template<class charT, class traits, class Allocator>
bool operator<=(const basic_string<charT,traits,Allocator>& lhs,
const basic_string<charT,traits,Allocator>& rhs) noexcept;
Returns: lhs.compare(rhs) <= 0.
template<class charT, class traits, class Allocator>
bool operator<=(const charT* lhs,
const basic_string<charT,traits,Allocator>& rhs) noexcept;
Returns: rhs.compare(lhs) >= 0.
template<class charT, class traits, class Allocator>
bool operator<=(const basic_string<charT,traits,Allocator>& lhs,
const charT* rhs) noexcept;
Returns: lhs.compare(rhs) <= 0.