Formal comment #140 (enhancement)

Max and min with zero arguments
Reported by: 	John Cowan
Version:	5.92

Summary: Max and min should be allowed to have zero arguments.

In R5RS the max and min functions must take at least one argument,
because there is no universal maximum or minimum. In R6RS, however, we
have +0.inf and -0.inf. I suggest, therefore, that (max) => -0.inf and
(min) => +0.inf. This also allows multiple-argument max and min to be
defined using a fold primitive ver two-argument versions.

Alex Shinn's remarks on #scheme inspired this comment, but he is not
to be held responsible for it.


RESPONSE:

No exact number is an identity for max or min, so there is no
obvious result for them to return when called with no arguments.

Defining (max) and (min) to return +0.inf and -0.inf would not
allow them to be defined in the obvious way using the fold primitive
over a two-argument restriction, since that definition would
always return an inexact result, contrary to the specifications
of max and min.

Creating unique special cases in which max and min return
inexact arguments would create exceptions to the rule stated
in section 9.9.1 that requires them to return an exact result
provided all of their arguments are exact.

There does not seem to be any compelling reason to extend max
and min to zero arguments that would offset these identifiable
problems.