Last week @meejah and I learned that a rust for loop is (edit, this is incorrect, it's always serial! ) automatically unrolled if possible, it's treated like a `map` in Haskell.

BUT, iterators are serial! That is, they're explicitly done in order, one after the other.

When we're working with blocks of data, we'd like to have both options. We want to toggle between "low memory" and "many cores" modes.

Is there a way to do that in #rust ?