src/CTT/Arith.thy
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(*  Title:      CTT/Arith.thy
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    Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
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    Copyright   1991  University of Cambridge
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*)
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section {* Elementary arithmetic *}
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theory Arith
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imports Bool
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begin
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subsection {* Arithmetic operators and their definitions *}
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definition
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  add :: "[i,i]\<Rightarrow>i"   (infixr "#+" 65) where
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  "a#+b == rec(a, b, \<lambda>u v. succ(v))"
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definition
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  diff :: "[i,i]\<Rightarrow>i"   (infixr "-" 65) where
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  "a-b == rec(b, a, \<lambda>u v. rec(v, 0, \<lambda>x y. x))"
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definition
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  absdiff :: "[i,i]\<Rightarrow>i"   (infixr "|-|" 65) where
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  "a|-|b == (a-b) #+ (b-a)"
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definition
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  mult :: "[i,i]\<Rightarrow>i"   (infixr "#*" 70) where
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  "a#*b == rec(a, 0, \<lambda>u v. b #+ v)"
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definition
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  mod :: "[i,i]\<Rightarrow>i"   (infixr "mod" 70) where
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  "a mod b == rec(a, 0, %u v. rec(succ(v) |-| b, 0, %x y. succ(v)))"
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definition
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  div :: "[i,i]\<Rightarrow>i"   (infixr "div" 70) where
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  "a div b == rec(a, 0, \<lambda>u v. rec(succ(u) mod b, succ(v), \<lambda>x y. v))"
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notation (xsymbols)
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  mult  (infixr "#\<times>" 70)
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notation (HTML output)
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  mult (infixr "#\<times>" 70)
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lemmas arith_defs = add_def diff_def absdiff_def mult_def mod_def div_def
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subsection {* Proofs about elementary arithmetic: addition, multiplication, etc. *}
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(** Addition *)
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(*typing of add: short and long versions*)
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lemma add_typing: "\<lbrakk>a:N; b:N\<rbrakk> \<Longrightarrow> a #+ b : N"
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apply (unfold arith_defs)
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apply typechk
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done
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lemma add_typingL: "\<lbrakk>a = c:N; b = d:N\<rbrakk> \<Longrightarrow> a #+ b = c #+ d : N"
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apply (unfold arith_defs)
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apply equal
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done
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(*computation for add: 0 and successor cases*)
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lemma addC0: "b:N \<Longrightarrow> 0 #+ b = b : N"
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apply (unfold arith_defs)
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apply rew
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done
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lemma addC_succ: "\<lbrakk>a:N; b:N\<rbrakk> \<Longrightarrow> succ(a) #+ b = succ(a #+ b) : N"
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apply (unfold arith_defs)
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apply rew
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done
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(** Multiplication *)
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(*typing of mult: short and long versions*)
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lemma mult_typing: "\<lbrakk>a:N; b:N\<rbrakk> \<Longrightarrow> a #* b : N"
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apply (unfold arith_defs)
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apply (typechk add_typing)
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done
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lemma mult_typingL: "\<lbrakk>a = c:N; b = d:N\<rbrakk> \<Longrightarrow> a #* b = c #* d : N"
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apply (unfold arith_defs)
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apply (equal add_typingL)
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done
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(*computation for mult: 0 and successor cases*)
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lemma multC0: "b:N \<Longrightarrow> 0 #* b = 0 : N"
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apply (unfold arith_defs)
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apply rew
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done
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lemma multC_succ: "\<lbrakk>a:N; b:N\<rbrakk> \<Longrightarrow> succ(a) #* b = b #+ (a #* b) : N"
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apply (unfold arith_defs)
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apply rew
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done
