[Skeime]

Sure, but the inexactness of this modulus operation would not be any more unpredictable than all other kinds of float inexactness. Unless you're talking about the case where you don't know whether your operands are ints or floats. But in that case, there are tons of other unpredictabilities. For example, a + b will round when adding (sufficiently large) integers-represented-as-floats while it will never round for integers. So if you take floating-point math seriously, knowing that you're actually dealing with floats is the first step.

[kragen]

it's true that it would be deterministic, but it would behave differently from the ieee 754 standard, which is at least surprising, which is another sense of the word 'unpredictable'. admittedly, floating-point math that is inexact in a surprising way is not necessarily useless, and to someone who isn't deep into numerical analysis, all floating-point math is inexact in surprising ways

still, it would have real pitfalls if numerical algorithms that give right answers in every other programming language gave subtly wrong answers in python (raising a division-by-zero exception is less troublesome)