<br><div class="gmail_quote">On Thu, Feb 4, 2010 at 10:03 PM, Chris Casinghino <span dir="ltr"><<a href="mailto:chris.casinghino@gmail.com">chris.casinghino@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Hi all,<br>
<br>
I triggered the error in the subject line by trying to define a<br>
datatype whose Sort depended on one of its indices. I'm curious about<br>
this restriction: is there a theoretic reason for it or was it just a<br>
matter of convenience in the implementation.<br></blockquote><div><br></div><div>Both, I would say. I have no idea what the theory for such a datatype would</div><div>be, and it would mean more work when checking levels of datatypes.</div>
<div><br></div><div>At the moment to check the level of a datatype we check that all the constructor</div><div>arguments have types that fit inside the target level of the datatype. With</div><div>your datatype this level might be different for each constructor and it depends</div>
<div>on the values of the constructor arguments.</div><div><br></div><div>/ Ulf</div></div>