Re: Real numbers

[Tony Graham <tgraham@xxxxxxxxxxxxxxxx>]

At 13 Aug 1997 20:20 +0100, Dave Love wrote:
 > >>>>> "Tony" == Tony Graham <tgraham@xxxxxxxxxxxxxxxx> writes:
 > 
 >  Tony> Where is the definition of real numbers?  What should the
 >  Tony> result be of (number? (sqrt -1)) if DSSSL does not support
 >  Tony> complex numbers?
 > 
 > Probably a domain error would be most appropriate (typically most
 > useful), but `(sqrt -1)' might return NaN which should answer #t to
 > `number?' even though it's `not a number' in the IEEE 754 sense.  You
 > can find both behaviours in Scheme systems.

I read further and found (section 8.5.7.20) that sqrt should signal an
error if its argument is negative.

I still don't know DSSSL's (or Scheme's) definition of a real number
("The Scheme Programming Language" by Dybvig just assumes you
understand about real and complex numbers), and I can't think of an
argument that would return different values for real? and number?
since the only numbers in DSSSL systems are real numbers.

Regards,


Tony Graham
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Tony Graham
Mulberry Technologies, Inc.                         Phone: 301-315-9632
17 West Jefferson Street, Suite 207                 Fax:   301-315-8285
Rockville, MD USA 20850                 email: tgraham@xxxxxxxxxxxxxxxx
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