F#, namespaces, modules, fs and fsx

Question

I\'m aware of other questions about modules and namespaces in F#, but they\'re not helping me right now.

I\'ve got a project with

Utilities.fs

Answer 1

I'm not an expert with FSI, but some experimentation suggests that namespaces are only supported by #load declarations (not via typical interactions - sending a namespace declaration group to VFSI via Alt-Enter does not work), and that different interactions contribute different 'instances'. For example, with the code file

namespace Foo

type Bar() =
    member this.Qux() = printfn "hi"

namespace Other

type Whatever() = class end

namespace Foo

module M =
    let bar = new Bar()
    bar.Qux()

if I #load it more than once I get e.g.

> [Loading C:\Program.fs]
hi

namespace FSI_0002.Foo
  type Bar =
    class
      new : unit -> Bar
      member Qux : unit -> unit
    end
namespace FSI_0002.Other
  type Whatever =
    class
      new : unit -> Whatever
    end
namespace FSI_0002.Foo
  val bar : Bar

> #load @"C:\Program.fs";;
> [Loading C:\Program.fs]
hi

namespace FSI_0003.Foo
  type Bar =
    class
      new : unit -> Bar
      member Qux : unit -> unit
    end
namespace FSI_0003.Other
  type Whatever =
    class
      new : unit -> Whatever
    end
namespace FSI_0003.Foo
  val bar : Bar

> new Foo.Bar();;
> val it : Foo.Bar = FSI_0003.Foo.Bar

Note that it seems the FSI_0003.Foo.Bar shadowed the FSI_0002 version.

So I'm thinking the part of the F# spec that says

Within a namespace declaration group, the namespace itself is implicitly opened if any preceding namespace declaration groups or referenced assemblies contribute to this namespace, e.g.

namespace MyCompany.MyLibrary 

   module Values1 = 
      let x = 1

namespace MyCompany.MyLibrary 

   // Implicit open of MyCompany.MyLibrary bringing Values1 into scope

   module Values2 = 
      let x = Values1.x

However this only opens the namespace as constituted by preceding namespace declaration groups.

Does not interact with FSI, given FSI's limited understanding of namespaces. Specifically, I expect that the 'second #load' from your example opens e.g. FSI_000N+1's version of the namespace, whereas the prior code was in FSI_000N. Which maybe-explains why the explicit open interaction fixes it; you bring the existing, unshadowed FSI_000N stuff up to the top level before trying to (implicitly) reference it later.

Answer 2

I'm relatively new at this too, but this is what works for me when I'm testing in an fsx file:

#if INTERACTIVE
#r @"C:\Program Files\FSharpPowerPack-2.0.0.0\bin\FParsec.dll"
#r @"C:\Program Files\FSharpPowerPack-2.0.0.0\bin\FParsecCS.dll"
#endif

open FParsec.Primitives  
open FParsec.CharParsers

followed by my code that uses these libraries.