src/HOL/NSA/Star.thy

remove historical bloat -- another benefit of merging Metis's and Sledgehammer's translations

+
−(*  Title       : Star.thy
+
−    Author      : Jacques D. Fleuriot
+
−    Copyright   : 1998  University of Cambridge
+
−    Conversion to Isar and new proofs by Lawrence C Paulson, 2003/4
+
−*)
+
−
+
−header{*Star-Transforms in Non-Standard Analysis*}
+
−
+
−theory Star
+
−imports NSA
+
−begin
+
−
+
−definition
+
−    (* internal sets *)
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−  starset_n :: "(nat => 'a set) => 'a star set" ("*sn* _" [80] 80) where
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−  "*sn* As = Iset (star_n As)"
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−
+
−definition
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−  InternalSets :: "'a star set set" where
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−  "InternalSets = {X. \<exists>As. X = *sn* As}"
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−
+
−definition
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−  (* nonstandard extension of function *)
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−  is_starext  :: "['a star => 'a star, 'a => 'a] => bool" where
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−  "is_starext F f = (\<forall>x y. \<exists>X \<in> Rep_star(x). \<exists>Y \<in> Rep_star(y).
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−                        ((y = (F x)) = ({n. Y n = f(X n)} : FreeUltrafilterNat)))"
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−
+
−definition
+
−  (* internal functions *)
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−  starfun_n :: "(nat => ('a => 'b)) => 'a star => 'b star"   ("*fn* _" [80] 80) where
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−  "*fn* F = Ifun (star_n F)"
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−
+
−definition
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−  InternalFuns :: "('a star => 'b star) set" where
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−  "InternalFuns = {X. \<exists>F. X = *fn* F}"
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−
+
−
+
−(*--------------------------------------------------------
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−   Preamble - Pulling "EX" over "ALL"
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− ---------------------------------------------------------*)
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−
+
−(* This proof does not need AC and was suggested by the
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−   referee for the JCM Paper: let f(x) be least y such
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−   that  Q(x,y)
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−*)
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−lemma no_choice: "\<forall>x. \<exists>y. Q x y ==> \<exists>(f :: 'a => nat). \<forall>x. Q x (f x)"
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−apply (rule_tac x = "%x. LEAST y. Q x y" in exI)
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−apply (blast intro: LeastI)
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−done
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−
+
−subsection{*Properties of the Star-transform Applied to Sets of Reals*}
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−
+
−lemma STAR_star_of_image_subset: "star_of ` A <= *s* A"
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−by auto
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−
+
−lemma STAR_hypreal_of_real_Int: "*s* X Int Reals = hypreal_of_real ` X"
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−by (auto simp add: SReal_def)
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−
+
−lemma STAR_star_of_Int: "*s* X Int Standard = star_of ` X"
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−by (auto simp add: Standard_def)
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−
+
−lemma lemma_not_hyprealA: "x \<notin> hypreal_of_real ` A ==> \<forall>y \<in> A. x \<noteq> hypreal_of_real y"
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−by auto
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−
+
−lemma lemma_not_starA: "x \<notin> star_of ` A ==> \<forall>y \<in> A. x \<noteq> star_of y"
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−by auto
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−
+
−lemma lemma_Compl_eq: "- {n. X n = xa} = {n. X n \<noteq> xa}"
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−by auto
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−
+
−lemma STAR_real_seq_to_hypreal:
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−    "\<forall>n. (X n) \<notin> M ==> star_n X \<notin> *s* M"
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−apply (unfold starset_def star_of_def)
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−apply (simp add: Iset_star_n)
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−done
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−
+
−lemma STAR_singleton: "*s* {x} = {star_of x}"
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−by simp
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−
+
−lemma STAR_not_mem: "x \<notin> F ==> star_of x \<notin> *s* F"
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−by transfer
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−
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−lemma STAR_subset_closed: "[| x : *s* A; A <= B |] ==> x : *s* B"
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−by (erule rev_subsetD, simp)
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−
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−text{*Nonstandard extension of a set (defined using a constant
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−   sequence) as a special case of an internal set*}
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−
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−lemma starset_n_starset: "\<forall>n. (As n = A) ==> *sn* As = *s* A"
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−apply (drule fun_eq_iff [THEN iffD2])
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−apply (simp add: starset_n_def starset_def star_of_def)
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−done
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−
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−
+
−(*----------------------------------------------------------------*)
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−(* Theorems about nonstandard extensions of functions             *)
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−(*----------------------------------------------------------------*)
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−
+
−(*----------------------------------------------------------------*)
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−(* Nonstandard extension of a function (defined using a           *)
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−(* constant sequence) as a special case of an internal function   *)
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−(*----------------------------------------------------------------*)
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−
+
−lemma starfun_n_starfun: "\<forall>n. (F n = f) ==> *fn* F = *f* f"
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−apply (drule fun_eq_iff [THEN iffD2])
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−apply (simp add: starfun_n_def starfun_def star_of_def)
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−done
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−
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−
+
−(*
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−   Prove that abs for hypreal is a nonstandard extension of abs for real w/o
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−   use of congruence property (proved after this for general
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−   nonstandard extensions of real valued functions). 
