267
   354
lemma mod_mult2_eq: "a mod (b*c) = b*(a div b mod c) + a mod (b::nat)"
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   355
  apply (cases "b = 0", simp)
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   356
  apply (cases "c = 0", simp)
wenzelm@22718
   357
  apply (auto simp add: mult_commute quorem_div_mod [THEN quorem_mult2_eq, THEN quorem_mod])
wenzelm@22718
   358
  done
paulson@14267
   359
paulson@14267
   360
paulson@14267
   361
subsection{*Cancellation of Common Factors in Division*}
paulson@14267
   362
paulson@14267
   363
lemma div_mult_mult_lemma:
wenzelm@22718
   364
    "[| (0::nat) < b;  0 < c |] ==> (c*a) div (c*b) = a div b"
wenzelm@22718
   365
  by (auto simp add: div_mult2_eq)
paulson@14267
   366
paulson@14267
   367
lemma div_mult_mult1 [simp]: "(0::nat) < c ==> (c*a) div (c*b) = a div b"
wenzelm@22718
   368
  apply (cases "b = 0")
wenzelm@22718
   369
  apply (auto simp add: linorder_neq_iff [of b] div_mult_mult_lemma)
wenzelm@22718
   370
  done
paulson@14267
   371
paulson@14267
   372
lemma div_mult_mult2 [simp]: "(0::nat) < c ==> (a*c) div (b*c) = a div b"
wenzelm@22718
   373
  apply (drule div_mult_mult1)
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   374
  apply (auto simp add: mult_commute)
wenzelm@22718
   375
  done
paulson@14267
   376
paulson@14267
   377
paulson@14267
   378
(*Distribution of Factors over Remainders:
paulson@14267
   379
paulson@14267
   380
Could prove these as in Integ/IntDiv.ML, but we already have
paulson@14267
   381
mod_mult_distrib and mod_mult_distrib2 above!
paulson@14267
   382
paulson@14267
   383
Goal "(c*a) mod (c*b) = (c::nat) * (a mod b)"
paulson@14267
   384
qed "mod_mult_mult1";
paulson@14267
   385
paulson@14267
   386
Goal "(a*c) mod (b*c) = (a mod b) * (c::nat)";
paulson@14267
   387
qed "mod_mult_mult2";
paulson@14267
   388
 ***)
paulson@14267
   389
paulson@14267
   390
subsection{*Further Facts about Quotient and Remainder*}
paulson@14267
   391
paulson@14267
   392
lemma div_1 [simp]: "m div Suc 0 = m"
wenzelm@22718
   393
  by (induct m) (simp_all add: div_geq)
paulson@14267
   394
paulson@14267
   395
lemma div_self [simp]: "0<n ==> n div n = (1::nat)"
wenzelm@22718
   396
  by (simp add: div_geq)
paulson@14267
   397
paulson@14267
   398
lemma div_add_self2: "0<n ==> (m+n) div n = Suc (m div n)"
wenzelm@22718
   399
  apply (subgoal_tac "(n + m) div n = Suc ((n+m-n) div n) ")
wenzelm@22718
   400
   apply (simp add: add_commute)
wenzelm@22718
   401
  apply (subst div_geq [symmetric], simp_all)
wenzelm@22718
   402
  done
paulson@14267
   403
paulson@14267
   404
lemma div_add_self1: "0<n ==> (n+m) div n = Suc (m div n)"
wenzelm@22718
   405
  by (simp add: add_commute div_add_self2)
paulson@14267
   406
paulson@14267
   407
lemma div_mult_self1 [simp]: "!!n::nat. 0<n ==> (m + k*n) div n = k + m div n"
wenzelm@22718
   408
  apply (subst div_add1_eq)
wenzelm@22718
   409
  apply (subst div_mult1_eq, simp)
wenzelm@22718
   410
  done
paulson@14267
   411
paulson@14267
   412
lemma div_mult_self2 [simp]: "0<n ==> (m + n*k) div n = k + m div (n::nat)"
wenzelm@22718
   413
  by (simp add: mult_commute div_mult_self1)
paulson@14267
   414
paulson@14267
   415
paulson@14267
   416
(* Monotonicity of div in first argument *)
paulson@14267
   417
lemma div_le_mono [rule_format (no_asm)]:
wenzelm@22718
   418
    "\<forall>m::nat. m \<le> n --> (m div k) \<le> (n div k)"
paulson@14267
   419
apply (case_tac "k=0", simp)
paulson@15251
   420
apply (induct "n" rule: nat_less_induct, clarify)
paulson@14267
   421
apply (case_tac "n<k")
paulson@14267
   422
(* 1  case n<k *)
paulson@14267
   423
apply simp
paulson@14267
   424
(* 2  case n >= k *)
paulson@14267
   425
apply (case_tac "m<k")
paulson@14267
   426
(* 2.1  case m<k *)
paulson@14267
   427
apply simp
paulson@14267
   428
(* 2.2  case m>=k *)
nipkow@15439
   429
apply (simp add: div_geq diff_le_mono)
paulson@14267
   430
done
paulson@14267
   431
paulson@14267
   432
(* Antimonotonicity of div in second argument *)
paulson@14267
   433
lemma div_le_mono2: "!!m::nat. [| 0<m; m\<le>n |] ==> (k div n) \<le> (k div m)"
paulson@14267
   434
apply (subgoal_tac "0<n")
wenzelm@22718
   435
 prefer 2 apply simp
paulson@15251
   436
