From 34b7023a76f83ffbd489e4a59bb068ef0f5e7c36 Mon Sep 17 00:00:00 2001 From: matitaweb Date: Wed, 12 Oct 2011 11:41:37 +0000 Subject: [PATCH] commit by user andrea --- weblib/tutorial/chapter2.ma | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/weblib/tutorial/chapter2.ma b/weblib/tutorial/chapter2.ma index ec3724cd8..21a0151cd 100644 --- a/weblib/tutorial/chapter2.ma +++ b/weblib/tutorial/chapter2.ma @@ -210,6 +210,11 @@ depend over arguments (such as arrays of a specified lenght, taken as a paramete These kind of types are quite unusual in traditional programming languages, and their study is one of the new frontiers of the current research on type systems. +There is nothing special in a subset type {a:A|P(a)}: it is just a record composed by +an element of a of type A and a proof of P(a). The crucial point is to have a language +reach enough to comprise proofs among its expressions. *) +axiom div2P n : nat → {N×N | True}. + -- 2.39.2