From 57d183c7955fb54b3eb6dd431f5aec338131266b Mon Sep 17 00:00:00 2001
From: Josh Chen
Date: Fri, 22 Feb 2019 23:45:50 +0100
Subject: Cleanups and reorganization

---
 More_Types.thy | 83 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)
 create mode 100644 More_Types.thy

(limited to 'More_Types.thy')

diff --git a/More_Types.thy b/More_Types.thy
new file mode 100644
index 0000000..9125aca
--- /dev/null
+++ b/More_Types.thy
@@ -0,0 +1,83 @@
+(********
+Isabelle/HoTT: Coproduct, unit, and empty types
+Feb 2019
+
+********)
+
+theory More_Types
+imports HoTT_Base
+
+begin
+
+
+section \<open>Coproduct type\<close>
+
+axiomatization
+  Cprd    :: "[t, t] \<Rightarrow> t"  (infixr "+" 50) and
+  inl     :: "[t, t, t] \<Rightarrow> t" and
+  inr     :: "[t, t, t] \<Rightarrow> t" and
+  indCprd :: "[t \<Rightarrow> t, t \<Rightarrow> t, t \<Rightarrow> t, t] \<Rightarrow> t"
+where
+  Cprd_form: "\<lbrakk>A: U i; B: U i\<rbrakk> \<Longrightarrow> A + B: U i" and
+
+  Cprd_intro_inl: "\<lbrakk>a: A; B: U i\<rbrakk> \<Longrightarrow> inl A B a: A + B" and
+
+  Cprd_intro_inr: "\<lbrakk>b: B; A: U i\<rbrakk> \<Longrightarrow> inr A B b: A + B" and
+
+  Cprd_elim: "\<lbrakk>
+    u: A + B;
+    C: A + B \<leadsto> U i;
+    \<And>x. x: A \<Longrightarrow> c x: C (inl A B x);
+    \<And>y. y: B \<Longrightarrow> d y: C (inr A B y) \<rbrakk> \<Longrightarrow> indCprd C c d u: C u" and
+
+  Cprd_cmp_inl: "\<lbrakk>
+    a: A;
+    C: A + B \<leadsto> U i;
+    \<And>x. x: A \<Longrightarrow> c x: C (inl A B x);
+    \<And>y. y: B \<Longrightarrow> d y: C (inr A B y) \<rbrakk> \<Longrightarrow> indCprd C c d (inl A B a) \<equiv> c a" and
+
+  Cprd_cmp_inr: "\<lbrakk>
+    b: B;
+    C: A + B \<leadsto> U i;
+    \<And>x. x: A \<Longrightarrow> c x: C (inl A B x);
+    \<And>y. y: B \<Longrightarrow> d y: C (inr A B y) \<rbrakk> \<Longrightarrow> indCprd C c d (inr A B b) \<equiv> d b"
+
+lemmas Cprd_form [form]
+lemmas Cprd_routine [intro] = Cprd_form Cprd_intro_inl Cprd_intro_inr Cprd_elim
+lemmas Cprd_comp [comp] = Cprd_cmp_inl Cprd_cmp_inr
+
+
+section \<open>Unit type\<close>
+
+axiomatization
+  Unit    :: t and
+  pt      :: t and
+  indUnit :: "[t \<Rightarrow> t, t, t] \<Rightarrow> t"
+where
+  Unit_form: "Unit: U O" and
+
+  Unit_intro: "pt: Unit" and
+
+  Unit_elim: "\<lbrakk>x: Unit; c: C pt; C: Unit \<leadsto> U i\<rbrakk> \<Longrightarrow> indUnit C c x: C x" and
+
+  Unit_cmp: "\<lbrakk>c: C Unit; C: Unit \<leadsto> U i\<rbrakk> \<Longrightarrow> indUnit C c pt \<equiv> c"
+
+lemmas Unit_form [form]
+lemmas Unit_routine [intro] = Unit_form Unit_intro Unit_elim
+lemmas Unit_cmp [comp]
+
+
+section \<open>Empty type\<close>
+
+axiomatization
+  Null    :: t and
+  indNull :: "[t \<Rightarrow> t, t] \<Rightarrow> t"
+where
+  Null_form: "Null: U O" and
+
+  Null_elim: "\<lbrakk>z: Null; C: Null \<leadsto> U i\<rbrakk> \<Longrightarrow> indNull C z: C z"
+
+lemmas Null_form [form]
+lemmas Null_routine [intro] = Null_form Null_elim
+
+end
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