Sorting according to a primary and secondary criterion

[bearophile]

Joseph Rushton Wakeling:

> Is there a standard, accepted approach for this kind of sort 
> with primary/secondary criterion?

There are various ways to do it. One way is to use a stable sort 
and sort the data two or more times.

Another way is to use something like this, but this needs some 
memory:

idx.schwartzSort!(i => tuple(arr1[i], arr2[i]));

But often the most efficient way is to use sort() with a 
comparison function that takes in account all your sorting 
criteria.

Bye,
bearophile