Here's one example:

https://dlang.org/phobos/std_algorithm_sorting.html#partitio...

The important line is

auto pieces = partition3(a, 4);

So, what's the type of pieces? The D standard library is written to be generic. And sure enough, that line of code will run. Where it turns into a problem is when you try to do something with it. If pieces is a range, there are certain things you can't do with it. Or maybe you can. Who knows. You'll never learn it from reading the documentation. I've been using D since 2013 and I still struggle with this at times. It's a valid complaint. (D's a great language, but is short on manpower to fix rough edges like this.)