std::less (3) - Linux Man Pages
Defined in header <functional>
template< class T > (until C++14)
template< class T = void > (since C++14)
Function object for performing comparisons. Unless specialized, invokes operator< on type T.
A specialization of std::less for any pointer type yields a strict total order, even if the built-in operator< does not. The strict total order is consistent among specializations of std::less, std::greater, std::less_equal, and std::greater_equal for that pointer type, and is also consistent with the partial order imposed by the corresponding built-in operators (<, >, <= and >=).
If the function call operator of the specialization std::less<void> calls a built-in operator comparing pointers, it yields a strict total order even if the built-in operator< does not. This strict total order is consistent among the specializations std::less<void>, std::greater<void>, std::less_equal<void>, and std::greater_equal<void>, and is also consistent with the partial order imposed by the corresponding built-in operators. (since C++14)
The standard library provides a specialization of std::less when T is not specified, which leaves the parameter types and return type to be deduced.
less<void> (class template specialization)
Type Definition (until C++20)
result_type(deprecated in C++17) bool
first_argument_type(deprecated in C++17) T
second_argument_type(deprecated in C++17) T
operator() (public member function)
bool operator()( const T& lhs, const T& rhs ) const; (until C++14)
constexpr bool operator()( const T& lhs, const T& rhs ) const; (since C++14)
Checks whether lhs is less than rhs.
lhs, rhs - values to compare
true if lhs < rhs, false otherwise.
// Run this code