[Python-Dev] Expert floats (original) (raw)

Andrew Koenig ark-mlist at att.net
Wed Mar 31 15:00:42 EST 2004

Binary fp loses in these common cases just because the true inputs can't be represented, and the number printed at the end isn't even the true result of approximately adding the approximated inputs. Decimal easily avoids all of that.

Well, some of it. It still doesn't avoid 1E50 + 1E-50 == 1E50, for example.

> Why are you not arguing against decimal floating-point if your goal > is to expose users to the problems of floating-point as early as > possible?

The overwhelmingly most common newbie binary fp traps today are failures to realize that the numbers they type aren't the numbers they get, and that the numbers they see aren't the results they got.

Then how about giving a warning for every floating-point literal that cannot be exactly represented in binary?

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