I'm reading the "Pony" tweet quoted in TFA and your comment and I'm left very puzzled: is that really that common to want x / 0 == 0 ? In practice where does that crop up?

You say that you frequently have to write your little shim but honestly I don't remember writing code like that in recent memory.

You talk about progress bars, I suppose it makes sense if you somehow try to copy 0 elements for instance, and you end up dividing by zero when computing the progress, like:

    pos_percent = (copied_elems * 100) / total_elems

And both copied_elems and total_elems are zero. But in this case wouldn't you want the computation to return 100% instead of zero?

It's also a bit odd because it introduces a discontinuity: as the divisor goes towards zero the result of the operation gets greater until it reaches exactly zero and it yields 0. Wouldn't it make more sense to return INT_MAX (for integers) or +inf for floats? If you're writing a game for instance it might work better.

I guess it just goes to show that it probably makes a lot of sense to leave it undefined and let people write their own wrapper if necessary to do what works best for them in their given scenario.