C# 4.0 / dynamic / operators

Mon, 03 Nov 2008 16:00:49 Z

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();

}

Marc [C# MVP]

C# 4.0 / dynamic / operators

Tue, 04 Nov 2008 05:53:41 Z

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).

C# 4.0 / dynamic / operators

Tue, 04 Nov 2008 07:44:33 Z

Cheers

Marc [C# MVP]