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

From cppreference.com
< cpp‎ | container‎ | stack

template< class T, class Container > bool operator==( const std::stack<T, Container>& lhs, const std::stack<T, Container>& rhs ); | (1) |
template< class T, class Container > bool operator!=( const std::stack<T, Container>& lhs, const std::stack<T, Container>& rhs ); | (2) |
template< class T, class Container > bool operator< ( const std::stack<T, Container>& lhs, const std::stack<T, Container>& rhs ); | (3) |
template< class T, class Container > bool operator<=( const std::stack<T, Container>& lhs, const std::stack<T, Container>& rhs ); | (4) |
template< class T, class Container > bool operator> ( const std::stack<T, Container>& lhs, const std::stack<T, Container>& rhs ); | (5) |
template< class T, class Container > bool operator>=( const std::stack<T, Container>& lhs, const std::stack<T, Container>& rhs ); | (6) |
template< class T, std::three_way_comparable Container > std::compare_three_way_result_t<Container> operator<=>( const std::stack<T, Container>& lhs, const std::stack<T, Container>& rhs ); | (7) | (since C++20)

Compares the contents of the underlying containers of two container adaptors. The comparison is done by applying the corresponding operator to the underlying containers.

### Parameters

lhs, rhs | - | container adaptors whose contents to compare
- `T` must meet the requirements of EqualityComparable.

### Return value

1-6) true if the corresponding comparison yields true, false otherwise.
7) Result of three-way comparison on underlying containers.

### Complexity

Linear in the size of the container.

### Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR | Applied to | Behavior as published | Correct behavior
--- | --- | --- | ---
LWG 410 | C++98 | the semantics of all comparison operators were missing | added

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/container/stack/operator_cmp&oldid=50670"