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(** Difference *)
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(*typing of difference*)
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lemma diff_typing: "\<lbrakk>a:N; b:N\<rbrakk> \<Longrightarrow> a - b : N"
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apply (unfold arith_defs)
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apply typechk
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done
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lemma diff_typingL: "\<lbrakk>a = c:N; b = d:N\<rbrakk> \<Longrightarrow> a - b = c - d : N"
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apply (unfold arith_defs)
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apply equal
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done
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(*computation for difference: 0 and successor cases*)
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lemma diffC0: "a:N \<Longrightarrow> a - 0 = a : N"
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apply (unfold arith_defs)
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apply rew
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done
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(*Note: rec(a, 0, \<lambda>z w.z) is pred(a). *)
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lemma diff_0_eq_0: "b:N \<Longrightarrow> 0 - b = 0 : N"
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apply (unfold arith_defs)
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apply (NE b)
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apply hyp_rew
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done
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(*Essential to simplify FIRST!!  (Else we get a critical pair)
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  succ(a) - succ(b) rewrites to   pred(succ(a) - b)  *)
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lemma diff_succ_succ: "\<lbrakk>a:N; b:N\<rbrakk> \<Longrightarrow> succ(a) - succ(b) = a - b : N"
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apply (unfold arith_defs)
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apply hyp_rew
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apply (NE b)
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apply hyp_rew
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done
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subsection {* Simplification *}
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lemmas arith_typing_rls = add_typing mult_typing diff_typing
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  and arith_congr_rls = add_typingL mult_typingL diff_typingL
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lemmas congr_rls = arith_congr_rls intrL2_rls elimL_rls
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lemmas arithC_rls =
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  addC0 addC_succ
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  multC0 multC_succ
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  diffC0 diff_0_eq_0 diff_succ_succ
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ML {*
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structure Arith_simp_data: TSIMP_DATA =
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  struct
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  val refl              = @{thm refl_elem}
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  val sym               = @{thm sym_elem}
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  val trans             = @{thm trans_elem}
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  val refl_red          = @{thm refl_red}
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  val trans_red         = @{thm trans_red}
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  val red_if_equal      = @{thm red_if_equal}
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  val default_rls       = @{thms arithC_rls} @ @{thms comp_rls}
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  val routine_tac       = routine_tac (@{thms arith_typing_rls} @ @{thms routine_rls})
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  end
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structure Arith_simp = TSimpFun (Arith_simp_data)
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local val congr_rls = @{thms congr_rls} in
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fun arith_rew_tac ctxt prems = make_rew_tac ctxt
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  (Arith_simp.norm_tac ctxt (congr_rls, prems))
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fun hyp_arith_rew_tac ctxt prems = make_rew_tac ctxt
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  (Arith_simp.cond_norm_tac ctxt (prove_cond_tac ctxt, congr_rls, prems))
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0
a5a9c433f639 Initial revision
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end
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*}
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method_setup arith_rew = {*
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  Attrib.thms >> (fn ths => fn ctxt => SIMPLE_METHOD (arith_rew_tac ctxt ths))
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*}
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method_setup hyp_arith_rew = {*
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  Attrib.thms >> (fn ths => fn ctxt => SIMPLE_METHOD (hyp_arith_rew_tac ctxt ths))
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*}
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subsection {* Addition *}
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(*Associative law for addition*)
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lemma add_assoc: "\<lbrakk>a:N; b:N; c:N\<rbrakk> \<Longrightarrow> (a #+ b) #+ c = a #+ (b #+ c) : N"
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apply (NE a)
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apply hyp_arith_rew
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done
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(*Commutative law for addition.  Can be proved using three inductions.
