#include <LinearMap.hpp>
template<class Key, class Relation>
requires(Relation r, Key a, Key b) { { std::invoke(r, a, b) } -> std::same_as<std::strong_ordering>; }
|| requires(Relation r, Key a, Key b) { { std::invoke(r, a, b) } -> std::convertible_to<bool>; }
Definition LinearMap.hpp:13