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std::less_equal

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

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

Implementation-defined strict total order over pointers

A specialization of std::less_equal for any pointer type yields the implementation-defined strict total order, even if the built-in <= operator does not.

The implementation-defined strict total order is consistent with the partial order imposed by built-in comparison operators (<=>, (since C++20)<, >, <=, and >=), and consistent among following standard function objects:

(since C++20)

Specializations

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

Member types

Type Definition
result_type (deprecated in C++17)(removed in C++20) bool
first_argument_type (deprecated in C++17)(removed in C++20) T
second_argument_type (deprecated in C++17)(removed in C++20) T

These member types are obtained via publicly inheriting std::binary_function<T, T, bool>.

(until C++11)

Member functions

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

For T which is not a pointer type, true if lhs <= rhs, false otherwise.

For T which is a pointer type, true if lhs does not succeed rhs in the implementation-defined strict total order, false otherwise.

Exceptions

May throw implementation-defined exceptions.

Possible implementation

constexpr bool operator()(const T &lhs, const T &rhs) const 
{
    return lhs <= rhs; // assumes that the implementation uses a flat address space
}

See also

function object implementing x < y
(class template)
(C++20)
function object implementing x <= y
(class)

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https://en.cppreference.com/w/cpp/utility/functional/less_equal