apply (induct_tac k rule: nat_less_induct)
paulson@14267
   437
apply (rename_tac "k")
paulson@14267
   438
apply (case_tac "k<n", simp)
paulson@14267
   439
apply (subgoal_tac "~ (k<m) ")
wenzelm@22718
   440
 prefer 2 apply simp
paulson@14267
   441
apply (simp add: div_geq)
paulson@15251
   442
apply (subgoal_tac "(k-n) div n \<le> (k-m) div n")
paulson@14267
   443
 prefer 2
paulson@14267
   444
 apply (blast intro: div_le_mono diff_le_mono2)
paulson@14267
   445
apply (rule le_trans, simp)
nipkow@15439
   446
apply (simp)
paulson@14267
   447
done
paulson@14267
   448
paulson@14267
   449
lemma div_le_dividend [simp]: "m div n \<le> (m::nat)"
paulson@14267
   450
apply (case_tac "n=0", simp)
paulson@14267
   451
apply (subgoal_tac "m div n \<le> m div 1", simp)
paulson@14267
   452
apply (rule div_le_mono2)
paulson@14267
   453
apply (simp_all (no_asm_simp))
paulson@14267
   454
done
paulson@14267
   455
wenzelm@22718
   456
(* Similar for "less than" *)
paulson@17085
   457
lemma div_less_dividend [rule_format]:
paulson@14267
   458
     "!!n::nat. 1<n ==> 0 < m --> m div n < m"
paulson@15251
   459
apply (induct_tac m rule: nat_less_induct)
paulson@14267
   460
apply (rename_tac "m")
paulson@14267
   461
apply (case_tac "m<n", simp)
paulson@14267
   462
apply (subgoal_tac "0<n")
wenzelm@22718
   463
 prefer 2 apply simp
paulson@14267
   464
apply (simp add: div_geq)
paulson@14267
   465
apply (case_tac "n<m")
paulson@15251
   466
 apply (subgoal_tac "(m-n) div n < (m-n) ")
paulson@14267
   467
  apply (rule impI less_trans_Suc)+
paulson@14267
   468
apply assumption
nipkow@15439
   469
  apply (simp_all)
paulson@14267
   470
done
paulson@14267
   471
paulson@17085
   472
declare div_less_dividend [simp]
paulson@17085
   473
paulson@14267
   474
text{*A fact for the mutilated chess board*}
paulson@14267
   475
lemma mod_Suc: "Suc(m) mod n = (if Suc(m mod n) = n then 0 else Suc(m mod n))"
paulson@14267
   476
apply (case_tac "n=0", simp)
paulson@15251
   477
apply (induct "m" rule: nat_less_induct)
paulson@14267
   478
apply (case_tac "Suc (na) <n")
paulson@14267
   479
(* case Suc(na) < n *)
paulson@14267
   480
apply (frule lessI [THEN less_trans], simp add: less_not_refl3)
paulson@14267
   481
(* case n \<le> Suc(na) *)
paulson@16796
   482
apply (simp add: linorder_not_less le_Suc_eq mod_geq)
nipkow@15439
   483
apply (auto simp add: Suc_diff_le le_mod_geq)
paulson@14267
   484
done
paulson@14267
   485
paulson@14437
   486
lemma nat_mod_div_trivial [simp]: "m mod n div n = (0 :: nat)"
wenzelm@22718
   487
  by (cases "n = 0") auto
paulson@14437
   488
paulson@14437
   489
lemma nat_mod_mod_trivial [simp]: "m mod n mod n = (m mod n :: nat)"
wenzelm@22718
   490
  by (cases "n = 0") auto
paulson@14437
   491
paulson@14267
   492
paulson@14267
   493
subsection{*The Divides Relation*}
paulson@14267
   494
paulson@14267
   495
lemma dvdI [intro?]: "n = m * k ==> m dvd n"
wenzelm@22718
   496
  unfolding dvd_def by blast
paulson@14267
   497
paulson@14267
   498
lemma dvdE [elim?]: "!!P. [|m dvd n;  !!k. n = m*k ==> P|] ==> P"
wenzelm@22718
   499
  unfolding dvd_def by blast
nipkow@13152
   500
paulson@14267
   501
lemma dvd_0_right [iff]: "m dvd (0::nat)"
wenzelm@22718
   502
  unfolding dvd_def by (blast intro: mult_0_right [symmetric])
paulson@14267
   503
paulson@14267
   504
lemma dvd_0_left: "0 dvd m ==> m = (0::nat)"
wenzelm@22718
   505
  by (force simp add: dvd_def)
paulson@14267
   506
paulson@14267
   507
lemma dvd_0_left_iff [iff]: "(0 dvd (m::nat)) = (m = 0)"
wenzelm@22718
   508
  by (blast intro: dvd_0_left)
paulson@14267
   509
paulson@14267
   510
lemma dvd_1_left [iff]: "Suc 0 dvd k"
wenzelm@22718
   511
  unfolding dvd_def by simp
paulson@14267
   512
paulson@14267
   513
lemma dvd_1_iff_1 [simp]: "(m dvd Suc 0) = (m = Suc 0)"
wenzelm@22718
   514
  by (simp add: dvd_def)
paulson@14267
   515
paulson@14267
   516
lemma dvd_refl [simp]: "m dvd (m::nat)"
wenzelm@22718
   517
  unfolding dvd_def by (blast intro: mult_1_right [symmetric])
paulson@14267
   518
paulson@14267
   519
lemma dvd_trans [trans]: "[| m dvd n; n dvd p |] ==> m dvd (p::nat)"
wenzelm@22718
   520
  unfolding dvd_def by (blast intro: mult_assoc)
paulson@14267
   521
paulson@14267
   522
lemma dvd_anti_sym: "[| m dvd n; n dvd m |] ==> m = (n::nat)"
