...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
An iterator of constant, decoded characters.
using iterator = see-below;
This iterator is used to access the encoded string as a bidirectional range of characters with percent-decoding applied. Escape sequences are not decoded until the iterator is dereferenced.