On Thu, Mar 25, 2010 at 20:01, Greg Ewing <greg.ewing@canterbury.ac.nz> wrote:
So we have three correctness-preserving possibilites:
1) Always raise an exception as soon as a NaN is produced.
2) Propagate NaNs through arithmetic but raise an exception when attempting to compare them.
This forces you to explicitly compare them when desired, but it's even simpler than I realized (and doesn't require new functions). def func(a, b): if not isnan(a) and not isnan(b) and a == b: return 1.0 return math.sin(a*b)**(a-b) All it requires is you check for NaN before your normal comparison. It's even backwards compatible with Python 2.6! If that example is a little verbose for you, just make isnan take multiple arguments and return true if any are NaN.
3) Return a NaB when comparing NaNs, and raise an exception when attempting to branch on a NaB.
-- Adam Olsen, aka Rhamphoryncus