Ranges are a major new enhancement to the way collections can be manipulated in C++, providing a declarative interface that is easier and safer to use than traditional iterators. Ranges were also one of the most challenging libc++ features to implement due to the need for extensive changes across the entire implementation of STL containers and algorithms. In this talk, I will provide insights into the novel design and implementation strategies we employed in libc++ to minimize code duplication and create a robust, well-tested implementation.