(* Title: HOL/Sum_Type.thy ID: $Id$ Author: Lawrence C Paulson, Cambridge University Computer Laboratory Copyright 1992 University of Cambridge *) header{*The Disjoint Sum of Two Types*} theory Sum_Type imports Product_Type begin text{*The representations of the two injections*} constdefs Inl_Rep :: "['a, 'a, 'b, bool] => bool" "Inl_Rep == (%a. %x y p. x=a & p)" Inr_Rep :: "['b, 'a, 'b, bool] => bool" "Inr_Rep == (%b. %x y p. y=b & ~p)" global typedef (Sum) ('a, 'b) "+" (infixr 10) = "{f. (? a. f = Inl_Rep(a::'a)) | (? b. f = Inr_Rep(b::'b))}" by auto local text{*abstract constants and syntax*} constdefs Inl :: "'a => 'a + 'b" "Inl == (%a. Abs_Sum(Inl_Rep(a)))" Inr :: "'b => 'a + 'b" "Inr == (%b. Abs_Sum(Inr_Rep(b)))" Plus :: "['a set, 'b set] => ('a + 'b) set" (infixr "<+>" 65) "A <+> B == (Inl`A) Un (Inr`B)" --{*disjoint sum for sets; the operator + is overloaded with wrong type!*} Part :: "['a set, 'b => 'a] => 'a set" "Part A h == A Int {x. ? z. x = h(z)}" --{*for selecting out the components of a mutually recursive definition*} (** Inl_Rep and Inr_Rep: Representations of the constructors **) (*This counts as a non-emptiness result for admitting 'a+'b as a type*) lemma Inl_RepI: "Inl_Rep(a) : Sum" by (auto simp add: Sum_def) lemma Inr_RepI: "Inr_Rep(b) : Sum" by (auto simp add: Sum_def) lemma inj_on_Abs_Sum: "inj_on Abs_Sum Sum" apply (rule inj_on_inverseI) apply (erule Abs_Sum_inverse) done subsection{*Freeness Properties for @{term Inl} and @{term Inr}*} text{*Distinctness*} lemma Inl_Rep_not_Inr_Rep: "Inl_Rep(a) ~= Inr_Rep(b)" by (auto simp add: Inl_Rep_def Inr_Rep_def expand_fun_eq) lemma Inl_not_Inr [iff]: "Inl(a) ~= Inr(b)" apply (simp add: Inl_def Inr_def) apply (rule inj_on_Abs_Sum [THEN inj_on_contraD]) apply (rule Inl_Rep_not_Inr_Rep) apply (rule Inl_RepI) apply (rule Inr_RepI) done lemmas Inr_not_Inl = Inl_not_Inr [THEN not_sym, standard, iff] lemmas Inl_neq_Inr = Inl_not_Inr [THEN notE, standard] lemmas Inr_neq_Inl = sym [THEN Inl_neq_Inr, standard] text{*Injectiveness*} lemma Inl_Rep_inject: "Inl_Rep(a) = Inl_Rep(c) ==> a=c" by (auto simp add: Inl_Rep_def expand_fun_eq) lemma Inr_Rep_inject: "Inr_Rep(b) = Inr_Rep(d) ==> b=d" by (auto simp add: Inr_Rep_def expand_fun_eq) lemma inj_Inl: "inj(Inl)" apply (simp add: Inl_def) apply (rule inj_onI) apply (erule inj_on_Abs_Sum [THEN inj_onD, THEN Inl_Rep_inject]) apply (rule Inl_RepI) apply (rule Inl_RepI) done lemmas Inl_inject = inj_Inl [THEN injD, standard] lemma inj_Inr: "inj(Inr)" apply (simp add: Inr_def) apply (rule inj_onI) apply (erule inj_on_Abs_Sum [THEN inj_onD, THEN Inr_Rep_inject]) apply (rule Inr_RepI) apply (rule Inr_RepI) done lemmas