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  Must simplify after first induction!  Orientation of rewrites is delicate*)
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lemma add_commute: "\<lbrakk>a:N; b:N\<rbrakk> \<Longrightarrow> a #+ b = b #+ a : N"
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apply (NE a)
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apply hyp_arith_rew
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apply (rule sym_elem)
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prefer 2
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apply (NE b)
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prefer 4
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apply (NE b)
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apply hyp_arith_rew
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done
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subsection {* Multiplication *}
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(*right annihilation in product*)
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lemma mult_0_right: "a:N \<Longrightarrow> a #* 0 = 0 : N"
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apply (NE a)
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apply hyp_arith_rew
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done
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(*right successor law for multiplication*)
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lemma mult_succ_right: "\<lbrakk>a:N; b:N\<rbrakk> \<Longrightarrow> a #* succ(b) = a #+ (a #* b) : N"
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apply (NE a)
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apply (hyp_arith_rew add_assoc [THEN sym_elem])
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apply (assumption | rule add_commute mult_typingL add_typingL intrL_rls refl_elem)+
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done
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(*Commutative law for multiplication*)
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lemma mult_commute: "\<lbrakk>a:N; b:N\<rbrakk> \<Longrightarrow> a #* b = b #* a : N"
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apply (NE a)
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apply (hyp_arith_rew mult_0_right mult_succ_right)
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done
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(*addition distributes over multiplication*)
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lemma add_mult_distrib: "\<lbrakk>a:N; b:N; c:N\<rbrakk> \<Longrightarrow> (a #+ b) #* c = (a #* c) #+ (b #* c) : N"
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apply (NE a)
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apply (hyp_arith_rew add_assoc [THEN sym_elem])
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done
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(*Associative law for multiplication*)
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lemma mult_assoc: "\<lbrakk>a:N; b:N; c:N\<rbrakk> \<Longrightarrow> (a #* b) #* c = a #* (b #* c) : N"
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apply (NE a)
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apply (hyp_arith_rew add_mult_distrib)
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done
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subsection {* Difference *}
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text {*
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Difference on natural numbers, without negative numbers
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  a - b = 0  iff  a<=b    a - b = succ(c) iff a>b   *}
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lemma diff_self_eq_0: "a:N \<Longrightarrow> a - a = 0 : N"
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apply (NE a)
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apply hyp_arith_rew
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done
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lemma add_0_right: "\<lbrakk>c : N; 0 : N; c : N\<rbrakk> \<Longrightarrow> c #+ 0 = c : N"
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  by (rule addC0 [THEN [3] add_commute [THEN trans_elem]])
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(*Addition is the inverse of subtraction: if b<=x then b#+(x-b) = x.
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  An example of induction over a quantified formula (a product).
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  Uses rewriting with a quantified, implicative inductive hypothesis.*)
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schematic_lemma add_diff_inverse_lemma:
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  "b:N \<Longrightarrow> ?a : PROD x:N. Eq(N, b-x, 0) --> Eq(N, b #+ (x-b), x)"
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apply (NE b)
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(*strip one "universal quantifier" but not the "implication"*)
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apply (rule_tac [3] intr_rls)
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(*case analysis on x in
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    (succ(u) <= x) --> (succ(u)#+(x-succ(u)) = x) *)
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prefer 4
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apply (NE x)
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apply assumption
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(*Prepare for simplification of types -- the antecedent succ(u)<=x *)
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apply (rule_tac [2] replace_type)
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apply (rule_tac [1] replace_type)
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apply arith_rew
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(*Solves first 0 goal, simplifies others.  Two sugbgoals remain.
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  Both follow by rewriting, (2) using quantified induction hyp*)
