IEEE floating point format

[Karl Heuer]

In article <152 at servio.UUCP> penneyj at servio.UUCP (D. Jason Penney) writes:
>note that with truncating underflow, it is possible to have two floating 
>point values X and Y such that X != Y and yet (X - Y) == 0.0, 
>thus vitiating such precautions as,
>	if (X == Y) error("zero divide"); else something = 1.0 / (X - Y);

I used to have similar problems with the SIMULA compiler on TOPS-10, which
apparently used fuzzy compare even against zero: (example in C notation)
	if (X < 0.0) error("neg sqrt"); else something = sqrt(X);
would die because -1.0E-20 was considered "equal" to zero rather than
negative, yet the sqrt() routine wasn't fooled.  What a pain to work around!

Karl W. Z. Heuer (ima!haddock!karl or karl at haddock.isc.com), The Walking Lint
(What's this doing in comp.lang.c?  Followups to comp.lang.misc.)