Floating point output

[Doug Gwyn]

In article <3295 at skye.ed.ac.uk> jeff at aiai.UUCP (Jeff Dalton) writes:
>   A strictly conforming program ... shall not produce output
>   dependent on any unspecified, undefined, or implementation-
>   defined behavior.  [Section 1.7, page 4]

What you need to understand is that this is not intended as a constraint
on output, but rather as a constraint on using nonstandard behavior in
any "essential" way.  For example, since the order of evaluation of the
arguments to a function is unspecified, a strictly conforming program
may have its flow of computation affected by the order, only so long as
the "result" of doing so is the same no matter which order the
implementation chooses.  Note that this is not as strict as a requirement
to not use nonstandard behavior at all.  The actual constraint is phrased
in terms of "output" because that's the closest we could come to saying
"observable effects" in an enforceable way.  Certainly it was not meant
to forbid any use of formatted output of folating-point quantities.