Inr_inject = inj_Inr [THEN injD, standard] lemma Inl_eq [iff]: "(Inl(x)=Inl(y)) = (x=y)" by (blast dest!: Inl_inject) lemma Inr_eq [iff]: "(Inr(x)=Inr(y)) = (x=y)" by (blast dest!: Inr_inject) subsection{*The Disjoint Sum of Sets*} (** Introduction rules for the injections **) lemma InlI [intro!]: "a : A ==> Inl(a) : A <+> B" by (simp add: Plus_def) lemma InrI [intro!]: "b : B ==> Inr(b) : A <+> B" by (simp add: Plus_def) (** Elimination rules **) lemma PlusE [elim!]: "[| u: A <+> B; !!x. [| x:A; u=Inl(x) |] ==> P; !!y. [| y:B; u=Inr(y) |] ==> P |] ==> P" by (auto simp add: Plus_def) text{*Exhaustion rule for sums, a degenerate form of induction*} lemma sumE: "[| !!x::'a. s = Inl(x) ==> P; !!y::'b. s = Inr(y) ==> P |] ==> P" apply (rule Abs_Sum_cases [of s]) apply (auto simp add: Sum_def Inl_def Inr_def) done lemma sum_induct: "[| !!x. P (Inl x); !!x. P (Inr x) |] ==> P x" by (rule sumE [of x], auto) subsection{*The @{term Part} Primitive*} lemma Part_eqI [intro]: "[| a : A; a=h(b) |] ==> a : Part A h" by (auto simp add: Part_def) lemmas PartI = Part_eqI [OF _ refl, standard] lemma PartE [elim!]: "[| a : Part A h; !!z. [| a : A; a=h(z) |] ==> P |] ==> P" by (auto simp add: Part_def) lemma Part_subset: "Part A h <= A" by (auto simp add: Part_def) lemma Part_mono: "A<=B ==> Part A h <= Part B h" by blast lemmas basic_monos = basic_monos Part_mono lemma PartD1: "a : Part A h ==> a : A" by (simp add: Part_def) lemma Part_id: "Part A (%x. x) = A" by blast lemma Part_Int: "Part (A Int B) h = (Part A h) Int (Part B h)" by blast lemma Part_Collect: "Part (A Int {x. P x}) h = (Part A h) Int {x. P x}" by blast ML {* val Inl_RepI = thm "Inl_RepI"; val Inr_RepI = thm "Inr_RepI"; val inj_on_Abs_Sum = thm "inj_on_Abs_Sum"; val Inl_Rep_not_Inr_Rep = thm "Inl_Rep_not_Inr_Rep"; val Inl_not_Inr = thm "Inl_not_Inr"; val Inr_not_Inl = thm "Inr_not_Inl"; val Inl_neq_Inr = thm "Inl_neq_Inr"; val Inr_neq_Inl = thm "Inr_neq_Inl"; val Inl_Rep_inject = thm "Inl_Rep_inject"; val Inr_Rep_inject = thm "Inr_Rep_inject"; val inj_Inl = thm "inj_Inl"; val Inl_inject = thm "Inl_inject"; val inj_Inr = thm "inj_Inr"; val Inr_inject = thm "Inr_inject"; val Inl_eq = thm "Inl_eq"; val Inr_eq = thm "Inr_eq"; val InlI = thm "InlI"; val InrI = thm "InrI"; val PlusE = thm "PlusE"; val sumE = thm "sumE"; val sum_induct = thm "sum_induct"; val Part_eqI = thm "Part_eqI"; val PartI = thm "PartI"; val PartE = thm "PartE"; val Part_subset = thm "Part_subset"; val Part_mono = thm "Part_mono"; val PartD1 = thm "PartD1"; val Part_id = thm "Part_id"; val Part_Int = thm "Part_Int"; val Part_Collect = thm "Part_Collect"; val basic_monos = thms "basic_monos"; *} end