Can I use dynamic types in F#?

Question

.net4.0

mytest.py

def Add (a, b):
    return a+b

I can use it in C# 4, like this:

        ScriptRuntime runtime = Python.CreateRuntime();
        dynamic script = runtime.UseFile("mytest.py");

        Console.WriteLine(script.Add(1, 3));

But, how can I use dynamic in F#?

open System
open Microsoft.Scripting.Hosting
open IronPython.Hosting

let call a b=
    let runtime = Python.CreateRuntime()
    let script = runtime.UseFile("mytest.py")
    script.Add(a,b)

Answer 1

There is a module FSharp.Interop.Dynamic, on nuget that implements the dynamic operator using the dlr. So That:

open System
open Microsoft.Scripting.Hosting
open IronPython.Hosting
open EkonBenefits.FSharp.Dynamic

let call a b=
    let runtime = Python.CreateRuntime()
    let script = runtime.UseFile("mytest.py")
    script?Add(a,b)

It has several advantages over a lot of the snippets out there.

• Performance it uses Dynamitey for the dlr call and Dynamitey implements caching of the callsites and is a PCL library
• Handles methods that return void, you'd get a binding exception if you didn't discard results of those when the binder was setup.
• The dlr handles the case of calling a delegate return by a function automatically, impromptu fsharp will also allow you to do the same with an FSharpFunc

• Adds an !? prefix operator to handle invoking directly dynamic objects and functions you don't have the type at runtime.

  It's open source, Apache license, you can look at the implementation and it includes unit test example cases.