operator==,!=,<,<=,>,>=(std::pair)
Defined in header <utility>
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template< class T1, class T2 > bool operator==( const pair<T1,T2>& lhs, const pair<T1,T2>& rhs ); |
(1) | (until C++14) |
template< class T1, class T2 > constexpr bool operator==( const pair<T1,T2>& lhs, const pair<T1,T2>& rhs ); |
(1) | (since C++14) |
template< class T1, class T2 > bool operator!=( const pair<T1,T2>& lhs, const pair<T1,T2>& rhs ); |
(2) | (until C++14) |
template< class T1, class T2 > constexpr bool operator!=( const pair<T1,T2>& lhs, const pair<T1,T2>& rhs ); |
(2) | (since C++14) |
template< class T1, class T2 > bool operator<( const pair<T1,T2>& lhs, const pair<T1,T2>& rhs ); |
(3) | (until C++14) |
template< class T1, class T2 > constexpr bool operator<( const pair<T1,T2>& lhs, const pair<T1,T2>& rhs ); |
(3) | (since C++14) |
template< class T1, class T2 > bool operator<=( const pair<T1,T2>& lhs, const pair<T1,T2>& rhs ); |
(4) | (until C++14) |
template< class T1, class T2 > constexpr bool operator<=( const pair<T1,T2>& lhs, const pair<T1,T2>& rhs ); |
(4) | (since C++14) |
template< class T1, class T2 > bool operator>( const pair<T1,T2>& lhs, const pair<T1,T2>& rhs ); |
(5) | (until C++14) |
template< class T1, class T2 > constexpr bool operator>( const pair<T1,T2>& lhs, const pair<T1,T2>& rhs ); |
(5) | (since C++14) |
template< class T1, class T2 > bool operator>=( const pair<T1,T2>& lhs, const pair<T1,T2>& rhs ); |
(6) | (until C++14) |
template< class T1, class T2 > constexpr bool operator>=( const pair<T1,T2>& lhs, const pair<T1,T2>& rhs ); |
(6) | (since C++14) |
1-2) Tests if both elements of lhs and rhs are equal, that is, compares
lhs.first
with rhs.first
and lhs.second
with rhs.second
3-6) Compares
lhs
and rhs
lexicographically, that is, compares the first elements and only if they are equivalent, compares the second elements.Parameters
lhs, rhs | - | pairs to compare |
Return value
1) true if both lhs.first == rhs.first
and lhs.second == rhs.second
, otherwise false
2) !(lhs == rhs)
3) If lhs.first<rhs.first
, returns true. Otherwise, if rhs.first<lhs.first
, returns false. Otherwise, if lhs.second<rhs.second
, returns true. Otherwise, returns false.
4) !(rhs < lhs)
5) rhs < lhs
6) !(lhs < rhs)
Example
Because operator< is defined for pairs, containers of pairs can be sorted.
Run this code
#include <iostream> #include <utility> #include <vector> #include <algorithm> #include <string> int main() { std::vector<std::pair<int, std::string>> v = { {2, "baz"}, {2, "bar"}, {1, "foo"} }; std::sort(v.begin(), v.end()); for(auto p: v) { std::cout << "(" << p.first << "," << p.second << ")\n"; } }
Output:
(1,foo) (2,bar) (2,baz)