[IronPython] Building via AST

[Justin Chase]

Ok so I'm wondering if I'm perhaps using the wrong words to try to say what
I mean. Because when I look into the IronPython source code I see a class
called Microsoft.Scripting.Generation.TypeGen (
http://ironpython.codeplex.com/SourceControl/changeset/view/65328#1011039).
Which appears to be code for generating a .net type contrary to your
response. Am I misinterpreting that?

Thanks for your examples below but that is about as far as I have gotten
already, what I need is a way to actually generate types and instances
members. And I was just looking at the ILGen class and all it's interesting
helpers but what I'd really love to find is a way to generate this by just
giving it an AST (including "this" references) instead of having to mess
around with IL (hasn't this been solved already??).

I know that Python has a "class" construct and that if I compile scripts I
can create instances of these objects, does this translate into actual .net
types under the hood? Or something else? Can you add attributes or
annotations to these classes for example? For my grand finale what I would
really like to do is to generate types that implement interfaces and load
them via MEF (by means of the Export attribute). Is this just the wrong way
to be thinking about this entirely? Or am I just missing something?


On Mon, Apr 12, 2010 at 3:33 PM, Dino Viehland <dinov at microsoft.com> wrote:

>  Nope – the DLR doesn’t have any support for building .NET types – dynamic
> or otherwise.  If you’d like to just build an object which behaves
> dynamically I’d suggest looking at DynamicObject.  You can just subclass it
> and override various Try* methods and you’ll have a dynamic object.
>
>
>
> If you really do need to do ILGen into a type, and as long as you’re
> building only static methods, you can use expression trees via
> Lambda<T>.CompileToMethod (unfortunately currently instance methods are not
> supported).  Here’s an example of that:
>
>
>
> using System;
>
> using System.Linq.Expressions;
>
> using System.Reflection;
>
>
>
> class Foo {
>
>     public static void Main(string[] args) {
>
>         var asm = AppDomain.CurrentDomain.DefineDynamicAssembly(new
> AssemblyName("foo"), System.Reflection.Emit.AssemblyBuilderAccess.Save);
>
>         var module = asm.DefineDynamicModule("foo.dll");
>
>         var type = module.DefineType("TestType");
>
>
>
>         var param1 = Expression.Parameter(typeof(Foox), "arg1");
>
>         var param2 = Expression.Parameter(typeof(Foox), "arg2");
>
>         var method = type.DefineMethod("TestMethod",
> MethodAttributes.Public | MethodAttributes.Static);
>
>
>
>         Expression.Lambda<Func<Foox, Foox, bool>>(
>
>             Expression.Equal(param1, param2),
>
>             new[] { param1, param2 }
>
>         ).CompileToMethod(method);
>
>         type.CreateType();
>
>         asm.Save("foo.dll");
>
>     }
>
> }
>
> enum Foox {
>
>     Bar,
>
>     Baz
>
> }
>
>
>
> *From:* users-bounces at lists.ironpython.com [mailto:
> users-bounces at lists.ironpython.com] *On Behalf Of *Justin Chase
> *Sent:* Monday, April 12, 2010 1:21 PM
> *To:* users at lists.ironpython.com
> *Subject:* [IronPython] Building via AST
>
>
>
> Suppose I would like to build an AST programmatically and compile that into
> an assembly dynamically (meaning an assembly flagged with RunAndCollect)
> from C#. How would I do that with IronPython's help? I do not what to author
> Python code and compile that I would like to just deal directly with the
> AST.
>
>
>
> Currently I have working code where I'm using System.Linq.Expression
> namespace to build statements and expressions into delegates but what I
> would like is to leverage the DLR to build dynamic types as well (without
> having to use ILGenerator preferably). Is this possible today?
>
>
> --
> Justin Chase
> http://www.justnbusiness.com
>
> _______________________________________________
> Users mailing list
> Users at lists.ironpython.com
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>
>


-- 
Justin Chase
http://www.justnbusiness.com
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