Rounding errors using doubles?

[Joe Buck]

> On a Pentium II, the following code gives an incorrect result when using
> doubles, but a correct result when using floats:

Take it to a beginner's programming group.  (Hint: .86 can't be
represented exactly in floating point, the nearest IEEE float is
a hair above .86, the nearest IEEE double is a hair below .86;
in C, conversion from float or double to integer truncates, it does not
round).

> This is VERY bad for our software.

Any compiler will be very bad for your software, until you learn how
to use floating point.