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

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

 

Utilities library

Type support (basic types, RTTI, type traits)

Dynamic memory management

Error handling

Program utilities

Variadic functions

Date and time

Function objects

initializer_list (C++11)

bitset

hash (C++11)

Relational operators

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

optional, any and variant (C++17)

optional

any

variant

in_placein_place_typein_place_indexin_place_tin_place_type_tin_place_index_t

Pairs and tuples

pair

tuple (C++11)

apply (C++17)

make_from_tuple (C++17)

piecewise_construct_t (C++11)

piecewise_construct (C++11)

integer_sequence (C++14)

Swap, forward and move

swap

exchange (C++14)

forward (C++11)

move (C++11)

move_if_noexcept (C++11)

Elementary string conversions

to_chars (C++17)

from_chars (C++17)

chars_format (C++17)

Type operations

declval (C++11)

as_const (C++17)

 

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) (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.

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)