wenzelm@22718
   523
  unfolding dvd_def
wenzelm@22718
   524
  by (force dest: mult_eq_self_implies_10 simp add: mult_assoc mult_eq_1_iff)
paulson@14267
   525
paulson@14267
   526
lemma dvd_add: "[| k dvd m; k dvd n |] ==> k dvd (m+n :: nat)"
wenzelm@22718
   527
  unfolding dvd_def
wenzelm@22718
   528
  by (blast intro: add_mult_distrib2 [symmetric])
paulson@14267
   529
paulson@14267
   530
lemma dvd_diff: "[| k dvd m; k dvd n |] ==> k dvd (m-n :: nat)"
wenzelm@22718
   531
  unfolding dvd_def
wenzelm@22718
   532
  by (blast intro: diff_mult_distrib2 [symmetric])
paulson@14267
   533
paulson@14267
   534
lemma dvd_diffD: "[| k dvd m-n; k dvd n; n\<le>m |] ==> k dvd (m::nat)"
wenzelm@22718
   535
  apply (erule linorder_not_less [THEN iffD2, THEN add_diff_inverse, THEN subst])
wenzelm@22718
   536
  apply (blast intro: dvd_add)
wenzelm@22718
   537
  done
paulson@14267
   538
paulson@14267
   539
lemma dvd_diffD1: "[| k dvd m-n; k dvd m; n\<le>m |] ==> k dvd (n::nat)"
wenzelm@22718
   540
  by (drule_tac m = m in dvd_diff, auto)
paulson@14267
   541
paulson@14267
   542
lemma dvd_mult: "k dvd n ==> k dvd (m*n :: nat)"
wenzelm@22718
   543
  unfolding dvd_def by (blast intro: mult_left_commute)
paulson@14267
   544
paulson@14267
   545
lemma dvd_mult2: "k dvd m ==> k dvd (m*n :: nat)"
wenzelm@22718
   546
  apply (subst mult_commute)
wenzelm@22718
   547
  apply (erule dvd_mult)
wenzelm@22718
   548
  done
paulson@14267
   549
paulson@17084
   550
lemma dvd_triv_right [iff]: "k dvd (m*k :: nat)"
wenzelm@22718
   551
  by (rule dvd_refl [THEN dvd_mult])
paulson@17084
   552
paulson@17084
   553
lemma dvd_triv_left [iff]: "k dvd (k*m :: nat)"
wenzelm@22718
   554
  by (rule dvd_refl [THEN dvd_mult2])
paulson@14267
   555
paulson@14267
   556
lemma dvd_reduce: "(k dvd n + k) = (k dvd (n::nat))"
wenzelm@22718
   557
  apply (rule iffI)
wenzelm@22718
   558
   apply (erule_tac [2] dvd_add)
wenzelm@22718
   559
   apply (rule_tac [2] dvd_refl)
wenzelm@22718
   560
  apply (subgoal_tac "n = (n+k) -k")
wenzelm@22718
   561
   prefer 2 apply simp
wenzelm@22718
   562
  apply (erule ssubst)
wenzelm@22718
   563
  apply (erule dvd_diff)
wenzelm@22718
   564
  apply (rule dvd_refl)
wenzelm@22718
   565
  done
paulson@14267
   566
paulson@14267
   567
lemma dvd_mod: "!!n::nat. [| f dvd m; f dvd n |] ==> f dvd m mod n"
wenzelm@22718
   568
  unfolding dvd_def
wenzelm@22718
   569
  apply (case_tac "n = 0", auto)
wenzelm@22718
   570
  apply (blast intro: mod_mult_distrib2 [symmetric])
wenzelm@22718
   571
  done
paulson@14267
   572
paulson@14267
   573
lemma dvd_mod_imp_dvd: "[| (k::nat) dvd m mod n;  k dvd n |] ==> k dvd m"
wenzelm@22718
   574
  apply (subgoal_tac "k dvd (m div n) *n + m mod n")
wenzelm@22718
   575
   apply (simp add: mod_div_equality)
wenzelm@22718
   576
  apply (simp only: dvd_add dvd_mult)
wenzelm@22718
   577
  done
paulson@14267
   578
paulson@14267
   579
lemma dvd_mod_iff: "k dvd n ==> ((k::nat) dvd m mod n) = (k dvd m)"
wenzelm@22718
   580
  by (blast intro: dvd_mod_imp_dvd dvd_mod)
paulson@14267
   581
paulson@14267
   582
lemma dvd_mult_cancel: "!!k::nat. [| k*m dvd k*n; 0<k |] ==> m dvd n"
wenzelm@22718
   583
  unfolding dvd_def
wenzelm@22718
   584
  apply (erule exE)
wenzelm@22718
   585
  apply (simp add: mult_ac)
wenzelm@22718
   586
  done
paulson@14267
   587
paulson@14267
   588
lemma dvd_mult_cancel1: "0<m ==> (m*n dvd m) = (n = (1::nat))"
wenzelm@22718
   589
  apply auto
wenzelm@22718
   590
   apply (subgoal_tac "m*n dvd m*1")
wenzelm@22718
   591
   apply (drule dvd_mult_cancel, auto)
wenzelm@22718
   592
  done
paulson@14267
   593
paulson@14267
   594
lemma dvd_mult_cancel2: "0<m ==> (n*m dvd m) = (n = (1::nat))"
wenzelm@22718
   595
  apply (subst mult_commute)
wenzelm@22718
   596
  apply (erule dvd_mult_cancel1)
wenzelm@22718
   597
  done
paulson@14267
   598
paulson@14267
   599
lemma mult_dvd_mono: "[| i dvd m; j dvd n|] ==> i*j dvd (m*n :: nat)"
wenzelm@22718
   600
  apply (unfold dvd_def, clarify)
wenzelm@22718
   601
  apply (rule_tac x = "k*ka" in exI)
wenzelm@22718
   602
  apply (simp add: mult_ac)
wenzelm@22718
   603
  done
paulson@14267
   604
paulson@14267
   605
lemma dvd_mult_left: "(i*j :: nat) dvd k ==> i dvd k"
wenzelm@22718
