f#

问题 I just ran across http://frankniemeyer.blogspot.com/2010/04/minimalistic-native-64-bit-array.html Which contains the line (# "sizeof !0" type('T) : nativeint #) I believe the technical phrase is "what the heck?" I have never in my (~8 months) of F# programming run across something even resembling that... FSI tells me something about deprecated constructs, used only for F# libs... And google with (# does uh...well, not much Any direction in this? 回答1: This is the notation for inline IL

问题 Using the following continuation monad: type ContinuationMonad() = member this.Bind (m, f) = fun c -> m (fun a -> f a c) member this.Return x = fun k -> k x let cont = ContinuationMonad() I fail to see why the following gives me a stack overflow: let map f xs = let rec map xs = cont { match xs with | [] -> return [] | x :: xs -> let! xs = map xs return f x :: xs } map xs id;; let q = [1..100000] |> map ((+) 1) While the following doesn't: let map f xs = let rec map xs = cont { match xs with |

问题 Using the following continuation monad: type ContinuationMonad() = member this.Bind (m, f) = fun c -> m (fun a -> f a c) member this.Return x = fun k -> k x let cont = ContinuationMonad() I fail to see why the following gives me a stack overflow: let map f xs = let rec map xs = cont { match xs with | [] -> return [] | x :: xs -> let! xs = map xs return f x :: xs } map xs id;; let q = [1..100000] |> map ((+) 1) While the following doesn't: let map f xs = let rec map xs = cont { match xs with |

问题 Using the following continuation monad: type ContinuationMonad() = member this.Bind (m, f) = fun c -> m (fun a -> f a c) member this.Return x = fun k -> k x let cont = ContinuationMonad() I fail to see why the following gives me a stack overflow: let map f xs = let rec map xs = cont { match xs with | [] -> return [] | x :: xs -> let! xs = map xs return f x :: xs } map xs id;; let q = [1..100000] |> map ((+) 1) While the following doesn't: let map f xs = let rec map xs = cont { match xs with |

问题 Does the F# library include a priority queue? Else can someone point to me an implementation of priority queue in F#? 回答1: There's an implementation of a binomial heap here which is a common data structure for implementing priority queues. 回答2: Take a look at http://lepensemoi.free.fr/index.php/tag/data-structure for a whole bunch of F# implementations of various data structures. 回答3: FSharpx.Collections includes a functional Heap collection https://github.com/fsharp/fsharpx/blob/master/src

问题 Here's what can be done in C# - var two = 2; System.Linq.Expressions.Expression<System.Func<int, int>> expr = x => x * two; expr.Compile().Invoke(4); // returns 8 I wish to do the precise equivalent in F#. Here's what I tried, but did not compile - let two = 2 let expr = (fun x -> x * two) : System.Linq.Expressions.Expression<System.Func<int, int>> expr.Compile().Invoke(4) // desired to return 8 Perhaps predictably, compilation fails on line 2 with the following error - "This function takes

问题 I am wondering what are the good practices in using type provider in F#, I have an XML file (25Mo+), I thought it will not be an issue but my Visual Studio is suffering a lot loll. What is usually the good practice, to define a complete template of the XML with the minimum of data and Load the content later ? And if we load a big file with optional node, the type will be inferred by the most complete one ? Thanks 回答1: The XmlProvider type provider is based on XDocument (LINQ to XML), so it

问题 We're using Fake and I'd like to run DotCover after our Build target. It's alway telling me: C:\Users\xxxxx\Dev>FAKE\tools\Fake build.fsx F# Interactive for F# 3.1 (private) Freely distributed under the Apache 2.0 Open Source License For help type #help;; > [Loading C:\Users\xxxxx\Dev\build.fsx] build.fsx(8,1): error FS0039: The value or constructor 'DotCoverNUnit' is not defined My short simple "test" script #r @"FAKE/tools/FakeLib.dll" open Fake DotCoverNUnit dotCoverOptions nUnitOptions

问题 We're using Fake and I'd like to run DotCover after our Build target. It's alway telling me: C:\Users\xxxxx\Dev>FAKE\tools\Fake build.fsx F# Interactive for F# 3.1 (private) Freely distributed under the Apache 2.0 Open Source License For help type #help;; > [Loading C:\Users\xxxxx\Dev\build.fsx] build.fsx(8,1): error FS0039: The value or constructor 'DotCoverNUnit' is not defined My short simple "test" script #r @"FAKE/tools/FakeLib.dll" open Fake DotCoverNUnit dotCoverOptions nUnitOptions

问题 let h = dict [(1, 2), (3, 4)] Console.WriteLine(h.Count) for i in h do Console.WriteLine(i) gives me 1 [(1, 2), (3, 4)] Two questions. Firstly, why does iterating over a dict give me back a sequence which only has 1 item, the dict itself? There is probably some logic behind this that will also affect other things I end up trying to iterate over. What does this mean for all the other Seq members exposed by dict (Any(), All(), Aggregate(), etc.)? Secondly, is there a good way to iterate over