On Sat, Apr 14, 2012 at 7:38 PM, Petar Radosevic wrote:

Hi,

I would love to create a port of Webmachine [1] in Haskell so I can learn the language and in the meanwhile create something useful. The problem is, I don't know how I would design such a system in Haskell.

Simply put, webmachine is a library in Erlang which let's you create a REST API by binding resources to URI's. The resources have sane defaults, defined with functions, like `resource_exists`, `service_available` and `is_authorized`. You can override these functions per resource to create your own API. Webmachine will then create the appropriate response when a request comes in.

I have been thinking how to implement such a system in Haskell, and I have come up with the following. First of, use WAI with Warp to handle the `Request` -> `Response` cycle. That was easy to come up with, but I'm still struggling with the following question: What would a `Resource` be in Haskell? I need something that lets me define sane defaults which I can override per resource. Should I have a `Resource` typeclass which defines all the default functions? Or is there a better way to accomplish this?

I hope the above was a bit clear, would appreciate any insights!

[1]: http://wiki.basho.com/Webmachine-Resource.html -- Petar Radosevic | @wunki

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Hi Petar, When I was at QCon, I heard a talk from Steve Vinoski on Webmachine, and I was surprised to hear how close webmachine was to Haskell already, The concept is basically sticking a state monad on top of WAI. My guess is you would want to use a record type for a Resource, not a typeclass, to make it easier to swap out behaviors. But honestly, I haven't given this any thought since I saw the presentation 6 months ago. Michael