Questions about the slice operator

[Jacob Carlborg]

On 2012-04-04 15:01, Simen Kjærås wrote:

> Actually, I've thought a little about this. And apart from the tiny
> idiosyncrasy of $, a..b as a more regular type can bring some
> interesting enhancements to the language.
>
> Consider a..b as simply a set of indices, defined by a start point and
> an end point. A different index set may be [1,2,4,5], or Strided!(3,4).
>
> An index set then works as a filter on a range, returning only those
> elements whose indices are in the set.
>
> We can now redefine opIndex to take either a single index or an index
> set, as follows:
>
> auto opIndex(S)(S set) if (isIndexSet!S) {
> return set.transform(this);
> }
>
> For an AA, there would be another constraint that the type of elements
> of the index set match those of the AA keys, of course. Other containers
> may have other constraints.
>
> An index set may or may not be iterable, but it should always supply
> functionality to check if an index is contained in it.
>
> With this framework laid out, we can define these operations on arrays,
> and have any array be sliceable by an array of integral elements:
>
> assert(['a','b','c'][[0,2]] == ['a', 'c']);

I don't think I really understand this idea of an index set.

-- 
/Jacob Carlborg