   606
  by (simp add: dvd_def mult_assoc, blast)
paulson@14267
   607
paulson@14267
   608
lemma dvd_mult_right: "(i*j :: nat) dvd k ==> j dvd k"
wenzelm@22718
   609
  apply (unfold dvd_def, clarify)
wenzelm@22718
   610
  apply (rule_tac x = "i*k" in exI)
wenzelm@22718
   611
  apply (simp add: mult_ac)
wenzelm@22718
   612
  done
paulson@14267
   613
paulson@14267
   614
lemma dvd_imp_le: "[| k dvd n; 0 < n |] ==> k \<le> (n::nat)"
wenzelm@22718
   615
  apply (unfold dvd_def, clarify)
wenzelm@22718
   616
  apply (simp_all (no_asm_use) add: zero_less_mult_iff)
wenzelm@22718
   617
  apply (erule conjE)
wenzelm@22718
   618
  apply (rule le_trans)
wenzelm@22718
   619
   apply (rule_tac [2] le_refl [THEN mult_le_mono])
wenzelm@22718
   620
   apply (erule_tac [2] Suc_leI, simp)
wenzelm@22718
   621
  done
paulson@14267
   622
paulson@14267
   623
lemma dvd_eq_mod_eq_0: "!!k::nat. (k dvd n) = (n mod k = 0)"
wenzelm@22718
   624
  apply (unfold dvd_def)
wenzelm@22718
   625
  apply (case_tac "k=0", simp, safe)
wenzelm@22718
   626
   apply (simp add: mult_commute)
wenzelm@22718
   627
  apply (rule_tac t = n and n1 = k in mod_div_equality [THEN subst])
wenzelm@22718
   628
  apply (subst mult_commute, simp)
wenzelm@22718
   629
  done
paulson@14267
   630
paulson@14267
   631
lemma dvd_mult_div_cancel: "n dvd m ==> n * (m div n) = (m::nat)"
wenzelm@22718
   632
  apply (subgoal_tac "m mod n = 0")
wenzelm@22718
   633
   apply (simp add: mult_div_cancel)
wenzelm@22718
   634
  apply (simp only: dvd_eq_mod_eq_0)
wenzelm@22718
   635
  done
paulson@14267
   636
haftmann@21408
   637
lemma le_imp_power_dvd: "!!i::nat. m \<le> n ==> i^m dvd i^n"
wenzelm@22718
   638
  apply (unfold dvd_def)
wenzelm@22718
   639
  apply (erule linorder_not_less [THEN iffD2, THEN add_diff_inverse, THEN subst])
wenzelm@22718
   640
  apply (simp add: power_add)
wenzelm@22718
   641
  done
haftmann@21408
   642
haftmann@21408
   643
lemma nat_zero_less_power_iff [simp]: "(0 < x^n) = (x \<noteq> (0::nat) | n=0)"
wenzelm@22718
   644
  by (induct n) auto
haftmann@21408
   645
haftmann@21408
   646
lemma power_le_dvd [rule_format]: "k^j dvd n --> i\<le>j --> k^i dvd (n::nat)"
wenzelm@22718
   647
  apply (induct j)
wenzelm@22718
   648
   apply (simp_all add: le_Suc_eq)
wenzelm@22718
   649
  apply (blast dest!: dvd_mult_right)
wenzelm@22718
   650
  done
haftmann@21408
   651
haftmann@21408
   652
lemma power_dvd_imp_le: "[|i^m dvd i^n;  (1::nat) < i|] ==> m \<le> n"
wenzelm@22718
   653
  apply (rule power_le_imp_le_exp, assumption)
wenzelm@22718
   654
  apply (erule dvd_imp_le, simp)
wenzelm@22718
   655
  done
haftmann@21408
   656
paulson@14267
   657
lemma mod_eq_0_iff: "(m mod d = 0) = (\<exists>q::nat. m = d*q)"
wenzelm@22718
   658
  by (auto simp add: dvd_eq_mod_eq_0 [symmetric] dvd_def)
paulson@17084
   659
wenzelm@22718
   660
lemmas mod_eq_0D [dest!] = mod_eq_0_iff [THEN iffD1]
paulson@14267
   661
paulson@14267
   662
(*Loses information, namely we also have r<d provided d is nonzero*)
paulson@14267
   663
lemma mod_eqD: "(m mod d = r) ==> \<exists>q::nat. m = r + q*d"
wenzelm@22718
   664
  apply (cut_tac m = m in mod_div_equality)
wenzelm@22718
   665
  apply (simp only: add_ac)
wenzelm@22718
   666
  apply (blast intro: sym)
wenzelm@22718
   667
  done
paulson@14267
   668
paulson@14131
   669
nipkow@13152
   670
lemma split_div:
nipkow@13189
   671
 "P(n div k :: nat) =
nipkow@13189
   672
 ((k = 0 \<longrightarrow> P 0) \<and> (k \<noteq> 0 \<longrightarrow> (!i. !j<k. n = k*i + j \<longrightarrow> P i)))"
nipkow@13189
   673
 (is "?P = ?Q" is "_ = (_ \<and> (_ \<longrightarrow> ?R))")
nipkow@13189
   674
proof
nipkow@13189
   675
  assume P: ?P
nipkow@13189
   676
  show ?Q
nipkow@13189
   677
  proof (cases)
nipkow@13189
   678
    assume "k = 0"
nipkow@13189
   679
    with P show ?Q by(simp add:DIVISION_BY_ZERO_DIV)
nipkow@13189
   680
  next
nipkow@13189
   681
    assume not0: "k \<noteq> 0"
nipkow@13189
   682
    thus ?Q
nipkow@13189
   683
    proof (simp, intro allI impI)
nipkow@13189
   684
      fix i j
nipkow@13189
   685
      assume n: "n = k*i + j" and j: "j < k"
nipkow@13189
   686
      show "P i"
nipkow@13189
   687
      proof (cases)
wenzelm@22718
   688
        assume "i = 0"
wenzelm@22718
