Iterating over multiple collections in parallel

[Manfred_Nowak]

Koroskin Denis wrote:

> List!(int) a, b, c;
[...]
> which one would you prefer?

Still

   c= a .+ b;

To do componentwise operations imposes some requirements for the 
involved types. These are at least:
- an order on the elements, and
- definition(s) for the operation(s) on the elements

If an opApply cannot be interpreted as representing an ordering, than 
your List!-example will fail badly.

-manfred