{

I'm still trying different things with Twining. I'd thought about writing some "front end" type experience for usage but it really crystallized as a need when I showed it to a person I know and there seemed to be a disconnect in how it could be used. For me it's natural to set my path environment variable, launch favorite text editor X and then run things from the command line or a script, but it's a nuisance if you're used to a one stop shop for being able to use some tool. And as much as I want language as the focal point in the word "tool" there is something practical in the notion of something you download and click a button to execute with.

Enter Twy, which I pieced together after looking at a few samples of a hosted DLR engine in a Windows Forms app. Now one need not figure out how to install or configure anything, or worry about creating and disposing of script files.

If you want to write something that hosts the DLR engine, take a look first at these samples on Voidspace. There are other samples online if you hunt and peck but be aware that things have changed between the various releases of IronPython. A few gotchas for me:

1. Redirecting standard output:

// where engine references the ScriptEngine type
// and ms references a Stream of some sort
engine.Runtime.IO.SetErrorOutput(ms, Encoding.UTF8);
engine.Runtime.IO.SetOutput(ms, Encoding.UTF8);

Many examples of this are deprecated for the IronPython 2.x beta

2. Referencing classes in mscorlib:

Be aware that doing the following:

import clr
clr.AddReference("System")

is not going to be enough to get types out of mscorlib. Although types will load from System, you'll need to get a reference to the assembly directly if you plan to use it in your hosted engine. I had a little trouble with the StringBuilder but easily resolved it with the following after a tip on the IronPython mailing list.

Assembly assem = Assembly.GetAssembly(Type.GetType("System.Text.StringBuilder"));
scope = engine.CreateScope();
engine.Runtime.LoadAssembly(assem);

3. The only novel thing I did that I didn't see a lot of was loading a module so that you could utilize it with your hosted engine. I added Twining.py to the project and set Visual Studio to copy it to the compile destination. I then have the following code which keeps the module available for later use:

string p = Path.Combine(Environment.CurrentDirectory, "Twining.py");
scope = engine.Runtime.ExecuteFile(p); 

// later on:

ScriptSource source =
    engine.CreateScriptSourceFromString(input,
        SourceCodeKind.Statements);
object res = source.Execute(scope);

All in all not rocket science, it's amazing how much power one has at their fingertips in such a small application. I would love to see other modules, especially ones that define some interesting type of DSL, have utilities like this that let you play around without much effort.

Oh yeah, the project and source. Download it here, I'll clean up a bit more later.

Twy

{

}