Version 3 of Eagle: Re-implementing Tcl in C#

Updated 2008-10-23 12:53:15 by LV

MC's notes on Joe Mistachkin's Tcl2008 talk regarding his re-implementation of Tcl in C#.

JJM -- The full paper and slides will also be available (soon) from the project web site. Also see Eagle

(I missed the first slide...)

Notable features:

  • Integrates with Microsoft's Common Language Runtime (CLR), Tcl/Tk, native libraries
  • Supports interactive debugging, script cancellation; read-only variables, commands; interpreter-wide variable tracing; closures; Unicode (UCS-2)

Missing:

  • No Tk commands
  • No argument expansion syntax
  • No namespace support (yet)
  • No binary, fblocked, fcopy, fileevent, format, glob, history, memory, can or trace commands
  • No registry or DDE commands
  • No asynchronous input/output
  • No server sockets
  • No slave interpreters, hidden commands, aliases, hence no Safe Tcl
  • No http, msgcat, or tcltest packages
  • For the open command, command pipelines and serial ports are not yet supported
  • For the exec command, Unix-style input/output redirection and command pipelines are not supported

Compiles with Visual Studio 2005, 2008 and/or .NET framework compiler. Ran a demo eagle console. "#show" special command to show output helpful for debugging

 % set x [[object create System.Int32]]
 System#Int32#216
 % object invoke $x ToString
 0
 % set y [[object create -alias System.Int32]]
 ...

Eagle, being managed code, has access to all the .NET framework. Joe ran a demo that used .NET calls to instantiate a Windows form.

Within Eagle: [tcl find] finds installed versions of Tcl. [tcl load] can load them. Eagle can load Tcl via a .dll; then package require Tk. Thus Tk and winforms can be mixed.

Calling foreign functions:

 set z [[library declare -functionname GetUserNameA -returntype Boolean -paramatertypes [[list intptr uint32&]] -charset ansi -module ...]]

Eagle takes a different approach to some things than Tcl. Semantically compatible at the script level. Radically different underneath the hood. No interp->result. Interpreters in Eagle have no thread affinity; can be used from any thread.

Question from the chat: "How easy is it to embed Eagle into a C# application?" Answer: examples of doing that come with the distribution. Walked through a simple example.

Question: What is the benefit of rewriting versus wrapping? Answer: Requirement was to implement the scripting language totally in 100% managed mode code.

Downloadable from http://eagle.to

One question was "are the items above listed as missing a matter of limited resources in writing the code, or a limit of the environment" and the answer was that many of the items on the missing list are just a matter of not having enough time yet to write the code. However, it was my understanding from the reply that there are issues relating to tcl's namespace concept that would be quite difficult to implement.

Tcl 2008 Conference Talks