"fold": a replacement for "reduce"

[bearophile]

monarch_dodra:

> So my vote goes to this solution.
>
> //----
> uint[] foo3(in uint[][] X)
> {
>     assert(!X.empty)
>     auto seed = X.front.dup;
>     X.popFront();
>     return reduce!((i, j) => zip(i, j)
>                              .map!(kw => kw[0] | kw[1])
>                              .array)
>                   (seed, X);
> }
> //----
>
> I re-wrote it that way: It's a bit longer, but a bit more 
> generic in terms of customizing your seed.

OK, thank you. So the price for that "in" is to use a dup :-) (Or 
use lower level code).

Bye,
bearophile