From the Floating-Point Guide:
What can I do to avoid this problem?
That depends on what kind of
calculations you’re doing.
- If you really need your results to add up exactly, especially when you
work with money: use a special decimal
- If you just don’t want to see all those extra decimal places: simply
format your result rounded to a fixed
number of decimal places when
- If you have no decimal datatype available, an alternative is to work
with integers, e.g. do money
calculations entirely in cents. But
this is more work and has some
Note that the first point only applies if you really need specific precise decimal behaviour. Most people don’t need that, they’re just irritated that their programs don’t work correctly with numbers like 1/10 without realizing that they wouldn’t even blink at the same error if it occurred with 1/3.