# std::less_equal

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< cpp‎ | utility‎ | functional

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:

- std::less, std::greater, std::less_equal, and std::greater_equal, when the template argument is a pointer type or void (since C++14)

`std::ranges::equal_to`, `std::ranges::not_equal_to`, `std::ranges::less`, `std::ranges::greater`, `std::ranges::less_equal`, `std::ranges::greater_equal`, and std::compare_three_way | (since C++20)

### Specializations

less_equal<void> (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

less | function object implementing x < y (class template)
ranges::less_equal (C++20) | function object implementing x <= y (class)

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