I also think it would be really good to have some documentation that explains the type system and how to do neat things with it in terms that a reasonably competent haskell / ML programmer could understand. 

I played around with Ur/Web about a year ago and was able to make a simple application, and use some C libraries (the C FFI is really easy to use), but realized that I wasn't able to do much of anything beyond mimicking the demos in various ways, mainly because the documentation was so sparse (when I didn't know how to do something, I just tried to do what I would expect it to do if it were haskell, which worked a surprising amount of the time, but wasn't the most enjoyable experience).

Looking at, for example, page 19 of the reference manual [1], which is supposed to explain how expressions are typed (which I would assume would give input into how the type system worked), I, probably like Chris, couldn't make much sense of it. Now I don't have a PhD in type theory, or even a masters degree, but if your intended audience includes people like me, the documentation definitely needs work! 

Now perhaps understanding those tables isn't actually important to using the language, but from looking through the manual / available documentation, there seems to be the really basic cookbook style stuff, that you can copy and paste and modify, as long as you are careful, then the source code itself, from which more can be gleaned, and then this type of type theory. Because of this (or until there is real documentation explaining some of the novel things about this language), I think Ur/Web is going to remain a cool thing that barely anyone can do anything with. Something to be linked in reddit or stack overflow posts, but not actually used! It seems like documentation of the really basic stuff is there, and the really advanced stuff (which is great, don't get me wrong), but the stuff in the middle is missing! Which is too bad, because it seems like it is doing some really exciting things.

1. http://www.impredicative.com/ur/manual.pdf

On Jul 13, 2011, at 11:10 AM, Christopher Done wrote:

On 13 July 2011 15:28, Adam Chlipala <adamc@impredicative.com> wrote:
I write to mention briefly that I'm looking for people interested in writing
Ur/Web programs for pay.  Ur/Web is a DSL for building modern web
applications, and I believe it is truly a secret weapon for that domain, and
one that should appeal to many Haskell fans.  I have one customer now for
whom I'm leading a project to develop a particular web application, and I'd
like to have more.  The current project would benefit from more programming
help, and I would also like to develop a network of people interested in
future projects.

More information on Ur/Web can be found here:
   http://www.impredicative.com/ur/

I would like to see a real application in Ur/Web. There are many
simple examples. I don't and wouldn't want to develop like that,
writing raw HTML and SQL seems going backwards despite the incredible
advances in consistency and correctness that Ur/Web offers. I also
find it hard to understand the type system in a non-superficial level
because the related paper was very hard to grok. I tried to get it
running a while ago and could not get it to compile. I would also like
to see how it handles non-web stuff as inevitably IME web applications
involve more than merely reading and writing to a database.

I like the idea, please keep us posted about it.

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