std::rel_ops::operator!=,>,<=,>=

Header: <utility>

Given a user-defined operator== and operator< for objects of type T, implements the usual semantics of other comparison operators.

# Declarations

template< class T >
bool operator!=( const T& lhs, const T& rhs );

(deprecated in C++20)

template< class T >
bool operator>( const T& lhs, const T& rhs );

(deprecated in C++20)

template< class T >
bool operator<=( const T& lhs, const T& rhs );

(deprecated in C++20)

template< class T >
bool operator>=( const T& lhs, const T& rhs );

(deprecated in C++20)

# Parameters

lhs: left-hand argument
rhs: right-hand argument

# Notes

Boost.operators provides a more versatile alternative to std::rel_ops.

As of C++20, std::rel_ops are deprecated in favor of operator<=>.

# Example

#include <iostream>
#include <utility>
 
struct Foo
{
    int n;
};
 
bool operator==(const Foo& lhs, const Foo& rhs)
{
    return lhs.n == rhs.n;
}
 
bool operator<(const Foo& lhs, const Foo& rhs)
{
    return lhs.n < rhs.n;
}
 
int main()
{
    Foo f1 = {1};
    Foo f2 = {2};
    using namespace std::rel_ops;
 
    std::cout << std::boolalpha
              << "{1} != {2} : " << (f1 != f2) << '\n'
              << "{1} >  {2} : " << (f1 >  f2) << '\n'
              << "{1} <= {2} : " << (f1 <= f2) << '\n'
              << "{1} >= {2} : " << (f1 >= f2) << '\n';
}