operator==,!=,<,<=,>,>=(std::tuple) - cppreference.com

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# operator==,!=,<,<=,>,>=(std::tuple)

From cppreference.com
< cpp‎ | utility‎ | tuple

Defined in header `<tuple>` |  |
template< class... TTypes, class... UTypes > bool operator==( const tuple<TTypes...>& lhs, const tuple<UTypes...>& rhs ); | (1) | (since C++11) (until C++14)
template< class... TTypes, class... UTypes > constexpr bool operator==( const tuple<TTypes...>& lhs, const tuple<UTypes...>& rhs ); | (1) | (since C++14)
template< class... TTypes, class... UTypes > bool operator!=( const tuple<TTypes...>& lhs, const tuple<UTypes...>& rhs ); | (2) | (since C++11) (until C++14)
template< class... TTypes, class... UTypes > constexpr bool operator!=( const tuple<TTypes...>& lhs, const tuple<UTypes...>& rhs ); | (2) | (since C++14)
template< class... TTypes, class... UTypes > bool operator<( const tuple<TTypes...>& lhs, const tuple<UTypes...>& rhs ); | (3) | (since C++11) (until C++14)
template< class... TTypes, class... UTypes > constexpr bool operator<( const tuple<TTypes...>& lhs, const tuple<UTypes...>& rhs ); | (3) | (since C++14)
template< class... TTypes, class... UTypes > bool operator<=( const tuple<TTypes...>& lhs, const tuple<UTypes...>& rhs ); | (4) | (since C++11) (until C++14)
template< class... TTypes, class... UTypes > constexpr bool operator<=( const tuple<TTypes...>& lhs, const tuple<UTypes...>& rhs ); | (4) | (since C++14)
template< class... TTypes, class... UTypes > bool operator>( const tuple<TTypes...>& lhs, const tuple<UTypes...>& rhs ); | (5) | (since C++11) (until C++14)
template< class... TTypes, class... UTypes > constexpr bool operator>( const tuple<TTypes...>& lhs, const tuple<UTypes...>& rhs ); | (5) | (since C++14)
template< class... TTypes, class... UTypes > bool operator>=( const tuple<TTypes...>& lhs, const tuple<UTypes...>& rhs ); | (6) | (since C++11) (until C++14)
template< class... TTypes, class... UTypes > constexpr bool operator>=( const tuple<TTypes...>& lhs, const tuple<UTypes...>& rhs ); | (6) | (since C++14)

1-2) Compares every element of the tuple `lhs` with the corresponding element of the tuple `rhs`.

3-6) Compares `lhs` and `rhs` lexicographically, that is, compares the first elements, if they are equivalent, compares the second elements, if those are equivalent, compares the third elements, and so on.

All comparison operators are short-circuited; they do not access tuple elements beyond what is necessary to determine the result of the comparison.

### [edit] Parameters

lhs, rhs | - | tuples to compare

### [edit] Return value

1) true if std::get<i>(lhs) == std::get<i>(rhs) for all i in `[0, sizeof...(Types))`, otherwise false. For two empty tuples returns true.

2) !(lhs == rhs)

3) (bool)(std::get<0>(lhs) < std::get<0>(rhs)) || (!(bool)(std::get<0>(rhs) < std::get<0>(lhs)) && lhstail < rhstail), where `lhstail` is lhs without its first element, and `rhstail` is rhs without its first element. For two empty tuples, returns false.

4) !(rhs < lhs)

5) rhs < lhs

6) !(lhs < rhs)

### [edit] Example

Because operator< is defined for tuples, containers of tuples can be sorted.

Run this code

    #include <iostream>
    #include <tuple>
    #include <vector>
    #include <algorithm>
    int main()
    {
        std::vector<std::tuple<int, std::string, float>> v;
        v.emplace_back(2, "baz", -0.1);
        v.emplace_back(2, "bar", 3.14);
        v.emplace_back(1, "foo", 100.1);
        std::sort(v.begin(), v.end());

        for(auto p: v) {
            std::cout << "(" << std::get<0>(p) << ", " << std::get<1>(p)
                      << ", " << std::get<2>(p) << ")\n";
        }
    }

Output:

    (1, foo, 100.1)
    (2, bar, 3.14)
    (2, baz, -0.1)

### [edit] See also

Retrieved from "http://en.cppreference.com/mwiki/index.php?title=cpp/utility/tuple/operator_cmp&oldid=89935"