Bug?

[Norman Diamond]

In article <9986 at alice.UUCP> ark at alice.UUCP (Andrew Koenig) writes:

>Even if the == operator includes a fuzz factor, it's hard to imagine
>a sensible implementation in which (a-b)==0 is true unless a and b
>are truly identical.

Sorry Mr. Koenig, it's easy to imagine.  Every hardware floating-point
system and most software ones have situations where (a-b)==0 but a != b.

For example (which obviously generalizes), imagine a base-10 system
where exponents can range from -99 to +99.  Let:
  a == 0.100001e-99
  b == 0.100002e-99
Then obviously a != b.  But what happens when (a-b) is computed?
(a-b) --> (-0.000001e-99) --> (-0.100000e-104) --> (0.000000e-99).

-- 
Norman Diamond, Sony Corp. (diamond%ws.sony.junet at uunet.uu.net seems to work)
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