String.Join is a .NET method. When using a .NET method, F# views it as a function that takes a tuple as an argument (when calling it you write parameters as f(a, b)). The |> operator can be used with functions that use the curried form of parameters (and can be called by writing f a … Read more
An important point that hasn’t been mentioned so far is the difference between if .. then .. else and if .. then without the else branch. If in functional languages The functional interpretation of if is that it is an expression that evaluates to some value. To evaluate the value of if c then e1 … Read more
The answer from @meziantou already gives a nice overview of the options (and how they behave differently), so let me just give a brief summary, or list of recommendations: Use let or let mutable if you want to define a local value that is visible only within the type (essentially a private field or a … Read more
.fsx is for individual files intended to run as a script. In particular, in an .fsx file you can use things like #r “Foo.dll” to dynamically load a library and #load “Foo.fsx” to load another script file. [Edit: and starting with .NET 5, #r “nuget: FooBar” to load a NuGet package.] .fs is for source … Read more
Executive summary: I wrote a simple implementation of an algorithm… that wasn’t tail-recursive. I compiled it with OCaml under Linux. It worked fine, and finished in 0.14 seconds. It was then time to port to F#. I translated the code (direct translation) to F#. I compiled under Windows, and run it – I got a … Read more
If you’re using .NET 4.0, you can just use File.ReadLines. > let readLines filePath = System.IO.File.ReadLines(filePath);; val readLines : string -> seq<string>
(**) and pown are two different things. When you see (**), you can think of the mathematical formula using logarithms. When you see pown, it’s just a series of multiplications. I understand it can be surprising/confusing at first, because most other languages don’t make such a difference (mainly because integers are often implicitly converted to … Read more
Regarding “Haskell’s equally powerful inference”, I don’t think Haskell has to deal with OO-style dynamic subtyping (type classes can do some similar stuff, but type classes are easier to type/infer) method overloading (type classes can do some similar stuff, but type classes are easier to type/infer) That is, I think F# has to deal with … Read more
Perl style regex matching let (=~) input pattern = System.Text.RegularExpressions.Regex.IsMatch(input, pattern) It lets you match text using let test = “monkey” =~ “monk.+” notation.
The point-free style is considered by some author as the ultimate functional programming style. To put things simply, a function of type t1 -> t2 describes a transformation from one element of type t1 into another element of type t2. The idea is that “pointful” functions (written using variables) emphasize elements (when you write \x … Read more