+(**************************************************************************)
+(* ___ *)
+(* ||M|| *)
+(* ||A|| A project by Andrea Asperti *)
+(* ||T|| *)
+(* ||I|| Developers: *)
+(* ||T|| The HELM team. *)
+(* ||A|| http://helm.cs.unibo.it *)
+(* \ / *)
+(* \ / This file is distributed under the terms of the *)
+(* v GNU General Public License Version 2 *)
+(* *)
+(**************************************************************************)
-Inductive nat : Set \def
-| O : nat
-| S : nat \to nat.
-
-Inductive list (A:Set) : Set \def
-| nil : list A
-| cons : A \to list A \to list A.
+set "baseuri" "cic:/matita/tests/coercions/".
+include "legacy/coq.ma".
-Inductive bool: Set \def
-| true : bool
-| false : bool.
+inductive pos: Set \def
+| one : pos
+| next : pos \to pos.
+inductive nat:Set \def
+| O : nat
+| S : nat \to nat.
+inductive int: Set \def
+| positive: nat \to int
+| negative : nat \to int.
+inductive empty : Set \def .
-let rec len (A:Set)(l:list A) on l : nat \def
- match l:list with [
- nil \Rightarrow O
- | (cons e tl) \Rightarrow (S (len A tl))].
+let rec pos2nat x \def
+ match x with
+ [ one \Rightarrow (S O)
+ | (next z) \Rightarrow S (pos2nat z)].
-let rec plus (n,m:nat) : nat \def
- match n:nat with [
- O \Rightarrow m
- | (S x) \Rightarrow (S (plus x m)) ].
+definition nat2int \def \lambda x. positive x.
-let rec is_zero (n:nat) : bool \def
- match n:nat with [
- O \Rightarrow true
- | (S x) \Rightarrow false].
+coercion cic:/matita/tests/coercions/pos2nat.con.
-let rec nat_eq_dec (n,m:nat) : bool \def
- match n:nat with [
- O \Rightarrow
- match m:nat with [
- O \Rightarrow true
- | (S x) \Rightarrow false]
- | (S x) \Rightarrow
- match m:nat with [
- O \Rightarrow false
- | (S y) \Rightarrow (nat_eq_dec x y)]
- ].
+coercion cic:/matita/tests/coercions/nat2int.con.
+definition fst \def \lambda x,y:int.x.
-Coercion is_zero.
-Coercion len.
+theorem a: fst O one = fst (positive O) (next one).
+reflexivity.
+qed.
-Print Coer.
-Print Env.
+definition double:
+ \forall f:int \to int. pos \to int
+\def
+ \lambda f:int \to int. \lambda x : pos .f (nat2int x).
+
+definition double1:
+ \forall f:int \to int. pos \to int
+\def
+ \lambda f:int \to int. \lambda x : pos .f (pos2nat x).
+definition double2:
+ \forall f:int \to int. pos \to int
+\def
+ \lambda f:int \to int. \lambda x : pos .f (nat2int (pos2nat x)).
+
+