   689
        with n j P show "P i" by simp
nipkow@13189
   690
      next
wenzelm@22718
   691
        assume "i \<noteq> 0"
wenzelm@22718
   692
        with not0 n j P show "P i" by(simp add:add_ac)
nipkow@13189
   693
      qed
nipkow@13189
   694
    qed
nipkow@13189
   695
  qed
nipkow@13189
   696
next
nipkow@13189
   697
  assume Q: ?Q
nipkow@13189
   698
  show ?P
nipkow@13189
   699
  proof (cases)
nipkow@13189
   700
    assume "k = 0"
nipkow@13189
   701
    with Q show ?P by(simp add:DIVISION_BY_ZERO_DIV)
nipkow@13189
   702
  next
nipkow@13189
   703
    assume not0: "k \<noteq> 0"
nipkow@13189
   704
    with Q have R: ?R by simp
nipkow@13189
   705
    from not0 R[THEN spec,of "n div k",THEN spec, of "n mod k"]
nipkow@13517
   706
    show ?P by simp
nipkow@13189
   707
  qed
nipkow@13189
   708
qed
nipkow@13189
   709
berghofe@13882
   710
lemma split_div_lemma:
paulson@14267
   711
  "0 < n \<Longrightarrow> (n * q \<le> m \<and> m < n * (Suc q)) = (q = ((m::nat) div n))"
berghofe@13882
   712
  apply (rule iffI)
berghofe@13882
   713
  apply (rule_tac a=m and r = "m - n * q" and r' = "m mod n" in unique_quotient)
nipkow@16733
   714
prefer 3; apply assumption
webertj@20432
   715
  apply (simp_all add: quorem_def) apply arith
berghofe@13882
   716
  apply (rule conjI)
berghofe@13882
   717
  apply (rule_tac P="%x. n * (m div n) \<le> x" in
berghofe@13882
   718
    subst [OF mod_div_equality [of _ n]])
berghofe@13882
   719
  apply (simp only: add: mult_ac)
berghofe@13882
   720
  apply (rule_tac P="%x. x < n + n * (m div n)" in
berghofe@13882
   721
    subst [OF mod_div_equality [of _ n]])
berghofe@13882
   722
  apply (simp only: add: mult_ac add_ac)
paulson@14208
   723
  apply (rule add_less_mono1, simp)
berghofe@13882
   724
  done
berghofe@13882
   725
berghofe@13882
   726
theorem split_div':
berghofe@13882
   727
  "P ((m::nat) div n) = ((n = 0 \<and> P 0) \<or>
paulson@14267
   728
   (\<exists>q. (n * q \<le> m \<and> m < n * (Suc q)) \<and> P q))"
berghofe@13882
   729
  apply (case_tac "0 < n")
berghofe@13882
   730
  apply (simp only: add: split_div_lemma)
berghofe@13882
   731
  apply (simp_all add: DIVISION_BY_ZERO_DIV)
berghofe@13882
   732
  done
berghofe@13882
   733
nipkow@13189
   734
lemma split_mod:
nipkow@13189
   735
 "P(n mod k :: nat) =
nipkow@13189
   736
 ((k = 0 \<longrightarrow> P n) \<and> (k \<noteq> 0 \<longrightarrow> (!i. !j<k. n = k*i + j \<longrightarrow> P j)))"
nipkow@13189
   737
 (is "?P = ?Q" is "_ = (_ \<and> (_ \<longrightarrow> ?R))")
nipkow@13189
   738
proof
nipkow@13189
   739
  assume P: ?P
nipkow@13189
   740
  show ?Q
nipkow@13189
   741
  proof (cases)
nipkow@13189
   742
    assume "k = 0"
nipkow@13189
   743
    with P show ?Q by(simp add:DIVISION_BY_ZERO_MOD)
nipkow@13189
   744
  next
nipkow@13189
   745
    assume not0: "k \<noteq> 0"
nipkow@13189
   746
    thus ?Q
nipkow@13189
   747
    proof (simp, intro allI impI)
nipkow@13189
   748
      fix i j
nipkow@13189
   749
      assume "n = k*i + j" "j < k"
nipkow@13189
   750
      thus "P j" using not0 P by(simp add:add_ac mult_ac)
nipkow@13189
   751
    qed
nipkow@13189
   752
  qed
nipkow@13189
   753
next
nipkow@13189
   754
  assume Q: ?Q
nipkow@13189
   755
  show ?P
nipkow@13189
   756
  proof (cases)
nipkow@13189
   757
    assume "k = 0"
nipkow@13189
   758
    with Q show ?P by(simp add:DIVISION_BY_ZERO_MOD)
nipkow@13189
   759
  next
nipkow@13189
   760
    assume not0: "k \<noteq> 0"
nipkow@13189
   761
    with Q have R: ?R by simp
nipkow@13189
   762
    from not0 R[THEN spec,of "n div k",THEN spec, of "n mod k"]
nipkow@13517
   763
    show ?P by simp
nipkow@13189
   764
  qed
nipkow@13189
   765
qed
nipkow@13189
   766
berghofe@13882
   767
theorem mod_div_equality': "(m::nat) mod n = m - (m div n) * n"
berghofe@13882
   768
  apply (rule_tac P="%x. m mod n = x - (m div n) * n" in
berghofe@13882
   769
    subst [OF mod_div_equality [of _ n]])
berghofe@13882
   770
  apply arith
berghofe@13882
   771
  done
berghofe@13882
   772
haftmann@22800
   773
lemma div_mod_equality':
haftmann@22800
   774
  fixes m n :: nat
haftmann@22800
   775
  shows "m div n * n = m - m mod n"
haftmann@22800
   776
proof -
haftmann@22800
   777
  have "m mod n \<le> m mod n" ..
