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

 

C++

Language

Concepts

Utilities library

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Algorithms library

Iterators library

Numerics library

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Regular expressions library (C++11)

Atomic operations library (C++11)

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Utilities library

Type support (basic types, RTTI, type traits)

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initializer_list (C++11)

bitset

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Relational operators

rel_ops::operator!= rel_ops::operator> rel_ops::operator<= rel_ops::operator>=

Pairs and tuples

pair

tuple (C++11)

piecewise_construct_t (C++11)

piecewise_construct (C++11)

Swap, forward and move

swap

forward (C++11)

move (C++11)

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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

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

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) !(lhs < rhs)

5) rhs < lhs

6) !(rhs < lhs)

Example

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

#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)