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−
+
−   Proof now Uses the ultrafilter tactic!
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−*)
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−
+
−lemma hrabs_is_starext_rabs: "is_starext abs abs"
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−apply (simp add: is_starext_def, safe)
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−apply (rule_tac x=x in star_cases)
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−apply (rule_tac x=y in star_cases)
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−apply (unfold star_n_def, auto)
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−apply (rule bexI, rule_tac [2] lemma_starrel_refl)
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−apply (rule bexI, rule_tac [2] lemma_starrel_refl)
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−apply (fold star_n_def)
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−apply (unfold star_abs_def starfun_def star_of_def)
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−apply (simp add: Ifun_star_n star_n_eq_iff)
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−done
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−
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−text{*Nonstandard extension of functions*}
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−
+
−lemma starfun:
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−      "( *f* f) (star_n X) = star_n (%n. f (X n))"
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−by (rule starfun_star_n)
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−
+
−lemma starfun_if_eq:
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−     "!!w. w \<noteq> star_of x
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−       ==> ( *f* (\<lambda>z. if z = x then a else g z)) w = ( *f* g) w"
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−by (transfer, simp)
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−
+
−(*-------------------------------------------
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−  multiplication: ( *f) x ( *g) = *(f x g)
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− ------------------------------------------*)
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−lemma starfun_mult: "!!x. ( *f* f) x * ( *f* g) x = ( *f* (%x. f x * g x)) x"
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−by (transfer, rule refl)
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−declare starfun_mult [symmetric, simp]
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−
+
−(*---------------------------------------
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−  addition: ( *f) + ( *g) = *(f + g)
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− ---------------------------------------*)
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−lemma starfun_add: "!!x. ( *f* f) x + ( *f* g) x = ( *f* (%x. f x + g x)) x"
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−by (transfer, rule refl)
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−declare starfun_add [symmetric, simp]
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−
+
−(*--------------------------------------------
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−  subtraction: ( *f) + -( *g) = *(f + -g)
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− -------------------------------------------*)
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−lemma starfun_minus: "!!x. - ( *f* f) x = ( *f* (%x. - f x)) x"
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−by (transfer, rule refl)
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−declare starfun_minus [symmetric, simp]
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−
+
−(*FIXME: delete*)
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−lemma starfun_add_minus: "!!x. ( *f* f) x + -( *f* g) x = ( *f* (%x. f x + -g x)) x"
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−by (transfer, rule refl)
+
−declare starfun_add_minus [symmetric, simp]
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−
+
−lemma starfun_diff: "!!x. ( *f* f) x  - ( *f* g) x = ( *f* (%x. f x - g x)) x"
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−by (transfer, rule refl)
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−declare starfun_diff [symmetric, simp]
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−
+
−(*--------------------------------------
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−  composition: ( *f) o ( *g) = *(f o g)
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− ---------------------------------------*)
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−
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−lemma starfun_o2: "(%x. ( *f* f) (( *f* g) x)) = *f* (%x. f (g x))"
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−by (transfer, rule refl)
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−
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−lemma starfun_o: "( *f* f) o ( *f* g) = ( *f* (f o g))"
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−by (transfer o_def, rule refl)
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−
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−text{*NS extension of constant function*}
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−lemma starfun_const_fun [simp]: "!!x. ( *f* (%x. k)) x = star_of k"
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−by (transfer, rule refl)
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−
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−text{*the NS extension of the identity function*}
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−
+
−lemma starfun_Id [simp]: "!!x. ( *f* (%x. x)) x = x"
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−by (transfer, rule refl)
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−
+
−(* this is trivial, given starfun_Id *)
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−lemma starfun_Idfun_approx:
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−  "x @= star_of a ==> ( *f* (%x. x)) x @= star_of a"
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−by (simp only: starfun_Id)
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−
+
−text{*The Star-function is a (nonstandard) extension of the function*}
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−
+
−lemma is_starext_starfun: "is_starext ( *f* f) f"
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−apply (simp add: is_starext_def, auto)
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−apply (rule_tac x = x in star_cases)
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−apply (rule_tac x = y in star_cases)