haftmann@22800
   778
  from div_mod_equality have 
haftmann@22800
   779
    "m div n * n + m mod n - m mod n = m - m mod n" by simp
haftmann@22800
   780
  with diff_add_assoc [OF `m mod n \<le> m mod n`, of "m div n * n"] have
haftmann@22800
   781
    "m div n * n + (m mod n - m mod n) = m - m mod n"
haftmann@22800
   782
    by simp
haftmann@22800
   783
  then show ?thesis by simp
haftmann@22800
   784
qed
haftmann@22800
   785
haftmann@22800
   786
paulson@14640
   787
subsection {*An ``induction'' law for modulus arithmetic.*}
paulson@14640
   788
paulson@14640
   789
lemma mod_induct_0:
paulson@14640
   790
  assumes step: "\<forall>i<p. P i \<longrightarrow> P ((Suc i) mod p)"
paulson@14640
   791
  and base: "P i" and i: "i<p"
paulson@14640
   792
  shows "P 0"
paulson@14640
   793
proof (rule ccontr)
paulson@14640
   794
  assume contra: "\<not>(P 0)"
paulson@14640
   795
  from i have p: "0<p" by simp
paulson@14640
   796
  have "\<forall>k. 0<k \<longrightarrow> \<not> P (p-k)" (is "\<forall>k. ?A k")
paulson@14640
   797
  proof
paulson@14640
   798
    fix k
paulson@14640
   799
    show "?A k"
paulson@14640
   800
    proof (induct k)
paulson@14640
   801
      show "?A 0" by simp  -- "by contradiction"
paulson@14640
   802
    next
paulson@14640
   803
      fix n
paulson@14640
   804
      assume ih: "?A n"
paulson@14640
   805
      show "?A (Suc n)"
paulson@14640
   806
      proof (clarsimp)
wenzelm@22718
   807
        assume y: "P (p - Suc n)"
wenzelm@22718
   808
        have n: "Suc n < p"
wenzelm@22718
   809
        proof (rule ccontr)
wenzelm@22718
   810
          assume "\<not>(Suc n < p)"
wenzelm@22718
   811
          hence "p - Suc n = 0"
wenzelm@22718
   812
            by simp
wenzelm@22718
   813
          with y contra show "False"
wenzelm@22718
   814
            by simp
wenzelm@22718
   815
        qed
wenzelm@22718
   816
        hence n2: "Suc (p - Suc n) = p-n" by arith
wenzelm@22718
   817
        from p have "p - Suc n < p" by arith
wenzelm@22718
   818
        with y step have z: "P ((Suc (p - Suc n)) mod p)"
wenzelm@22718
   819
          by blast
wenzelm@22718
   820
        show "False"
wenzelm@22718
   821
        proof (cases "n=0")
wenzelm@22718
   822
          case True
wenzelm@22718
   823
          with z n2 contra show ?thesis by simp
wenzelm@22718
   824
        next
wenzelm@22718
   825
          case False
wenzelm@22718
   826
          with p have "p-n < p" by arith
wenzelm@22718
   827
          with z n2 False ih show ?thesis by simp
wenzelm@22718
   828
        qed
paulson@14640
   829
      qed
paulson@14640
   830
    qed
paulson@14640
   831
  qed
paulson@14640
   832
  moreover
paulson@14640
   833
  from i obtain k where "0<k \<and> i+k=p"
paulson@14640
   834
    by (blast dest: less_imp_add_positive)
paulson@14640
   835
  hence "0<k \<and> i=p-k" by auto
paulson@14640
   836
  moreover
paulson@14640
   837
  note base
paulson@14640
   838
  ultimately
paulson@14640
   839
  show "False" by blast
paulson@14640
   840
qed
paulson@14640
   841
paulson@14640
   842
lemma mod_induct:
paulson@14640
   843
  assumes step: "\<forall>i<p. P i \<longrightarrow> P ((Suc i) mod p)"
paulson@14640
   844
  and base: "P i" and i: "i<p" and j: "j<p"
paulson@14640
   845
  shows "P j"
paulson@14640
   846
proof -
paulson@14640
   847
  have "\<forall>j<p. P j"
paulson@14640
   848
  proof
paulson@14640
   849
    fix j
paulson@14640
   850
    show "j<p \<longrightarrow> P j" (is "?A j")
paulson@14640
   851
    proof (induct j)
paulson@14640
   852
      from step base i show "?A 0"
wenzelm@22718
   853
        by (auto elim: mod_induct_0)
paulson@14640
   854
    next
paulson@14640
   855
      fix k
paulson@14640
   856
      assume ih: "?A k"
paulson@14640
   857
      show "?A (Suc k)"
paulson@14640
   858
      proof
wenzelm@22718
   859
        assume suc: "Suc k < p"
wenzelm@22718
   860
        hence k: "k<p" by simp
wenzelm@22718
   861
        with ih have "P k" ..
wenzelm@22718
   862
        with step k have "P (Suc k mod p)"
wenzelm@22718
   863
          by blast
wenzelm@22718
   864
        moreover
wenzelm@22718
   865
        from suc have "Suc k mod p = Suc k"
wenzelm@22718
   866
          by simp
wenzelm@22718
   867
        ultimately
wenzelm@22718
   868
        show "P (Suc k)" by simp
paulson@14640
   869
      qed
paulson@14640
   870
    qed
paulson@14640
   871
  qed
paulson@14640
   872
  with j show ?thesis by blast
paulson@14640
   873
qed
paulson@14640
   874
paulson@14640
   875
chaieb@18202
   876
lemma mod_add_left_eq: "((a::nat) + b) mod c = (a mod c + b) mod c"
chaieb@18202
   877
  apply (rule trans [symmetric])
wenzelm@22718
   878
   apply (rule mod_add1_eq, simp)
chaieb@18202
   879
  apply (rule mod_add1_eq [symmetric])
chaieb@18202
   880
  done
chaieb@18202
   881
chaieb@18202
   882
lemma mod_add_right_eq: "(a+b) mod (c::nat) = (a + (b mod c)) mod c"
wenzelm@22718
   883
  apply (rule trans [symmetric])
wenzelm@22718
   884
   apply (rule mod_add1_eq, simp)
wenzelm@22718
   885
  apply (rule mod_add1_eq [symmetric])
wenzelm@22718
   886
  done
chaieb@18202
   887
haftmann@22800
   888
lemma mod_div_decomp:
haftmann@22800
   889
  fixes n k :: nat
haftmann@22800
   890
  obtains m q where "m = n div k" and "q = n mod k"
haftmann@22800
   891
    and "n = m * k + q"
haftmann@22800
   892
proof -
haftmann@22800
   893
  from mod_div_equality have "n = n div k * k + n mod k" by auto
haftmann@22800
   894
  moreover have "n div k = n div k" ..
haftmann@22800
   895
  moreover have "n mod k = n mod k" ..
