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
My brief answer is: OO is not powerful enough to replace type classes. The most straightforward translation is to pass a dictionary of operations, as in one typical typeclass implementation. That is if typeclass Foo defines three methods, then define a class/record type named Foo, and then change functions of Foo a => yadda -> … Read more
Dr Jon Harrop, whom I contacted over e-mail, explained what is going on: The problem is simply that the program has been optimized for Python. This is common when the programmer is more familiar with one language than the other, of course. You just have to learn a different set of rules that dictate how … 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
This should work: typedefof<System.IEnumerable<_>> EDIT As Tomas notes, there’s nothing special about the _ wildcard here; F# infers that the type obj is the most general applicable type in this context, so this is the same as using typedefof<System.IEnumerable<obj>>. In some cases the way this works can be a bit of a hindrance, though. For … Read more
C# compiler does not give you any guarantees about tail-call optimizations because C# programs usually use loops and so they do not rely on the tail-call optimizations. So, in C#, this is simply a JIT optimization that may or may not happen (and you cannot rely on it). F# compiler is designed to handle functional … 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