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apply intr (*strips remaining PRODs*)
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apply (hyp_arith_rew add_0_right)
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apply assumption
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done
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(*Version of above with premise   b-a=0   i.e.    a >= b.
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  Using ProdE does not work -- for ?B(?a) is ambiguous.
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  Instead, add_diff_inverse_lemma states the desired induction scheme
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    the use of RS below instantiates Vars in ProdE automatically. *)
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lemma add_diff_inverse: "\<lbrakk>a:N; b:N; b - a = 0 : N\<rbrakk> \<Longrightarrow> b #+ (a-b) = a : N"
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apply (rule EqE)
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apply (rule add_diff_inverse_lemma [THEN ProdE, THEN ProdE])
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apply (assumption | rule EqI)+
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done
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subsection {* Absolute difference *}
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(*typing of absolute difference: short and long versions*)
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lemma absdiff_typing: "\<lbrakk>a:N; b:N\<rbrakk> \<Longrightarrow> a |-| b : N"
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apply (unfold arith_defs)
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apply typechk
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done
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lemma absdiff_typingL: "\<lbrakk>a = c:N; b = d:N\<rbrakk> \<Longrightarrow> a |-| b = c |-| d : N"
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apply (unfold arith_defs)
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apply equal
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done
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lemma absdiff_self_eq_0: "a:N \<Longrightarrow> a |-| a = 0 : N"
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apply (unfold absdiff_def)
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apply (arith_rew diff_self_eq_0)
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done
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lemma absdiffC0: "a:N \<Longrightarrow> 0 |-| a = a : N"
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apply (unfold absdiff_def)
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apply hyp_arith_rew
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done
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lemma absdiff_succ_succ: "\<lbrakk>a:N; b:N\<rbrakk> \<Longrightarrow> succ(a) |-| succ(b)  =  a |-| b : N"
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apply (unfold absdiff_def)
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apply hyp_arith_rew
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done
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(*Note how easy using commutative laws can be?  ...not always... *)
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lemma absdiff_commute: "\<lbrakk>a:N; b:N\<rbrakk> \<Longrightarrow> a |-| b = b |-| a : N"
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apply (unfold absdiff_def)
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   335
apply (rule add_commute)
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   336
apply (typechk diff_typing)
19761
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   337
done
5cd82054c2c6 removed obsolete ML files;
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   338
5cd82054c2c6 removed obsolete ML files;
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   339
(*If a+b=0 then a=0.   Surprisingly tedious*)
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   340
schematic_lemma add_eq0_lemma: "\<lbrakk>a:N; b:N\<rbrakk> \<Longrightarrow> ?c : PROD u: Eq(N,a#+b,0) .  Eq(N,a,0)"
58972
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   341
apply (NE a)
19761
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   342
apply (rule_tac [3] replace_type)
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   343
apply arith_rew
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   344
apply intr (*strips remaining PRODs*)
19761
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   345
apply (rule_tac [2] zero_ne_succ [THEN FE])
5cd82054c2c6 removed obsolete ML files;
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   346
apply (erule_tac [3] EqE [THEN sym_elem])
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   347
apply (typechk add_typing)
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   348
done
5cd82054c2c6 removed obsolete ML files;
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   349
5cd82054c2c6 removed obsolete ML files;
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   350
(*Version of above with the premise  a+b=0.
5cd82054c2c6 removed obsolete ML files;
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   351
  Again, resolution instantiates variables in ProdE *)
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   352
lemma add_eq0: "\<lbrakk>a:N; b:N; a #+ b = 0 : N\<rbrakk> \<Longrightarrow> a = 0 : N"
19761
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   353
apply (rule EqE)
5cd82054c2c6 removed obsolete ML files;
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   354
apply (rule add_eq0_lemma [THEN ProdE])
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   355
apply (rule_tac [3] EqI)
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   356
apply typechk
19761
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   357
done
5cd82054c2c6 removed obsolete ML files;
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   358
5cd82054c2c6 removed obsolete ML files;
wenzelm
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diff changeset
   359
(*Here is a lemma to infer a-b=0 and b-a=0 from a|-|b=0, below. *)