haftmann@22800
   896
  note that ultimately show thesis by blast
haftmann@22800
   897
qed
haftmann@22800
   898
haftmann@20589
   899
haftmann@22744
   900
subsection {* Code generation for div, mod and dvd on nat *}
haftmann@20589
   901
haftmann@22845
   902
definition [code func del]:
haftmann@20589
   903
  "divmod (m\<Colon>nat) n = (m div n, m mod n)"
haftmann@20589
   904
wenzelm@22718
   905
lemma divmod_zero [code]: "divmod m 0 = (0, m)"
haftmann@20589
   906
  unfolding divmod_def by simp
haftmann@20589
   907
haftmann@20589
   908
lemma divmod_succ [code]:
haftmann@20589
   909
  "divmod m (Suc k) = (if m < Suc k then (0, m) else
haftmann@20589
   910
    let
haftmann@20589
   911
      (p, q) = divmod (m - Suc k) (Suc k)
wenzelm@22718
   912
    in (Suc p, q))"
haftmann@20589
   913
  unfolding divmod_def Let_def split_def
haftmann@20589
   914
  by (auto intro: div_geq mod_geq)
haftmann@20589
   915
wenzelm@22718
   916
lemma div_divmod [code]: "m div n = fst (divmod m n)"
haftmann@20589
   917
  unfolding divmod_def by simp
haftmann@20589
   918
wenzelm@22718
   919
lemma mod_divmod [code]: "m mod n = snd (divmod m n)"
haftmann@20589
   920
  unfolding divmod_def by simp
haftmann@20589
   921
haftmann@22744
   922
definition
haftmann@22744
   923
  dvd_nat :: "nat \<Rightarrow> nat \<Rightarrow> bool"
haftmann@22744
   924
where
haftmann@22744
   925
  "dvd_nat m n \<longleftrightarrow> n mod m = (0 \<Colon> nat)"
haftmann@22744
   926
haftmann@22744
   927
lemma [code inline]:
haftmann@22744
   928
  "op dvd = dvd_nat"
haftmann@22744
   929
  by (auto simp add: dvd_nat_def dvd_eq_mod_eq_0 expand_fun_eq)
haftmann@22744
   930
haftmann@21191
   931
code_modulename SML
haftmann@21191
   932
  Divides Integer
haftmann@20640
   933
haftmann@21911
   934
code_modulename OCaml
haftmann@21911
   935
  Divides Integer
haftmann@21911
   936
haftmann@22744
   937
hide (open) const divmod dvd_nat
haftmann@20589
   938
haftmann@20589
   939
subsection {* Legacy bindings *}
haftmann@20589
   940
paulson@14267
   941
ML
paulson@14267
   942
{*
paulson@14267
   943
val div_def = thm "div_def"
paulson@14267
   944
val mod_def = thm "mod_def"
paulson@14267
   945
val dvd_def = thm "dvd_def"
paulson@14267
   946
val quorem_def = thm "quorem_def"
paulson@14267
   947
paulson@14267
   948
val wf_less_trans = thm "wf_less_trans";
paulson@14267
   949
val mod_eq = thm "mod_eq";
paulson@14267
   950
val div_eq = thm "div_eq";
paulson@14267
   951
val DIVISION_BY_ZERO_DIV = thm "DIVISION_BY_ZERO_DIV";
paulson@14267
   952
val DIVISION_BY_ZERO_MOD = thm "DIVISION_BY_ZERO_MOD";
paulson@14267
   953
val mod_less = thm "mod_less";
paulson@14267
   954
val mod_geq = thm "mod_geq";
paulson@14267
   955
val le_mod_geq = thm "le_mod_geq";
paulson@14267
   956
val mod_if = thm "mod_if";
paulson@14267
   957
val mod_1 = thm "mod_1";
paulson@14267
   958
val mod_self = thm "mod_self";
paulson@14267
   959
val mod_add_self2 = thm "mod_add_self2";
paulson@14267
   960
val mod_add_self1 = thm "mod_add_self1";
paulson@14267
   961
val mod_mult_self1 = thm "mod_mult_self1";
paulson@14267
   962
val mod_mult_self2 = thm "mod_mult_self2";
paulson@14267
   963
val mod_mult_distrib = thm "mod_mult_distrib";
paulson@14267
   964
val mod_mult_distrib2 = thm "mod_mult_distrib2";
paulson@14267
   965
val mod_mult_self_is_0 = thm "mod_mult_self_is_0";
paulson@14267
   966
val mod_mult_self1_is_0 = thm "mod_mult_self1_is_0";
paulson@14267
   967
val div_less = thm "div_less";
paulson@14267
   968
val div_geq = thm "div_geq";
paulson@14267
   969
val le_div_geq = thm "le_div_geq";
paulson@14267
   970
val div_if = thm "div_if";
paulson@14267
   971
val mod_div_equality = thm "mod_div_equality";
paulson@14267
   972
val mod_div_equality2 = thm "mod_div_equality2";
paulson@14267
   973
val div_mod_equality = thm "div_mod_equality";
paulson@14267
   974
val div_mod_equality2 = thm "div_mod_equality2";
paulson@14267
   975
val mult_div_cancel = thm "mult_div_cancel";
paulson@14267
   976
val mod_less_divisor = thm "mod_less_divisor";
paulson@14267
   977
val div_mult_self_is_m = thm "div_mult_self_is_m";
paulson@14267
   978
val div_mult_self1_is_m = thm "div_mult_self1_is_m";
paulson@14267
   979
val unique_quotient_lemma = thm "unique_quotient_lemma";
paulson@14267
   980
val unique_quotient = thm "unique_quotient";
paulson@14267
   981
val unique_remainder = thm "unique_remainder";
paulson@14267
   982
val div_0 = thm "div_0";
paulson@14267
   983
val mod_0 = thm "mod_0";
paulson@14267
   984
val div_mult1_eq = thm "div_mult1_eq";
paulson@14267
   985
val mod_mult1_eq = thm "mod_mult1_eq";
paulson@14267
   986
val mod_mult1_eq' = thm "mod_mult1_eq'";
paulson@14267
   987
val mod_mult_distrib_mod = thm "mod_mult_distrib_mod";
paulson@14267
   988
val div_add1_eq = thm "div_add1_eq";
paulson@14267
   989
val mod_add1_eq = thm "mod_add1_eq";
