Added TEACH;TS XLISP -- teaches lisp.

Resolves #377.

doc/programs.md

@@ -289,6 +289,7 @@
 - VTTIME, display running time on the terminal.
 - VV/VJ/DETREE, list jobs.
 - XHOST, tool for replacing host nicknames with real hostnames.
+- XLISP, teaches Lisp -- part of TEACH system.
 - WA, a Wumpus advisor game.
 - WEBSER, HTTP server.
 - WHAT, humorous quips to various "what" questions.

doc/teach/-read-.-this-

@@ -0,0 +1,5 @@
+
+
+This directory is maintained by RWK and KMP. It is used for the Lisp teacher
+and related things. If you think it is taking up too much space, please contact
+one of us before moving or deleting anything. 

doc/teach/teach.bugs

@@ -0,0 +1,21 @@
+Date: 16 April 1984 16:14-EST
+From: Kent M Pitman <KMP @ MIT-MC>
+Subject:  teach-emacs
+To: RREINER @ SIMTEL20
+cc: BUG-TEACH @ MIT-MC
+In-reply-to: Msg of Tue 3 Apr 84 11:30:15-MST from Robert Reiner <RREINER at SIMTEL20.ARPA>
+
+    Date: Tue 3 Apr 84 11:30:15-MST
+    From: Robert Reiner <RREINER at SIMTEL20.ARPA>
+    To:   bug-teach at MIT-MC.ARPA
+    Re:   teach-emac
+
+    We use an Otrona Attache as a terminal with the Softcom program.  The
+    Softcom progjram uses the escape character to interruopt the terminal
+    program and to store buffers etc.  Any suggestions oon how to use
+    Teach-EMacs
+
+No. I suggest you get another kind of terminal. You will have troubles with
+more than just TEACH-EMACS if you cannot send an escape character through.
+-kmp
+

doc/teach/to-do.7

@@ -0,0 +1,67 @@
+;;; -*- Mode:TEXT; -*-
+
+WORK TO BE DONE ON XTEACH
+
+0. numbered dumps for...
+1. fix files
+
+2. Think about handlers for the control characters that do fun things
+like explain that they've typed ^B or ^D or whatever and ask them if
+they are losing utterly or have some idea of what magic they've
+tripped over.
+
+3. Think about having lessons that enable features of the system so
+that once they're at a certain level of sophistication, they can hack
+fun things like breakpoints and stuff.
+
+4. Make the lessons go lots farther so that these are fun things to
+think 'bout.
+
+5. RENAMEF and back copies. KMP says:
+
+     I suspect the right thing is to write a subroutine which reaps
+     all but the most recent version and/or to set the generation
+     retention count of that file to 1.
+
+6. MORE stuff...
+
+ (defvar **more**-chars nil)
+ (defmacro bind-**more**-chars (specs &body body)
+   `(let ((**more**-chars (append **more**-chars ',specs))) ;or some such
+      ,@body))
+ (defun some-lesson-part ()
+   (bind-**more**-chars ((#^A abort-lesson "Abort lesson"))
+	  ...cruft...))
+ (defun **maybe-more** (...)
+   (cond ...
+	 ((assq c **more**-chars)
+	  (funcall (assq c **more**-chars)))
+	 ...
+	 (flag
+	  (format t ...hair...))))
+ the hair comes from what happens if you do 
+  (bind-**more**-chars ((#^A thing1))
+    (bind-**more**-chars ((#^A thing2))
+      ...))
+ to get (SPACE=Continue,RUBOUT=Flush,^A=thing2)
+ and not thing1. the reason i suggest append is you can do
+ (do ((l **more**-chars (cdr l)))
+     ((null l))
+   (cond ((not (assq (caar l) (cdr l))) ;no other awaits us
+	  (format outstream "..."))))   ;so type out info...
+
+7. Should we give them a script file to play with? (mention it
+in LESSON INFO, if so.
+
+8. Lessons--
+
+INFO
+ is there to be a special lisp for them, or just xteach itself?
+
+EVAL
+ makes the claim that evaluation will be talked about "in greater detail"
+later. Hah!
+ application does not seem to be addressed any place.
+
+OBJECT
+ says we'll deal with uses of TYPEP in later lessons. we don't.