[Update: This blog post was orignally posted in early 2008, in another blog. Things have changed a little in F#, and Ted Nedward has provided updated information related to this, showing how to create data contracts in F#] On the road to a really interesting Web Service, I increased the complexity of my "could-not-be-simpler" web service one notch, and added a class-typed argument to the operation. This requires constructing of a Data Contract, so that WCF can build the correct WSDL, and also know...

I had half an hour to fill while I waited for a large download, on my slow connection. I'd thought about re-implementing my C# WCF test host in F#. It didn't look too complex, and indeed it wasn't: #light #I @"C:\Program Files\Reference Assemblies\Microsoft\Framew... #r "System.ServiceModel.dll" #r "Server.dll" open System open System.ServiceModel open System.Diagnostics open Coyote.FSWCFTest let services = [ (typeof<TestWebService>, "http://localhost:8080/Test... ] let...

I tidied up the F# web service, mainly by factoring out an interface for the web service. Without the attributes it looks like this: type ITestWebService = abstract TestMethod: Param:string -> string type TestWebService() = interface ITestWebService with member x.TestMethod s = "Hello " + s; However, I noticed when I was setting up the C# host, I needed to cast to get to access the interface, like this: TestWebService tws = new TestWebService(); ITestWebService itws = tws as ITestWebService; Neither...

For all the power and flexibility that WCF provides, creating a basic web service in C# is easy enough. Essentially, it's just a POCO adorned with some special attributes. Doing the same thing in F#, then, should also be easy enough. I tried this: #light #I @"C:\Program Files\Reference Assemblies\Microsoft\Framew... #r "System.ServiceModel.dll" open System.ServiceModel [<ServiceContract(Config... = "TestWebService", Namespace = "http://coyote-software.com... [<ServiceBehavior(Instan...

All this currying and partial application stuff is all very interesting, but surely its has to have some kind of run-time performance hit. What if I just want to keep things straightforward? Firstly, if we have a function that takes only a single argument, there is nothing to curry. It makes no sense to call a function with no arguments, so your only option is to make the exact call. That in mind, we can do this: let repeat(str, n) = ... That syntax is sure to catch out C# programmers (like me),...

In my last two posts, I described how F# transforms functions with more than one argument into chains of functions with a single argument. Strictly speaking, all functions in F# must have exactly one argument, and return exactly one result. There is a special type, unit, which can be used as a dummy when no argument or return is required, like void in C#. F#’s functions are lambda functions, formally described by lambda calculus which provides the theoretic model for functional languages. Happily,...

OK, so you define a function that takes 2 parameters, but you actually get a function that takes 1 parameter, and returns a function that will take the second parameter and return the final result. Hmm, this raises lots of questions. What happens if the function has more than two parameters? >let f a b c = a + b + c is of type val f : int -> int -> int -> int So we get a chain of functions, each one taking exactly one parameter, and returning a function that takes the next. If there are...

I’ve been spending some time recently looking at F# - I have a specific task in mind to which F# seems very well suited, so the motivation is there! After many years doing C then C++ and now C#, it’s easy to fall into the trap of thinking some things work just the same in F#. One example of this is functions. I was happily experimenting with some code, thinking I was getting the measure of F#, but one small detail kept catching my eye - the very strange types reported for functions. It all starts...