chaieb@18202
   990
val mod_add_left_eq = thm "mod_add_left_eq";
chaieb@18202
   991
 val mod_add_right_eq = thm "mod_add_right_eq";
paulson@14267
   992
val mod_lemma = thm "mod_lemma";
paulson@14267
   993
val div_mult2_eq = thm "div_mult2_eq";
paulson@14267
   994
val mod_mult2_eq = thm "mod_mult2_eq";
paulson@14267
   995
val div_mult_mult_lemma = thm "div_mult_mult_lemma";
paulson@14267
   996
val div_mult_mult1 = thm "div_mult_mult1";
paulson@14267
   997
val div_mult_mult2 = thm "div_mult_mult2";
paulson@14267
   998
val div_1 = thm "div_1";
paulson@14267
   999
val div_self = thm "div_self";
paulson@14267
  1000
val div_add_self2 = thm "div_add_self2";
paulson@14267
  1001
val div_add_self1 = thm "div_add_self1";
paulson@14267
  1002
val div_mult_self1 = thm "div_mult_self1";
paulson@14267
  1003
val div_mult_self2 = thm "div_mult_self2";
paulson@14267
  1004
val div_le_mono = thm "div_le_mono";
paulson@14267
  1005
val div_le_mono2 = thm "div_le_mono2";
paulson@14267
  1006
val div_le_dividend = thm "div_le_dividend";
paulson@14267
  1007
val div_less_dividend = thm "div_less_dividend";
paulson@14267
  1008
val mod_Suc = thm "mod_Suc";
paulson@14267
  1009
val dvdI = thm "dvdI";
paulson@14267
  1010
val dvdE = thm "dvdE";
paulson@14267
  1011
val dvd_0_right = thm "dvd_0_right";
paulson@14267
  1012
val dvd_0_left = thm "dvd_0_left";
paulson@14267
  1013
val dvd_0_left_iff = thm "dvd_0_left_iff";
paulson@14267
  1014
val dvd_1_left = thm "dvd_1_left";
paulson@14267
  1015
val dvd_1_iff_1 = thm "dvd_1_iff_1";
paulson@14267
  1016
val dvd_refl = thm "dvd_refl";
paulson@14267
  1017
val dvd_trans = thm "dvd_trans";
paulson@14267
  1018
val dvd_anti_sym = thm "dvd_anti_sym";
paulson@14267
  1019
val dvd_add = thm "dvd_add";
paulson@14267
  1020
val dvd_diff = thm "dvd_diff";
paulson@14267
  1021
val dvd_diffD = thm "dvd_diffD";
paulson@14267
  1022
val dvd_diffD1 = thm "dvd_diffD1";
paulson@14267
  1023
val dvd_mult = thm "dvd_mult";
paulson@14267
  1024
val dvd_mult2 = thm "dvd_mult2";
paulson@14267
  1025
val dvd_reduce = thm "dvd_reduce";
paulson@14267
  1026
val dvd_mod = thm "dvd_mod";
paulson@14267
  1027
val dvd_mod_imp_dvd = thm "dvd_mod_imp_dvd";
paulson@14267
  1028
val dvd_mod_iff = thm "dvd_mod_iff";
paulson@14267
  1029
val dvd_mult_cancel = thm "dvd_mult_cancel";
paulson@14267
  1030
val dvd_mult_cancel1 = thm "dvd_mult_cancel1";
paulson@14267
  1031
val dvd_mult_cancel2 = thm "dvd_mult_cancel2";
paulson@14267
  1032
val mult_dvd_mono = thm "mult_dvd_mono";
paulson@14267
  1033
val dvd_mult_left = thm "dvd_mult_left";
paulson@14267
  1034
val dvd_mult_right = thm "dvd_mult_right";
paulson@14267
  1035
val dvd_imp_le = thm "dvd_imp_le";
paulson@14267
  1036
val dvd_eq_mod_eq_0 = thm "dvd_eq_mod_eq_0";
paulson@14267
  1037
val dvd_mult_div_cancel = thm "dvd_mult_div_cancel";
paulson@14267
  1038
val mod_eq_0_iff = thm "mod_eq_0_iff";
paulson@14267
  1039
val mod_eqD = thm "mod_eqD";
paulson@14267
  1040
*}
paulson@14267
  1041
nipkow@13189
  1042
(*
nipkow@13189
  1043
lemma split_div:
nipkow@13152
  1044
assumes m: "m \<noteq> 0"
nipkow@13152
  1045
shows "P(n div m :: nat) = (!i. !j<m. n = m*i + j \<longrightarrow> P i)"
nipkow@13152
  1046
       (is "?P = ?Q")
nipkow@13152
  1047
proof
nipkow@13152
  1048
  assume P: ?P
nipkow@13152
  1049
  show ?Q
nipkow@13152
  1050
  proof (intro allI impI)
nipkow@13152
  1051
    fix i j
nipkow@13152
  1052
    assume n: "n = m*i + j" and j: "j < m"
nipkow@13152
  1053
    show "P i"
nipkow@13152
  1054
    proof (cases)
nipkow@13152
  1055
      assume "i = 0"
nipkow@13152
  1056
      with n j P show "P i" by simp
nipkow@13152
  1057
    next
nipkow@13152
  1058
      assume "i \<noteq> 0"
nipkow@13152
  1059
      with n j P show "P i" by (simp add:add_ac div_mult_self1)
nipkow@13152
  1060
    qed
nipkow@13152
  1061
  qed
nipkow@13152
  1062
next
nipkow@13152
  1063
  assume Q: ?Q
nipkow@13152
  1064
  from m Q[THEN spec,of "n div m",THEN spec, of "n mod m"]
nipkow@13517
  1065
  show ?P by simp
nipkow@13152
  1066
qed
nipkow@13152
  1067
nipkow@13152
  1068
lemma split_mod:
nipkow@13152
  1069
assumes m: "m \<noteq> 0"
nipkow@13152
  1070
shows "P(n mod m :: nat) = (!i. !j<m. n = m*i + j \<longrightarrow> P j)"
nipkow@13152
  1071
       (is "?P = ?Q")
nipkow@13152
  1072
proof
nipkow@13152
  1073
  assume P: ?P
nipkow@13152
  1074
  show ?Q
nipkow@13152
  1075
  proof (intro allI impI)
nipkow@13152
  1076
    fix i j
nipkow@13152
  1077
    assume "n = m*i + j" "j < m"
nipkow@13152
  1078
    thus "P j" using m P by(simp add:add_ac mult_ac)
nipkow@13152
  1079
  qed
nipkow@13152
  1080
next
nipkow@13152
  1081
  assume Q: ?Q
nipkow@13152
  1082
  from m Q[THEN spec,of "n div m",THEN spec, of "n mod m"]
nipkow@13517
  1083
  show ?P by simp
nipkow@13152
  1084
qed
nipkow@13189
  1085
*)
paulson@3366
  1086
end