Hi, I discovered implicit parameters today and I'm very excited about them because they allow to express certain code constructs more elegantly. However, I stumbled upon a problem. Suppose I have these definitions (the definition of Request is irrelevant): type Controller = (?req :: Request) => String controller1 :: Controller controller2 :: Controller controllerList = [controller1, controller2] GHC complains with: Unbound implicit parameter (?req :: Request) arising from use of `controller1' In the list element: controller1 In the definition of `controllerList': controllerList = [controller1, controller2] I can see why this isn't allowed; controllerList requires an implicit parameter ?req because it references functions needing this parameter. But I want it to be parameterless - it's just a static list of controller functions after all. The actual request shouldn't be supplied when selecting a controller from the list, but rather later, when invoking it. A solution is to make the parameter explicit by binding it: controllerList = [\req -> let ?req = req in controller1, \req -> let ?req = req in controller2] This works, but can't really be called elegant (the binding has to be repeated for every controller). So I tried to at least move the rebinding into a function: explicitRequest controller req = let ?req = req in controller controllerList = [explicitRequest controller1, explicitRequest controller2] This, however, is rejected by GHC. GHC doesn't seem to infer that explicitRequest hides the implicit parameter required by the controllers. Am I confused here or is this a bug in GHC? Thanks in advance, -Stefan -- [ADV] http://superversion.sf.net [/ADV]