friend bool operator==( const poisson_distribution& lhs, const poisson_distribution& rhs ); | (1) | (since C++11) |

friend bool operator!=( const poisson_distribution& lhs, const poisson_distribution& rhs ); | (2) | (since C++11) (until C++20) |

Compares two distribution objects. Two distribution objects are equal when parameter values and internal state is the same.

1) Compares two distribution objects for equality.

2) Compares two distribution objects for inequality.

These functions are not visible to ordinary unqualified or qualified lookup, and can only be found by argument-dependent lookup when `std::poisson_distribution<ResultType>`

is an associated class of the arguments.

The | (since C++20) |

lhs, rhs | - | distribution objects to compare |

1)

`true`

if the distribution objects are equal, `false`

otherwise.
2)

`true`

if the distribution objects are not equal, `false`

otherwise.Constant.

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

DR | Applied to | Behavior as published | Correct behavior |
---|---|---|---|

LWG 3519 | C++11 | the form of equality operators were unspecified (could be hidden friends or free function templates) | specified to be hidden friends |

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