C# 4.0 / dynamic / operators

Question

According to the "New features in CSharp 4.0" doc, dynamic operator dispatch is supported; is this implemented yet?

I was trying to compare to an existing mechanism for using operators with generics (via Expression), but it doesn't compile:

using System;

using System.Diagnostics;

using System.Linq.Expressions;

class Program

{

    static void Main(string[] args)

    {

        TestOperator<int>(10, 2);

        TestDynamic<int>(10,2);

    }

    const int COUNT = 10000000;

    static void TestOperator<T>(T seed, T inc)

    {

        T value = seed;

        Stopwatch watch = Stopwatch.StartNew();

        for (int i = 0; i < COUNT; i++)

        {

            value = OperatorCache<T>.Add(value, inc);

        }

        watch.Stop();

        Console.WriteLine("Operator: {0} ({1})", watch.ElapsedMilliseconds, value);

    }

    static void TestDynamic<T>(T seed, T inc)

    {

        dynamic value = seed;

        //dynamic tmp = inc;

        Stopwatch watch = Stopwatch.StartNew();

        for (int i = 0; i < COUNT; i++)

        {

            // Error 1 Operator '+' cannot be applied to operands of type '::dynamic' and 'T'

            // (note I also tried with dynamic + dynamic, via "tmp")

            value = value + inc; // tmp

        }

        watch.Stop();

        Console.WriteLine("Dynamic: {0} ({1})", watch.ElapsedMilliseconds, value);

    }

    static class OperatorCache<T>

    {

        public static readonly Func<T, T, T> Add;

        static OperatorCache()

        {

            var p1 = Expression.Parameter(typeof(T), "x");

            var p2 = Expression.Parameter(typeof(T), "y");

            var body = Expression.Add(p1, p2);

            Add = Expression.Lambda<Func<T, T, T>>(body, p1, p2).Compile();

        }

    }

}

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Marc [C# MVP]

Answer 1

Chris Burrow mentioned:
If you're wondering what does work for dynamic C# in the CTP build, here's the short story: (a) dynamic method calls, (b) dynamic property gets/sets, and (c) dynamic conversion sites.

So I guess the answer is dynamic operator dispatch is not yet implemented in the CTP, and so value + inc will fail because it's a UnaryOperationAction (the receiver of method call doesn't count, so it's a UnaryOperationAction instead of a BinaryOperationAction).

Answer 2

Cheers

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Marc [C# MVP]