The nicest UX would be to say something like "waiting..." while the denominator is zero. Presenting a zero to the user instead is probably an acceptable short-

The nicest UX would be to say something like "waiting..." while the denominator is zero. Presenting a zero to the user instead is probably an acceptable short-cut, but at the end of the day, it's a UX decision. Which is why it should be handled in explicit if-else code, that lives as close to the UI as possible, rather than being buried in the semantics of basic numerical operators.