<br><br><div class="gmail_quote">On Wed, Aug 22, 2012 at 9:40 AM, Nils Anders Danielsson <span dir="ltr"><<a href="mailto:nad@chalmers.se" target="_blank">nad@chalmers.se</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="im">On 2012-08-21 23:09, Andrés Sicard-Ramírez wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Yes, the type _≡_ can also be defined in Coq, but I don't see its<br>
relation to the head type constraints (as described in the Coq'Art).<br>
</blockquote>
<br></div>
I don't know what constraints you are referring to.</blockquote><div><br>From Coq'Art, p. 379:<br><br>The type of constructors of an inductive type T has the following form:<br><br>t₁ → t₂ → ... t_l → T a₁ ... a_k.<br>
<br>The type T cannot appear among the arguments a₁ ... a_k. For<br>example, the following definition is rejected<br><br>Inductive T : Set → Set := c : T (T nat).<br>Error: Non strictly positive occurrence of "T" in "T (T nat)"<br clear="all">
</div></div><br>-- <br>Andrés<br><br>