[Ur] interfacing with C or other languages - example system

[Marc Weber]

Excerpts from Adam Chlipala's message of Tue Nov 30 00:37:53 +0100 2010:
> Couldn't you just as easily write a C function that takes "options" as 
> input and then always executes "verify-pay-confirm" with those options?  
> That would make sure the Ur/Web layer can't introduce zany 
> non-transactional behavior.

In the end you're right. The way to go is create bindings for curl and
cache the replies. If restart happens the cached reply will be
returned. Issue solved.

Does a transaction always last form the begin of generating a result
page until the end?

Thus could I use the commit callback to remove the cache ?

Could I use the context pointer as key to find a cached reply within one
attempt to generate the output page which may be retried?
Thus will the same ctx be passed when a request is rerun?
Or is there no way to limit caching to a HTTP request only?

Marc Weber