Hi Nathaniel,

Thanks for the detailed reply; it helped a lot to understand how one could, indeed, have dtypes contain units. And if one had not just on-the-fly conversion from int to float as part of an internal loop, but also on-the-fly multiplication, then it would even be remarkably fast. Will be interesting to think this through in more detail.

Still think subclassing ndarray is not all *that* bad (MaskedArray is a different story...), and it may still be needed for my other examples, but perhaps masked/uncertainties do work with the collections idea. Anyway, it now makes sense to focus on dtype first.

Thanks again,

Marten