[IronPython] Sympl Language Sample and Walkthrough Document

Bill Chiles billchi at microsoft.com
Thu May 14 02:00:24 CEST 2009

There's a new DLR sample to which I wanted to draw folks' attentions.  There is a small language implementation sample, implemented in both IronPython and C#, with an accompanying walkthrough document.  The code is now on the DLR Codeplex site under ...\Languages\Sympl, and the document is on the "Documents and Specs" page which you can get to from the list of links on the home page.  Under the Sympl directory is also an examples directory with some code written in Sympl, which all runs when you execute Main in program.cs.  The code and document will be in zip files we will produce to go along with the VS Beta1 release coming soon.

Sympl demonstrates how to implement a very simple language using the Dynamic Language Runtime (DLR) as it ships in .NET 4.0.  The goal is to make you aware of how to get started building a language on the DLR.  Sympl does not show production quality rich .NET interoperability and binding logic.  It does walk you through the following:
*       Using DLR Expression Trees (which include LINQ Expression Trees v1) for code generation
*       Using DLR dynamic dispatch caching
*       Building runtime binders
*       Building dynamic objects and dynamic meta-objects
*       Supporting dynamic language/object interoperability
*       Very simple hosting with application supplied global objects
*       Basic arithmetic and comparison operators with fast DLR dispatch caching
*       Control flow
*       Name binding within Sympl
*       Method and top-level function invocation with fast DLR dispatch caching
*       Very simple .NET interoperability for runtime method and operation binding
*       Using the DLR's built-in COM binding
*       Closures
*       Assignment with various left-hand-side expressions
Sympl does not yet demonstrate using any Codeplex-only DLR code such as the DefaultBinder, the faster and nicer .NET reflection trackers (Sympl's is painfully slow and simple), or the common DLR hosting (yet).

A few caveats on the documentation.  First, the walk through document still needs some polishing, but I wanted to get it out to people.  Feel free to send me comments or ask questions.  Second, the document refers to a couple of other documents on our Codeplex site, but we haven't updated some of them since DEC 08.  Those will be updated in the next couple of weeks.  I think the sympl.doc walkthrough is very readable on its own and has all the relevant code snippets included in it as well.  Lastly, while the example is overall reasonably simple, it does demonstrate all the basic concepts of building a language on the DLR with explanations, and therefore, is quite long.  However, the document unfolds in the same way the Sympl language implementation evolved, so it progresses well for incrementally increasing your awareness of how to build a language on the DLR.

Hope you enjoy and find this code and doc helpful!


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