A few things. First, the difference between let resp = req.GetResponse() and let! resp = req.AsyncGetReponse() is that for the probably hundreds of milliseconds (an eternity to the CPU) where the web request is ‘at sea’, the former is using one thread (blocked on I/O), whereas the latter is using zero threads. This is the … Read more
I needed version 4.0.0 of FSharp.Core, so I installed it in my Visual Studio 2010 via Nuget: http://nuget.org/packages/FSharp.Core Or run the following command in the Package Manager Console: PM> Install-Package FSharp.Core Then publish the project and upload FSharp.Core.dll
For me, installing the Microsoft.Bcl.AsyncInterfaces (Nuget package) fixed the issue.
The protected modifier can be quite problematic in F#, because you often need to call members from a lambda expression. However, when you do that, you no longer access the method from within the class. This also causes confusion when using protected members declared in C# (see for example this SO question). If you could … Read more
Some is not a keyword. There is an option type however, which is a discriminated union containing two things: Some which holds a value of some type. None which represents lack of value. It’s defined as: type ‘a option = | None | Some of ‘a It acts kind of like a nullable type, where … Read more
Yes, F# has it’s own reflection layer build on top of .NET’s reflection to help you make sense of types that are specific to F#, like discriminating unions. Here’s the code that will let you enumerate a union’s cases: open Microsoft.FSharp.Reflection type MyDU = | One | Two | Three let cases = FSharpType.GetUnionCases typeof<MyDU> … Read more
Start with a simple task, like mapping items from ‘a to ‘b in a list. We want to write a function which has the signature val map: (‘a -> ‘b) -> ‘a list -> ‘b list Where map (fun x -> x * 2) [1;2;3;4;5] == [2;4;6;8;10] Start with non-tail recursive version: let rec map … Read more
To elaborate a bit on collection initialization in F#, here are a few examples: read-only dictionary dict [ (1, “a”); (2, “b”); (3, “c”) ] seq (IEnumerable<T>) seq { 0 .. 99 } list [1; 2; 3; 4; 5] set set [1; 2; 3; 4; 5] array [| 1; 2; 3; 4; 5 |]
Quick answer: No, that’s beyond the capabilities of current OCaml type inference. To explain it a bit more: type inference in most functional languages is based on a concept called unification, which is really just a specific way of solving equations. For example, inferring the type of an expression like let f l i j … Read more
The semantics for this is the same as in F# (probably because F# is based on OCaml): function allows the use of pattern matching (i.e. |), but consequently it can be passed only one argument. function p_1 -> exp_1 | … | p_n -> exp_n is equivalent to fun exp -> match exp with p_1 … Read more