Using XLISP-STAT With NT Emacs on Win32

The Win32 distribution now includes a command line client xlsclient. This client reads expressions from standard input, uses DDE to ask XLISP-STAT to evaluate the expressions and print any results, and then uses DDE to retrieve the output, which is then displayed on standard output. The main purpose of this client is to allow XLISP-STAT to be run under NT Emacs. The client assumes that XLISP-STAT is already running; it does not try to start XLISP-STAT itself; you must do that before using the client.

To use this mechanism with the standard inferior Lisp mode, you need to tell emacs to use xlsclient as its inferior-lisp-program, for example by setting it in your .emacs file. You can then run the client with M-x run-lisp.

You can also run XLISP-STAT under ESS mode. To do this, during the installation process for ESS define the variable inferior-XLS-program-name in ess-site.el with

(setq-default inferior-XLS-program-name "xlsclient")

using a full path for the client if it is not in your search path.

The DDE-based approach is simple, but has a few drawbacks:

• It is not possible to execute an expression that reads from standard input. Attempting to read from standard input will give an end of file error message.
• It is not possible to interrupt execution of an expression from Emacs. To interrupt execution you need to switch to the XLISP-STAT listener and signal an interrupt with Control-BREAK.
• Special variable bindings and assignments in the listener affect ones in the client and vice versa.

Most of these issues can only really be resolved properly by having proper threads at the Lisp level and having the Listener and the command line processed by different threads

But aside from those minor issues, this approach seems to work reasonably well.