Path: utzoo!attcan!uunet!snorkelwacker!bloom-beacon!ZURICH.AI.MIT.EDU!jinx
From: jinx@ZURICH.AI.MIT.EDU ("Guillermo J. Rozas")
Newsgroups: comp.lang.scheme
Subject: Bug in MIT-Scheme
Message-ID: <9003261527.AA27414@zurich.ai.mit.edu>
Date: 26 Mar 90 15:27:15 GMT
References: <1254@tub.UUCP>
Sender: daemon@athena.mit.edu (Mr Background)
Reply-To: jinx@zurich.ai.mit.edu
Organization: The Internet
Lines: 21


    Now let me turn your attention to a real bug in C-Scheme:

    The C-Scheme reader refuses to parse numeric constants like #o-10
    (i.e. a radix followed by a sign followed by digits).  On the other
    hand, it happily accepts something like -#o10.  This must be a bug,
    since the standard clearly says that the radix, like the exactness
    specification, is a prefix (see page 37 of the P1178/D3 or page 32
    of the R^3.99RS), so #o-10 is the correct form, while -#o10 should
    be parsed into two objects, the symbol "-" followed by #o10.


This is not a bug.  The syntax of numbers has changed between R^3RS
and R^3.99RS.  In R^3RS, the sign preceded the radix specifier.  Look
at the production for <number> on page 30.  In R^3.99RS (and
pressumably in the final version, R^4RS), the radix specifier precedes
the sign.  Since R^4RS hasn't been released, nor has the IEEE standard
been approved, you can hardly expect a 1-year-old release of MIT
Scheme to match them.
C-Scheme beta release 7.1 (to be released sometime in the not-too-far
future) matches R^3.99RS in the syntax and semantics of numbers.