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

C++

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Technical Specifications

Utilities library

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Relational operators (deprecated)
rel_ops::operator!=rel_ops::operator>rel_ops::operator<=rel_ops::operator>=
Comparisons (C++20)
strong_order weak_order partial_order strong_equal weak_equal	strong_ordering weak_ordering partial_ordering strong_equality weak_equality	is_eqis_neqis_ltis_lteqis_gtis_gteq
common_comparison_category
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pair tuple (C++11) apply (C++17) make_from_tuple (C++17)	optional (C++17) any (C++17) variant (C++17)
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swap
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std::tuple

Member functions

tuple::tuple

tuple::operator=

tuple::swap

Non-member functions

make_tuple

tie

forward_as_tuple

tuple_cat

operator==operator!=operator<operator<=operator>operator>=

std::swap

get

Deduction guides(C++17)

Helper classes

tuple_size

tuple_element

uses_allocator

ignore

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

Parameters

lhs, rhs

-

tuples to compare

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)

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)