Re: Once again a plea for slash

[Guy.Steele at CMU-10A]

I am firmly convinced that the MacLISP-and-sons community would be
much better off if we were to change the "slash" character to something
other than "/".  The sooner we do it, the better.
(1) Sussman and others report that the single greatest stumbling
    block for novice LISP users trying to do numerical tasks is
    remembering to double the "/" for the division operator.  This
    is the only operator of the four standard arithmetic operators
    that does not have the same name used in almost every other
    programming language ("+", "-", "*", "/").
(2) The "/" character is common in English text.  It looks odd to have
    to double it in error messages, etc.  Have you ever written
	(FORMAT T "~S got an I/O error." FOO)
    only to get the error message
	FROBBOZ got an IO error.     ?
    On the other hand, doesn't (FORMAT T "~S got an I//O error." FOO)
    look awfully silly?  (I observe that in a recent note KMP instead
    wrote "I\O" for "I/O" to avoid this difficulty.  I suspect this
    usage looks strange to all except users of APL\360.
(3) I want to push for rational numbers as a standard part of LISP,
    supported along with bignums and floating point, with appropriate
    contagion rules and operations.  An obvious syntax for a rational
    number -- the *only* obvious syntax -- is <fixnum>/<fixnum>,
    for example, 43/17.  One might argue that this syntax could be
    accommodated as an exception anyway, but it would be an awfully
    kludgy exception.
(4) At least one operating system, UNIX, uses the "/" character
    in pathnames.  Other operating systems are likely to emulate
    this, given the popularity of UNIX plus the lower-caseness of "/"!
    For this reason, FRANZ LISP has used "\" as the quote character,
    so that one may use file names like "/usr/gls/win.lsp" rather than
    "//usr//gls//win.lsp".

For all these reasons, I propose that we switch -- and soon -- to "\"
as the standard character quoter.  With the advent of " strings
and | symbols, I think you may be surprised at how few / characters
actually appear in code nowadays.  This will ahve the following
repercussions:
(a) The name of the division function will be "/".  (Actually,
    I further propose that "/" be the universal *correct* division
    operator, which floats (or uses rationals) if necessary to
    give a correct result.  For example, (/ 7 2) => 3.5.  Then let
    "//" be the one which produces integer results for integer
    inputs (or maybe always produces an integer result??).
    The name of remainder would change to "\\", and why don't we
    just flush integer GCD, as it is seldom used?
(b) The #/ syntax would become #\.  Following KMP's recent suggestion,
    #\ could take on the burden of both #/ and #\.
(c) In other situations, / would become \ (for quoting characters).

So how about it, people?  Maybe it's not worth changing MacLISP,
but I predict it would be a well worthwhile investment for LISPM, NIL,
and SPICE LISP.