Thanks Brandon, forgot to send my reply to the list: Ok, so I am confusing things. Good to know. So my question is how do I fulfill this scenario? - I have an action that might return either an HttpResponse or an HttpRequest, depending on if the IO in the action determined more work needed doing. It's here, though I doubt it's "correct" yet: requestHandler :: HttpRequest -> IO HttpResponse requestHandler request = do session <- sessionHandler request ret <- uriHandler request case ret of HttpResponse -> ret HttpRequest -> resourceHandler session ret uriHandler :: HttpRequest -> IO HttpMessage sessionHandler :: HttpRequest -> IO HttpSession I've given the uriHandler a signature of IO HttpMessage because the HttpMessage might be either an HttpResponse or an HttpRequest, and I don't know how I should be specifying that. Ideas? - Stephen Brandon S. Allbery KF8NH wrote:
On Jun 18, 2008, at 15:31 , Stephen Howard wrote:
HttpMessage.hs:36:20: Not in scope: type constructor or class `HttpRequest'
The troublesome line is the definition of the cookie function at the end of the code. I've made
Right. "HttpRequest" is a data constructor associated with the type constructor "HttpMessage". (Data constructors are effectively functions; you used it in the context of a type, not a function name.)