std::less_equal (3) - Linux Manuals

std::less_equal: std::less_equal

NAME

std::less_equal - std::less_equal

Synopsis

Defined in header <functional>
template< class T > (until C++14)
struct less_equal;
template< class T = void > (since C++14)
struct less_equal;

Function object for performing comparisons. Unless specialized, invokes operator<= on type T.

Specializations

A specialization of std::less_equal 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_equal<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_equal when T is not specified, which leaves the parameter types and return type to be deduced.

                 function object implementing x <= y deducing argument and return types (since C++14)
less_equal<void> (class template specialization)

Member types

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

Member functions

           checks if the first argument is less than or equal to the second
operator() (public member function)

 std::less_equal::operator()

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 if lhs is less than or equal to rhs.

Parameters

lhs, rhs - values to compare

Return value

true if lhs <= rhs, false otherwise.

Exceptions

(none)

Possible implementation

  constexpr bool operator()(const T &lhs, const T &rhs) const
  {
      return lhs <= rhs;
  }