36319
8feb2c4bef1a mark schematic statements explicitly;
wenzelm
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diff changeset
   360
schematic_lemma absdiff_eq0_lem:
58977
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diff changeset
   361
  "\<lbrakk>a:N; b:N; a |-| b = 0 : N\<rbrakk> \<Longrightarrow> ?a : SUM v: Eq(N, a-b, 0) . Eq(N, b-a, 0)"
19761
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   362
apply (unfold absdiff_def)
58972
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   363
apply intr
5b026cfc5f04 more Isar proof methods;
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diff changeset
   364
apply eqintr
19761
5cd82054c2c6 removed obsolete ML files;
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diff changeset
   365
apply (rule_tac [2] add_eq0)
5cd82054c2c6 removed obsolete ML files;
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   366
apply (rule add_eq0)
5cd82054c2c6 removed obsolete ML files;
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   367
apply (rule_tac [6] add_commute [THEN trans_elem])
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   368
apply (typechk diff_typing)
19761
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   369
done
5cd82054c2c6 removed obsolete ML files;
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   370
5cd82054c2c6 removed obsolete ML files;
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   371
(*if  a |-| b = 0  then  a = b
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  proof: a-b=0 and b-a=0, so b = a+(b-a) = a+0 = a*)
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   373
lemma absdiff_eq0: "\<lbrakk>a |-| b = 0 : N; a:N; b:N\<rbrakk> \<Longrightarrow> a = b : N"
19761
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   374
apply (rule EqE)
5cd82054c2c6 removed obsolete ML files;
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   375
apply (rule absdiff_eq0_lem [THEN SumE])
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   376
apply eqintr
19761
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diff changeset
   377
apply (rule add_diff_inverse [THEN sym_elem, THEN trans_elem])
58972
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wenzelm
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diff changeset
   378
apply (erule_tac [3] EqE)
5b026cfc5f04 more Isar proof methods;
wenzelm
parents: 58963
diff changeset
   379
apply (hyp_arith_rew add_0_right)
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   380
done
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   381
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   382
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   383
subsection {* Remainder and Quotient *}
5cd82054c2c6 removed obsolete ML files;
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diff changeset
   384
5cd82054c2c6 removed obsolete ML files;
wenzelm
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diff changeset
   385
(*typing of remainder: short and long versions*)
5cd82054c2c6 removed obsolete ML files;
wenzelm
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diff changeset
   386
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   387
lemma mod_typing: "\<lbrakk>a:N; b:N\<rbrakk> \<Longrightarrow> a mod b : N"
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   388
apply (unfold mod_def)
58972
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wenzelm
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diff changeset
   389
apply (typechk absdiff_typing)
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   390
done
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   391
58977
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diff changeset
   392
lemma mod_typingL: "\<lbrakk>a = c:N; b = d:N\<rbrakk> \<Longrightarrow> a mod b = c mod d : N"
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   393
apply (unfold mod_def)
58972
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diff changeset
   394
apply (equal absdiff_typingL)
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   395
done
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   396
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   397
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   398
(*computation for  mod : 0 and successor cases*)
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   399
58977
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   400
lemma modC0: "b:N \<Longrightarrow> 0 mod b = 0 : N"
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   401
apply (unfold mod_def)
58972
5b026cfc5f04 more Isar proof methods;
wenzelm
parents: 58963
diff changeset
   402
apply (rew absdiff_typing)
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   403
done
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   404
58977
9576b510f6a2 more symbols;
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parents: 58976
diff changeset
   405
lemma modC_succ: "\<lbrakk>a:N; b:N\<rbrakk> \<Longrightarrow>
9576b510f6a2 more symbols;
wenzelm
parents: 58976
diff changeset
   406
  succ(a) mod b = rec(succ(a mod b) |-| b, 0, \<lambda>x y. succ(a mod b)) : N"
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   407
apply (unfold mod_def)
58972
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wenzelm
parents: 58963
diff changeset
   408
apply (rew absdiff_typing)
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   409
done
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   410
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   411
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   412
(*typing of quotient: short and long versions*)
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   413
58977
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parents: 58976
diff changeset
   414
lemma div_typing: "\<lbrakk>a:N; b:N\<rbrakk> \<Longrightarrow> a div b : N"
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   415
apply (unfold div_def)
58972
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wenzelm
parents: 58963
diff changeset
   416
apply (typechk absdiff_typing mod_typing)
