Satisfied when a container exposes a size accessor and an indexed element accessor.
Declared in <kernel/bitcoinkernel_wrapper.h>
template<
typename Container,
typename SizeFunc,
typename GetFunc>
concept IndexedContainer = requires(const Container& c, SizeFunc size_func, GetFunc get_func, std::size_t i) {
{ std::invoke(size_func, c) } -> std::convertible_to<std::size_t>;
{ std::invoke(get_func, c, i) }; // Return type is deduced
};