From: Nicolai Kraus <nicolai.kraus@gmail.com>
To: Jean Joseph <jsjean00@gmail.com>,
Homotopy Type Theory <HomotopyTypeTheory@googlegroups.com>
Subject: Re: [HoTT] Propositional Truncation
Date: Tue, 5 Mar 2019 22:47:51 +0000 [thread overview]
Message-ID: <fcb9a985-f144-aaea-36a9-3e4c65829b32@gmail.com> (raw)
In-Reply-To: <0f5b8d0e-9f1d-47a7-9d39-a9112afb77ea@googlegroups.com>
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You can't have a function which, for all A, gives you ||A|| -> A. See
the exercises 3.11 and 3.12!
-- Nicolai
On 05/03/19 22:31, Jean Joseph wrote:
> Hi,
>
> From the HoTT book, the truncation of any type A has two constructors:
>
> 1) for any a : A, there is |a| : ||A||
> 2) for any x,y : ||A||, x = y.
>
> I get that if A is inhabited, then ||A|| is inhabited by (1). But is
> it true that, if ||A|| is inhabited, then A is inhabited?
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next prev parent reply other threads:[~2019-03-05 22:47 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-05 22:31 Jean Joseph
2019-03-05 22:47 ` Nicolai Kraus [this message]
2019-03-05 23:07 ` Martín Hötzel Escardó
2019-03-07 14:10 ` Licata, Dan
2019-03-07 16:16 ` Martín Hötzel Escardó
2019-03-07 16:35 ` Ben Sherman
2019-03-07 21:52 ` Anders Mörtberg
2019-03-07 22:41 ` Martín Hötzel Escardó
2019-03-07 22:51 ` Licata, Dan
2019-03-07 23:01 ` Martín Hötzel Escardó
2019-03-07 23:23 ` Martín Hötzel Escardó
2019-03-08 14:59 ` Anders Mortberg
2019-03-08 15:13 ` Licata, Dan
2019-03-08 22:28 ` Martín Hötzel Escardó
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