[Ur] Implementing StateMonad transformer

[Adam Chlipala]

On 12/12/2013 11:43 AM, Sergey Mironov wrote:
> By the way, a long term feature-request: if I understand correctly,
> pattern matching doesn't work with  left-hand values of '<-'.
>    

You're not the first to ask for this feature. :)  Here's the open issue:
     http://www.impredicative.com/mantis/view.php?id=48

Someone else sketched a solution, but somehow I haven't found the 
motivation to implement it.  I'd love to accept a related patch by 
someone else!

[There are elements of the Ur/Web toolset that I eventually get tired of 
improving.  So far these seem to have focused on parsing and the Emacs 
mode. :)]