(* *)
(**************************************************************************)
+include "logic/connectives.ma".
+
inductive Or (A,B:CProp) : CProp ≝
| Left : A → Or A B
| Right : B → Or A B.
interpretation "constructive quaternary and" 'and4 x y z t = (And4 x y z t).
+record Iff (A,B:CProp) : CProp ≝
+ { if: A → B;
+ fi: B → A
+ }.
+
+record Iff1 (A,B:CProp) : CProp ≝
+ { if1: A → B;
+ fi1: B → A
+ }.
+
+interpretation "logical iff" 'iff x y = (Iff x y).
+
+notation "hvbox(a break ⇔ b)" right associative with precedence 25 for @{'iff1 $a $b}.
+interpretation "logical iff type1" 'iff1 x y = (Iff1 x y).
+
inductive exT (A:Type) (P:A→CProp) : CProp ≝
ex_introT: ∀w:A. P w → exT A P.
interpretation "exT \snd" 'pi2a x = (pi2exT _ _ x).
interpretation "exT \snd" 'pi2b x y = (pi2exT _ _ x y).
+inductive exP (A:Type) (P:A→Prop) : CProp ≝
+ ex_introP: ∀w:A. P w → exP A P.
+
+interpretation "dependent pair for Prop" 'dependent_pair a b =
+ (ex_introP _ _ a b).
+
+interpretation "CProp exists for Prop" 'exists \eta.x = (exP _ x).
+
+definition pi1exP ≝ λA,P.λx:exP A P.match x with [ex_introP x _ ⇒ x].
+definition pi2exP ≝
+ λA,P.λx:exP A P.match x return λx.P (pi1exP ?? x) with [ex_introP _ p ⇒ p].
+
+interpretation "exP \fst" 'pi1 = (pi1exP _ _).
+interpretation "exP \fst" 'pi1a x = (pi1exP _ _ x).
+interpretation "exP \fst" 'pi1b x y = (pi1exP _ _ x y).
+interpretation "exP \snd" 'pi2 = (pi2exP _ _).
+interpretation "exP \snd" 'pi2a x = (pi2exP _ _ x).
+interpretation "exP \snd" 'pi2b x y = (pi2exP _ _ x y).
+
+
inductive exT23 (A:Type) (P:A→CProp) (Q:A→CProp) (R:A→A→CProp) : CProp ≝
ex_introT23: ∀w,p:A. P w → Q p → R w p → exT23 A P Q R.
inductive exT2 (A:Type) (P,Q:A→CProp) : CProp ≝
ex_introT2: ∀w:A. P w → Q w → exT2 A P Q.
-alias id "False" = "cic:/Coq/Init/Logic/False.ind#xpointer(1/1)".
definition Not : CProp → Prop ≝ λx:CProp.x → False.
interpretation "constructive not" 'not x = (Not x).