Theory Quotient_Sum

theory Quotient_Sum
imports Quotient_Syntax
(*  Title:      HOL/Library/Quotient_Sum.thy
Author: Cezary Kaliszyk and Christian Urban
*)


header {* Quotient infrastructure for the sum type *}

theory Quotient_Sum
imports Main Quotient_Syntax
begin

subsection {* Rules for the Quotient package *}

lemma sum_rel_map1:
"sum_rel R1 R2 (sum_map f1 f2 x) y <-> sum_rel (λx. R1 (f1 x)) (λx. R2 (f2 x)) x y"
by (simp add: sum_rel_def split: sum.split)

lemma sum_rel_map2:
"sum_rel R1 R2 x (sum_map f1 f2 y) <-> sum_rel (λx y. R1 x (f1 y)) (λx y. R2 x (f2 y)) x y"
by (simp add: sum_rel_def split: sum.split)

lemma sum_map_id [id_simps]:
"sum_map id id = id"
by (simp add: id_def sum_map.identity fun_eq_iff)

lemma sum_rel_eq [id_simps]:
"sum_rel (op =) (op =) = (op =)"
by (simp add: sum_rel_def fun_eq_iff split: sum.split)

lemma sum_symp:
"symp R1 ==> symp R2 ==> symp (sum_rel R1 R2)"
unfolding symp_def split_sum_all sum_rel_simps by fast

lemma sum_transp:
"transp R1 ==> transp R2 ==> transp (sum_rel R1 R2)"
unfolding transp_def split_sum_all sum_rel_simps by fast

lemma sum_equivp [quot_equiv]:
"equivp R1 ==> equivp R2 ==> equivp (sum_rel R1 R2)"
by (blast intro: equivpI reflp_sum_rel sum_symp sum_transp elim: equivpE)

lemma sum_quotient [quot_thm]:
assumes q1: "Quotient3 R1 Abs1 Rep1"
assumes q2: "Quotient3 R2 Abs2 Rep2"
shows "Quotient3 (sum_rel R1 R2) (sum_map Abs1 Abs2) (sum_map Rep1 Rep2)"
apply (rule Quotient3I)
apply (simp_all add: sum_map.compositionality comp_def sum_map.identity sum_rel_eq sum_rel_map1 sum_rel_map2
Quotient3_abs_rep [OF q1] Quotient3_rel_rep [OF q1] Quotient3_abs_rep [OF q2] Quotient3_rel_rep [OF q2])
using Quotient3_rel [OF q1] Quotient3_rel [OF q2]
apply (simp add: sum_rel_def comp_def split: sum.split)
done

declare [[mapQ3 sum = (sum_rel, sum_quotient)]]

lemma sum_Inl_rsp [quot_respect]:
assumes q1: "Quotient3 R1 Abs1 Rep1"
assumes q2: "Quotient3 R2 Abs2 Rep2"
shows "(R1 ===> sum_rel R1 R2) Inl Inl"
by auto

lemma sum_Inr_rsp [quot_respect]:
assumes q1: "Quotient3 R1 Abs1 Rep1"
assumes q2: "Quotient3 R2 Abs2 Rep2"
shows "(R2 ===> sum_rel R1 R2) Inr Inr"
by auto

lemma sum_Inl_prs [quot_preserve]:
assumes q1: "Quotient3 R1 Abs1 Rep1"
assumes q2: "Quotient3 R2 Abs2 Rep2"
shows "(Rep1 ---> sum_map Abs1 Abs2) Inl = Inl"
apply(simp add: fun_eq_iff)
apply(simp add: Quotient3_abs_rep[OF q1])
done

lemma sum_Inr_prs [quot_preserve]:
assumes q1: "Quotient3 R1 Abs1 Rep1"
assumes q2: "Quotient3 R2 Abs2 Rep2"
shows "(Rep2 ---> sum_map Abs1 Abs2) Inr = Inr"
apply(simp add: fun_eq_iff)
apply(simp add: Quotient3_abs_rep[OF q2])
done

end