No PRINT-time case conversion switch please!

[Kent M. Pitman <KMP at MIT-MC>]

A switch that decides the case to use at PRINT time can never do the
right thing. it will work ok for expressions like:

USER INPUT	SYSTEM (normal)		SYSTEM (with funny flag)

  X			X			x
  x			X			x

but consider:

 |x|			|x|			x
 |X|			X			x

These can potentially be wrong. Presumably the `normal' column above
is to print out for re-read by a Maclisp style (uppercasing) reader so that

 User inputs |x|
 System outputs |x|
 System later re-reads |x| ;win

 User inputs |X|
 System outputs X
 System later re-reads |X| ;win

Where if you do translation to lowercase at print-time and later think your
output is re-readable acceptably by some implementation that downcases instead
of upcases, you'll find that

 User inputs |x| into uppercasing system
 System outputs |x|
 Lowercasing system later re-reads x ;win

 User inputs |X| into uppercasing system
 System outputs X
 Lowercasing system later re-reads x ;lose!

This is disappointing because the |...| clearly denote the user's intent that
the system not muck with the case of his input. This case actually comes up in
practice. Consider Maclisp programs like:

(defun get-input ()
  (terpri)
  (princ '|INPUT: |)
  (read))

(defun yes? ()
  (memq (readch) '(/y /Y)))

Say what you'd like to about the reasonableness of printing out symbols
instead of strings, or about using readch instead of in-char or whatever.
Those are clearly substandard coding styles, but people sometimes write
substandard code and I think it's very important that we guarantee that 
Lisp READ/PRINT for simple cases like these preserve a certain amount of
semantic content especially when the user has gone to the trouble to type
his symbols with /'s or |...|'s and I don't see any way a PRINT-time decision
can do anything but risk screwing the user.

Anyone who likes to see code in a certain case can write an editor package
(or borrow mine) which upcases or downcases code respecting things vbars,
doublequotes, semicolons, slashes, etc. But I don't think common lisp should
be cluttered with any dwimish notions of automatic case conversion that work
only most of the time ...