[Agda] Highest Level seen?
Darryl
psygnisfive at yahoo.com
Tue Dec 25 07:28:46 CET 2012
I've wondered on numerous occasions whether or not pure sets (ie no data declarations) gives a traditional iterated conception of set. I've never fully determined if the answer is yes or no. I think you might need Lift as the only data decl to get that, maybe? But the absence of pattern matching on types makes it useless.
- darryl
________________________________
From: Jacques Carette <carette at mcmaster.ca>
To: Darryl <psygnisfive at yahoo.com>
Cc: Agda <Agda at lists.chalmers.se>
Sent: Monday, December 24, 2012 8:39 AM
Subject: Re: [Agda] Highest Level seen?
I would be quite surprised if it were so. I was more going for a rough analogy.
What I do find I am missing is a nice way to tell Agda that I want
certain inhabitants of Set0 to be 'small'. To be more precise, I
sometimes want a Setoid S whose carrier set C : Set is such that I
have a function interp : C -> Set. Basically I want to
interpret C as a set-of-sets in Set. Another way to see it is
that C is formed from those sets whose power-set is
representable. As far as I can tell, in such a situation C really
ought to be in Set_{-1}, and assuming we have a 'small' equality
as well, then Setoid S would be in Set0, not Set1. In the codes I
have, this would definitely help keep universe sizes way down.
Jacques
On 12-12-23 11:25 PM, Darryl wrote:
Is it strictly true that sets, classes, and conglomerates are equivalent to Set0, Set1, and Set2, respectively?
>
>- darryl
>
>
>________________________________
> From: Jacques Carette <carette at mcmaster.ca>
>To: Agda <Agda at lists.chalmers.se>
>Sent: Saturday, December 22, 2012 11:11 AM
>Subject: [Agda] Highest Level seen?
>
>I am curious about one point: what is the highest Level that
has been seen in practice in an Agda development? [Of
course, one can artificially go arbitrarily high; by 'in
practice', I mean in the course of developing some theory
for the purposes of applications]
>
>A lot of Agda is done in a level-polymorphic way. What I
mean by my question is then: how many suc's did you have to
put in to make things go through?
>
>In standard mathematics, when people worry about size, they
tend to go with sets, classes, and super-classes (sometimes
called conglomerates), and no higher. This would seem to
indicate that, 'in the wild', Set_2 is all that is really
needed. Of course, given the sloppiness of standard
mathematics, one wonders if what they do really does
level-check...
>
>Jacques
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