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How can I print the type information provided by fsi to the console?
f#

How can I get the type information provided by F# interactive returned programmatically? For example, in the following code:

#light

open System

let myList = [1; 2; 3;]

let f n = n + 1

printfn "%s" (myList.GetType().ToString())

// This returns "Microsoft.FSharp.Collections.List`1+_Cons[System.Int32]"

// How do I get "val myList : int list"?

printfn "%A" (f.GetType())

// This returns "FSI_0026+it@10_1"

// How do I get "val f : int -> int"

Console.ReadLine()

As you can see from the comments, I'd just like to be able to return the same information that the interactive console returns.

This is just an academic exercise, but I was surprised that I didn't get the type notation used by fsi from GetType(). I've tried using reflection, but nothing seems to work.

Thanks!

.

Yes, F# has its own reflection layer than sits on top .NETs reflect to provide the missing pieces where F# has extra concepts that .NET does not (i.e. union types, tuples etc.). Here's a quick sample to get you going:

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#light
open Microsoft.FSharp.Reflection

let myList = [1; 2; 3;]

let t = Type.GetInfo (myList.GetType())

let main() =
    match t with
    | SumType items -> List.iter (fun (name, _) -> printfn "%s" name) items
    | _ -> failwith "not supported"
    
main()
By on 3/3/2008 12:56 AM ()

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