opPow, opDollar

[Andrei Alexandrescu]

Robert Jacques wrote:
> I'd recommend rolling that into a basic statistics struct containing 
> common single pass metrics: i.e. sum, mean, variance, min, max, etc.

Well the problem is that if you want to compute several one-pass 
statistics in one pass, you'd have to invent means to combine these 
functions. That ability is already present in reduce, e.g. reduce(min, 
max)(range) yields a pair containing the min and the max element after 
exactly one pass through range.

Andrei