Stop Spam Harvesters, Join Project Honey Pot

Setup

I used Mono 2.4 and MonoDevelop 2.0 (the binary download under Mac OS X, built from sources for Debian Lenny x86-64) and the DLR from Subversion (revision 23071).

For the DLR to build I had to make some changes to the project files:

find . -name '*.csproj' | xargs perl -i -pe 's/\Q;$(SignedSym)\E//' -- 
find . -name '*.csproj' | xargs perl -i -ne '/<TreatWarningsAsErrors>/ || print' -- 

naturally the same changes can be performed from the project settings dialog inside MonoDevelop, but the above one-liners are way quicker.

The DLR compiles just fine from inside MonoDevelop, just open Src/Codeplex-DLR.sln, expand "Runtme" and build Microsoft.Scripting.ExtensionAttribute, Microsoft.Scripting.Core and Microsoft.Scripting. I have not tried to build the rest of the projects (examples, IronPyton and IronRuby).

Hello world

using System;
using Microsoft.Linq.Expressions;

namespace HelloWorld
{
    class MainClass
    {
        public static void Main(string[] args)
        {
            // get the MethodInfo for the method System.Console.WriteLine(string)
            var write_line = typeof(System.Console).GetMethod("WriteLine", new Type[] { typeof(string) });
            // construct the expression tree for System.Console.WriteLine("Hello, world!")
            var exp = Expression.Lambda(
                        Expression.Call(write_line,
                                        Expression.Constant("Hello, world!")));
            // compile the expression and call the generated code
            exp.Compile().DynamicInvoke();
        }
    }
}

While the program output is nothing impressive, I find the ability to dynamically compile expression trees pretty impressive. Even more impressive is that expression trees can work both for translating ASTs (they have blocks, conditional expressions, loops) and for compiling basic blocks (using goto).