[F-0X]

The major examples are parts of the stdlib which offer higher-level pipelines (some answers here indicate the need for such things to be very flexible in their return values to allow this, but this is not a priori obvious - Java manages similar functionality with just the Stream<T> class after all).

In this (and the sibling pages in algorithm) nearly every entry is listed as either "template" or "auto" relhttps://dlang.org/phobos/std_algorithm_iteration.html

[aldacron]

D's classes and interfaces are much like Java's, so it's possible and easy to write functions that express return types like that. It's also quite restrictive for generic programming. D's metaprogramming features are much more powerful. That means a template can return different types that do not conform to a single, easily-expressed interface. The std.algorithm package is built on that concept.