Defined in header `<type_traits>` | ||
---|---|---|

template< class T > struct has_unique_object_representations; | (since C++17) |

If `T`

is `TriviallyCopyable`

and if any two objects of type `T`

with the same value have the same object representation, provides the member constant `value`

equal `true`

. For any other type, `value`

is `false`

.

For the purpose of this trait, two arrays have the same value if their elements have the same values, two non-union classes have the same value if their direct subobjects have the same value, and two unions have the same value if they have the same active member and the value of that member are the same.

It is implementation-defined which scalar types satisfy this trait, but unsigned integer types that do not use padding bits are guaranteed to have unique object representations.

The behavior is undefined if `T`

is an incomplete type other than (possibly cv-qualified) `void`

or array of unknown bound.

T | - | a type to check |

template< class T > inline constexpr bool has_unique_object_representations_v = has_unique_object_representations<T>::value; | (since C++17) |

value
[static] | `true` if `T` has unique object representations , `false` otherwise (public static member constant) |

operator bool | converts the object to `bool` , returns `value` (public member function) |

operator()
(C++14) | returns `value` (public member function) |

Type | Definition |
---|---|

`value_type` | `bool` |

`type` | `std::integral_constant<bool, value>` |

This trait was introduced to make it possible to determine whether a type can be correctly hashed by hashing its object representation as a byte array.

(C++11) | checks if a type is standard-layout type (class template) |

(C++11) | hash function object (class template) |

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