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−apply (auto intro!: bexI [OF _ Rep_star_star_n]
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−            simp add: starfun star_n_eq_iff)
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−done
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−
+
−text{*Any nonstandard extension is in fact the Star-function*}
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−
+
−lemma is_starfun_starext: "is_starext F f ==> F = *f* f"
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−apply (simp add: is_starext_def)
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−apply (rule ext)
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−apply (rule_tac x = x in star_cases)
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−apply (drule_tac x = x in spec)
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−apply (drule_tac x = "( *f* f) x" in spec)
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−apply (auto simp add: starfun_star_n)
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−apply (simp add: star_n_eq_iff [symmetric])
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−apply (simp add: starfun_star_n [of f, symmetric])
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−done
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−
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−lemma is_starext_starfun_iff: "(is_starext F f) = (F = *f* f)"
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−by (blast intro: is_starfun_starext is_starext_starfun)
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−
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−text{*extented function has same solution as its standard
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−   version for real arguments. i.e they are the same
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−   for all real arguments*}
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−lemma starfun_eq: "( *f* f) (star_of a) = star_of (f a)"
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−by (rule starfun_star_of)
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−
+
−lemma starfun_approx: "( *f* f) (star_of a) @= star_of (f a)"
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−by simp
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−
+
−(* useful for NS definition of derivatives *)
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−lemma starfun_lambda_cancel:
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−  "!!x'. ( *f* (%h. f (x + h))) x'  = ( *f* f) (star_of x + x')"
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−by (transfer, rule refl)
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−
+
−lemma starfun_lambda_cancel2:
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−  "( *f* (%h. f(g(x + h)))) x' = ( *f* (f o g)) (star_of x + x')"
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−by (unfold o_def, rule starfun_lambda_cancel)
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−
+
−lemma starfun_mult_HFinite_approx:
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−  fixes l m :: "'a::real_normed_algebra star"
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−  shows "[| ( *f* f) x @= l; ( *f* g) x @= m;
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−                  l: HFinite; m: HFinite
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−               |] ==>  ( *f* (%x. f x * g x)) x @= l * m"
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−apply (drule (3) approx_mult_HFinite)
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−apply (auto intro: approx_HFinite [OF _ approx_sym])
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−done
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−
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−lemma starfun_add_approx: "[| ( *f* f) x @= l; ( *f* g) x @= m
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−               |] ==>  ( *f* (%x. f x + g x)) x @= l + m"
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−by (auto intro: approx_add)
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−
+
−text{*Examples: hrabs is nonstandard extension of rabs
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−              inverse is nonstandard extension of inverse*}
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−
+
−(* can be proved easily using theorem "starfun" and *)
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−(* properties of ultrafilter as for inverse below we  *)
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−(* use the theorem we proved above instead          *)
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−
+
−lemma starfun_rabs_hrabs: "*f* abs = abs"
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−by (simp only: star_abs_def)
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−
+
−lemma starfun_inverse_inverse [simp]: "( *f* inverse) x = inverse(x)"
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−by (simp only: star_inverse_def)
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−
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−lemma starfun_inverse: "!!x. inverse (( *f* f) x) = ( *f* (%x. inverse (f x))) x"
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−by (transfer, rule refl)
+
−declare starfun_inverse [symmetric, simp]
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−
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−lemma starfun_divide: "!!x. ( *f* f) x / ( *f* g) x = ( *f* (%x. f x / g x)) x"
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−by (transfer, rule refl)
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−declare starfun_divide [symmetric, simp]
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−
+
−lemma starfun_inverse2: "!!x. inverse (( *f* f) x) = ( *f* (%x. inverse (f x))) x"
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−by (transfer, rule refl)
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−
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−text{*General lemma/theorem needed for proofs in elementary
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−    topology of the reals*}
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−lemma starfun_mem_starset:
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−      "!!x. ( *f* f) x : *s* A ==> x : *s* {x. f x  \<in> A}"
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−by (transfer, simp)
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−
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−text{*Alternative definition for hrabs with rabs function
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−   applied entrywise to equivalence class representative.
