Re: [Q] Portability of <= and >= with real operands

[stt@houdini.camb.inmet.com (Tucker Taft)]

Keith Thompson (kst@aonix.com) wrote:

: In <dewar.849320173@merv> dewar@merv.cs.nyu.edu (Robert Dewar) writes:
: [...]
: > The idea that the use of <= is more portable than either < or =
: > is particular rubbish, I see no possible justification for such a
: > statement, and, unlike the old rule about avoiding equality, I cannot
: > even guess the thought behind this misunderstanding.

: Suppose you've computed two quantities, X and Y, such that X is
: mathematically known to be less than Y, but it may be arbitrarily close.
: Since floating-point is of finite precision, the representations of X
: and Y may be equal.  (For example, X = 0.0, Y = some tiny value which
: underflows to 0.0).  Then X <= Y may reflect the relationship more
: accurately than X < Y.

Are you also saying that X <= Y is somehow "better" than not (X > Y)?
That is truly mysterious, if so.

: Of course, in real life you should analyze the particular case, and you
: may well reach the opposite conclusion, but I'd bet that the original
: rationale for the statement was something like the above.

: Keith Thompson (The_Other_Keith) kst@aonix.com <http://www.aonix.com> <*>

-Tucker Taft   stt@inmet.com   http://www.inmet.com/~stt/
Intermetrics, Inc.  Cambridge, MA  USA