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

 

C++

Language

Standard Library Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms 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
Library feature-test macros
Date and time
Function objects
initializer_list (C++11)
bitset
hash (C++11)
integer_sequence (C++14)
Relational operators (deprecated in C++20)
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
Common vocabulary types
pair tuple (C++11) apply (C++17) make_from_tuple (C++17)	optional (C++17) any (C++17) variant (C++17)
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)
launder (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

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)