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−   This is easily proved using starfun and ns extension thm*}
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−lemma hypreal_hrabs:
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−     "abs (star_n X) = star_n (%n. abs (X n))"
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−by (simp only: starfun_rabs_hrabs [symmetric] starfun)
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−
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−text{*nonstandard extension of set through nonstandard extension
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−   of rabs function i.e hrabs. A more general result should be
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−   where we replace rabs by some arbitrary function f and hrabs
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−   by its NS extenson. See second NS set extension below.*}
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−lemma STAR_rabs_add_minus:
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−   "*s* {x. abs (x + - y) < r} =
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−     {x. abs(x + -star_of y) < star_of r}"
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−by (transfer, rule refl)
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−
+
−lemma STAR_starfun_rabs_add_minus:
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−  "*s* {x. abs (f x + - y) < r} =
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−       {x. abs(( *f* f) x + -star_of y) < star_of r}"
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−by (transfer, rule refl)
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−
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−text{*Another characterization of Infinitesimal and one of @= relation.
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−   In this theory since @{text hypreal_hrabs} proved here. Maybe
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−   move both theorems??*}
+
−lemma Infinitesimal_FreeUltrafilterNat_iff2:
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−     "(star_n X \<in> Infinitesimal) =
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−      (\<forall>m. {n. norm(X n) < inverse(real(Suc m))}
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−                \<in>  FreeUltrafilterNat)"
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−by (simp add: Infinitesimal_hypreal_of_nat_iff star_of_def
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−     hnorm_def star_of_nat_def starfun_star_n
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−     star_n_inverse star_n_less real_of_nat_def)
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−
+
−lemma HNatInfinite_inverse_Infinitesimal [simp]:
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−     "n \<in> HNatInfinite ==> inverse (hypreal_of_hypnat n) \<in> Infinitesimal"
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−apply (cases n)
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−apply (auto simp add: of_hypnat_def starfun_star_n real_of_nat_def [symmetric] star_n_inverse real_norm_def
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−      HNatInfinite_FreeUltrafilterNat_iff
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−      Infinitesimal_FreeUltrafilterNat_iff2)
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−apply (drule_tac x="Suc m" in spec)
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−apply (erule ultra, simp)
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−done
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−
+
−lemma approx_FreeUltrafilterNat_iff: "star_n X @= star_n Y =
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−      (\<forall>r>0. {n. norm (X n - Y n) < r} : FreeUltrafilterNat)"
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−apply (subst approx_minus_iff)
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−apply (rule mem_infmal_iff [THEN subst])
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−apply (simp add: star_n_diff)
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−apply (simp add: Infinitesimal_FreeUltrafilterNat_iff)
+
−done
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−
+
−lemma approx_FreeUltrafilterNat_iff2: "star_n X @= star_n Y =
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−      (\<forall>m. {n. norm (X n - Y n) <
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−                  inverse(real(Suc m))} : FreeUltrafilterNat)"
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−apply (subst approx_minus_iff)
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−apply (rule mem_infmal_iff [THEN subst])
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−apply (simp add: star_n_diff)
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−apply (simp add: Infinitesimal_FreeUltrafilterNat_iff2)
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−done
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−
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−lemma inj_starfun: "inj starfun"
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−apply (rule inj_onI)
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−apply (rule ext, rule ccontr)
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−apply (drule_tac x = "star_n (%n. xa)" in fun_cong)
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−apply (auto simp add: starfun star_n_eq_iff)
+
−done
+
−
+
−end