An overload of `splitter` which takes a predicate and no separator but allows you to keep the separator

[jmdavis]

This code works

void main()
{
    import std.algorithm.comparison : equal;
    import std.algorithm.iteration : splitter;
    import std.algorithm.searching : canFind;

    auto range = "16x16+0-2".splitter!(a => "x+-".canFind(a))();
    assert(equal(range, ["16", "16", "0", "2"]));
}

However, there it strips out the separators, so in the case that someone actually wants to keep them, doesn't work. The overloads of splitter which take the separator as an argument give the ability to keep the separator. So, a solution can be hacked together with something like

void main()
{
    import std.algorithm.comparison : equal;
    import std.algorithm.iteration : splitter;
    import std.algorithm.searching : canFind;
    import std.typecons : Yes;

    auto range = "16x16+0-2".splitter!((a, b) => "x+-".canFind(a), Yes.keepSeparators)('x');
    assert(equal(range, ["16", "x", "16", "+", "0", "-", "2"]));
}

but it does involve passing in a separator that's ignored, which isn't ideal.

I don't know how often it would actually be useful to pass both a predicate and keep the separator, but it did come up in discord when someone wanted to do it, and since the other overload lets you keep the separator, arguably the one that doesn't take an explicit separator should as well.

Either way, it's here as a possible enhancement.