std::rel_ops:: operator!=,>,<=,>=
From cppreference.com
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Defined in header
<utility>
|
||
|
template
<
class
T
>
bool operator ! = ( const T & lhs, const T & rhs ) ; |
(1) | (deprecated in C++20) |
|
template
<
class
T
>
bool operator > ( const T & lhs, const T & rhs ) ; |
(2) | (deprecated in C++20) |
|
template
<
class
T
>
bool operator <= ( const T & lhs, const T & rhs ) ; |
(3) | (deprecated in C++20) |
|
template
<
class
T
>
bool operator >= ( const T & lhs, const T & rhs ) ; |
(4) | (deprecated in C++20) |
Given a user-defined
operator
==
and
operator
<
for objects of type
T
, implements the usual semantics of other comparison operators.
1)
Implements
operator
!
=
in terms of
operator
==
.
2)
Implements
operator
>
in terms of
operator
<
.
3)
Implements
operator
<=
in terms of
operator
<
.
4)
Implements
operator
>=
in terms of
operator
<
.
Parameters
| lhs | - | left-hand argument |
| rhs | - | right-hand argument |
Return value
1)
Returns
true
if
lhs
is
not equal
to
rhs
.
2)
Returns
true
if
lhs
is
greater
than
rhs
.
3)
Returns
true
if
lhs
is
less or equal
to
rhs
.
4)
Returns
true
if
lhs
is
greater or equal
to
rhs
.
Possible implementation
(1)
operator!=
|
|---|
namespace rel_ops { template<class T> bool operator!=(const T& lhs, const T& rhs) { return !(lhs == rhs); } } |
(2)
operator>
|
namespace rel_ops { template<class T> bool operator>(const T& lhs, const T& rhs) { return rhs < lhs; } } |
(3)
operator<=
|
namespace rel_ops { template<class T> bool operator<=(const T& lhs, const T& rhs) { return !(rhs < lhs); } } |
(4)
operator>=
|
namespace rel_ops { template<class T> bool operator>=(const T& lhs, const T& rhs) { return !(lhs < rhs); } } |
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
Run this code
#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'; }
Output:
{1} != {2} : true
{1} > {2} : false
{1} <= {2} : true
{1} >= {2} : false