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   417
done
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   418
58977
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wenzelm
parents: 58976
diff changeset
   419
lemma div_typingL: "\<lbrakk>a = c:N; b = d:N\<rbrakk> \<Longrightarrow> a div b = c div d : N"
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   420
apply (unfold div_def)
58972
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wenzelm
parents: 58963
diff changeset
   421
apply (equal absdiff_typingL mod_typingL)
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   422
done
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   423
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   424
lemmas div_typing_rls = mod_typing div_typing absdiff_typing
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   425
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   426
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   427
(*computation for quotient: 0 and successor cases*)
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   428
58977
9576b510f6a2 more symbols;
wenzelm
parents: 58976
diff changeset
   429
lemma divC0: "b:N \<Longrightarrow> 0 div b = 0 : N"
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   430
apply (unfold div_def)
58972
5b026cfc5f04 more Isar proof methods;
wenzelm
parents: 58963
diff changeset
   431
apply (rew mod_typing absdiff_typing)
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   432
done
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   433
58977
9576b510f6a2 more symbols;
wenzelm
parents: 58976
diff changeset
   434
lemma divC_succ: "\<lbrakk>a:N; b:N\<rbrakk> \<Longrightarrow>
9576b510f6a2 more symbols;
wenzelm
parents: 58976
diff changeset
   435
  succ(a) div b = rec(succ(a) mod b, succ(a div b), \<lambda>x y. a div b) : N"
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   436
apply (unfold div_def)
58972
5b026cfc5f04 more Isar proof methods;
wenzelm
parents: 58963
diff changeset
   437
apply (rew mod_typing)
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   438
done
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   439
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   440
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   441
(*Version of above with same condition as the  mod  one*)
58977
9576b510f6a2 more symbols;
wenzelm
parents: 58976
diff changeset
   442
lemma divC_succ2: "\<lbrakk>a:N; b:N\<rbrakk> \<Longrightarrow>
9576b510f6a2 more symbols;
wenzelm
parents: 58976
diff changeset
   443
  succ(a) div b =rec(succ(a mod b) |-| b, succ(a div b), \<lambda>x y. a div b) : N"
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   444
apply (rule divC_succ [THEN trans_elem])
58972
5b026cfc5f04 more Isar proof methods;
wenzelm
parents: 58963
diff changeset
   445
apply (rew div_typing_rls modC_succ)
5b026cfc5f04 more Isar proof methods;
wenzelm
parents: 58963
diff changeset
   446
apply (NE "succ (a mod b) |-|b")
5b026cfc5f04 more Isar proof methods;
wenzelm
parents: 58963
diff changeset
   447
apply (rew mod_typing div_typing absdiff_typing)
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   448
done
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   449
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   450
(*for case analysis on whether a number is 0 or a successor*)
58977
9576b510f6a2 more symbols;
wenzelm
parents: 58976
diff changeset
   451
lemma iszero_decidable: "a:N \<Longrightarrow> rec(a, inl(eq), \<lambda>ka kb. inr(<ka, eq>)) :
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   452
                      Eq(N,a,0) + (SUM x:N. Eq(N,a, succ(x)))"
58972
5b026cfc5f04 more Isar proof methods;
wenzelm
parents: 58963
diff changeset
   453
apply (NE a)
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   454
apply (rule_tac [3] PlusI_inr)
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   455
apply (rule_tac [2] PlusI_inl)
58972
5b026cfc5f04 more Isar proof methods;
wenzelm
parents: 58963
diff changeset
   456
apply eqintr
5b026cfc5f04 more Isar proof methods;
wenzelm
parents: 58963
diff changeset
   457
apply equal
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   458
done
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   459
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   460
(*Main Result.  Holds when b is 0 since   a mod 0 = a     and    a div 0 = 0  *)
58977
9576b510f6a2 more symbols;
wenzelm
parents: 58976
diff changeset
   461
lemma mod_div_equality: "\<lbrakk>a:N; b:N\<rbrakk> \<Longrightarrow> a mod b #+ (a div b) #* b = a : N"
58972
5b026cfc5f04 more Isar proof methods;
wenzelm
parents: 58963
diff changeset
   462
apply (NE a)
5b026cfc5f04 more Isar proof methods;
wenzelm
parents: 58963
diff changeset
   463
apply (arith_rew div_typing_rls modC0 modC_succ divC0 divC_succ2)
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   464
apply (rule EqE)
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   465
(*case analysis on   succ(u mod b)|-|b  *)
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   466
apply (rule_tac a1 = "succ (u mod b) |-| b" in iszero_decidable [THEN PlusE])
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   467
apply (erule_tac [3] SumE)
58972
5b026cfc5f04 more Isar proof methods;
wenzelm
parents: 58963
diff changeset
   468
apply (hyp_arith_rew div_typing_rls modC0 modC_succ divC0 divC_succ2)
58318
f95754ca7082 fixed some spelling mistakes
blanchet
parents: 39159
diff changeset
   469
(*Replace one occurrence of  b  by succ(u mod b).  Clumsy!*)
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   470
apply (rule add_typingL [THEN trans_elem])
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   471
apply (erule EqE [THEN absdiff_eq0, THEN sym_elem])
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   472
apply (rule_tac [3] refl_elem)
58972
5b026cfc5f04 more Isar proof methods;
wenzelm
parents: 58963
diff changeset
   473
apply (hyp_arith_rew div_typing_rls)
19761
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   474
done
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   475
5cd82054c2c6 removed obsolete ML files;
wenzelm
parents: 17441
diff changeset
   476
end