# duration Class

**Visual Studio 2015**

The latest version of this topic can be found at duration Class.

Describes a type that holds a *time interval*, which is an elapsed time between two time points.

template <class Rep, class Period = ratio<1>> class duration; template <class Rep, class Period> class duration; template <class Rep, class Period1, class Period2> class duration <duration<Rep, Period1>, Period2>;

The template argument `Rep`

describes the type that is used to hold the number of clock ticks in the interval. The template argument `Period`

is an instantiation of ratio that describes the size of the interval that each tick represents.

### Public Typedefs

Name | Description |
---|---|

duration::period Typedef | Represents a synonym for the template parameter `Period` . |

duration::rep Typedef | Represents a synonym for the template parameter `Rep` . |

### Public Constructors

Name | Description |
---|---|

duration::duration Constructor | Constructs a `duration` object. |

### Public Methods

Name | Description |
---|---|

duration::count Method | Returns the number of clock ticks in the time interval. |

duration::max Method | Static. Returns the maximum allowable value of template parameter `Ref` . |

duration::min Method | Static. Returns the lowest allowable value of template parameter `Ref` . |

duration::zero Method | Static. In effect, returns `Rep` (0). |

### Public Operators

Name | Description |
---|---|

duration::operator- | Returns a copy of the `duration` object together with a negated tick count. |

duration::operator-- | Decrements the stored tick count. |

duration::operator= | Reduces the stored tick count modulo a specified value. |

duration::operator*= | Multiplies the stored tick count by a specified value. |

duration::operator/= | Divides the stored tick count by the tick count of a specified `duration` object. |

duration::operator+ | Returns `*this` . |

duration::operator++ | Increments the stored tick count. |

duration::operator+= | Adds the tick count of a specified `duration` object to the stored tick count. |

duration::operator-= | Subtracts the tick count of a specified `duration` object from the stored tick count. |

**Header:** chrono

**Namespace:** std::chrono

Retrieves the number of clock ticks in the time interval.

constexpr Rep count() const;

### Return Value

The number of clock ticks in the time interval.

Constructs a `duration`

object.

constexpr duration() = default; template <class Rep2> constexpr explicit duration(const Rep2& R); template <class Rep2, class Period2> constexpr duration(const duration<Rep2, Period2>& Dur);

### Parameters

`Rep2`

An arithmetic type to represent the number of ticks.

`Period2`

A `std::ratio`

template specialization to represent the tick period in units of seconds.

`R`

The number of ticks of default period.

`Dur`

The number of ticks of period specified by `Period2`

.

### Remarks

The default constructor constructs an object that is uninitialized. Value initialization by using empty braces initializes an object that represents a time interval of zero clock ticks.

The second, one template argument constructor constructs an object that represents a time interval of `R`

clock ticks using a default period of `std::ratio<1>`

. To avoid round-off of tick counts, it is an error to construct a duration object from a representation type `Rep2`

that can be treated as a floating-point type when `duration::rep`

cannot be treated as a floating-point type.

The third, two template argument constructor constructs an object that represents a time interval whose length is the time interval that is specified by `Dur`

. To avoid truncation of tick counts, it is an error to construct a duration object from another duration object whose type is *incommensurable* with the target type.

A duration type `D1`

is *incommensurable* with another duration type `D2`

if `D2`

cannot be treated as a floating-point type and ratio_divide<D1::period, D2::period>::type::den is not 1.

Unless `Rep2`

is implicitly convertible to `rep`

and either `treat_as_floating_point<rep>`

*holds true* or `treat_as_floating_point<Rep2>`

*holds false*, the second constructor does not participate in overload resolution. For more information, see <type_traits>.

Unless no overflow is induced in the conversion and `treat_as_floating_point<rep>`

*holds true*, or both `ratio_divide<Period2, period>::den`

equals 1 and `treat_as_floating_point<Rep2>`

*holds false*, the third constructor does not participate in overload resolution. For more information, see <type_traits>.

Static method that returns the upper bound for values of template parameter type `Ref`

.

static constexpr duration max();

### Return Value

In effect, returns `duration(duration_values<rep>::max())`

.

Static method that returns the lower bound for values of template parameter type `Ref`

.

static constexpr duration min();

### Return Value

In effect, returns `duration(duration_values<rep>::min())`

.

Returns a copy of the `duration`

object together with a negated tick count.

constexpr duration operator-() const;

Decrements the stored tick count.

duration& operator--(); duration operator--(int);

### Return Value

The first method returns `*this`

.

The second method returns a copy of `*this`

that is made before the decrement.

Reduces the stored tick count modulo a specified value.

duration& operator%=(const rep& Div); duration& operator%=(const duration& Div);

### Parameters

`Div`

For the first method, `Div`

represents a tick count. For the second method, `Div`

is a `duration`

object that contains a tick count.

### Return Value

The `duration`

object after the modulo operation is performed.

Multiplies the stored tick count by a specified value.

duration& operator*=(const rep& Mult);

### Parameters

`Mult`

A value of the type that is specified by `duration::rep`

.

### Return Value

The `duration`

object after the multiplication is performed.

Divides the stored tick count by a specified value.

duration& operator/=(const rep& Div);

### Parameters

`Div`

A value of the type that is specified by `duration::rep`

.

### Return Value

The `duration`

object after the division is performed.

Returns `*this`

.

constexpr duration operator+() const;

Increments the stored tick count.

duration& operator++(); duration operator++(int);

### Return Value

The first method returns `*this`

.

The second method returns a copy of `*this`

that is made before the increment.

Adds the tick count of a specified `duration`

object to the stored tick count.

duration& operator+=(const duration& Dur);

### Parameters

`Dur`

A `duration`

object.

### Return Value

The `duration`

object after the addition is performed.

Subtracts the tick count of a specified `duration`

object from the stored tick count.

duration& operator-=(const duration& Dur);

### Parameters

`Dur`

A `duration`

object.

### Return Value

The `duration`

object after the subtraction is performed.

Returns `duration(duration_values<rep>::zero())`

.

static constexpr duration zero();

Reduces the stored tick count modulo Div or Div.count().

duration& operator%=(const rep& Div);duration& operator%=(const duration& Div);

### Parameters

`Div`

The divisor, which is either a duration object or a value that represents tick counts.

### Remarks

The first member function reduces the stored tick count modulo Div and returns *this. The second member function reduces the stored tick count modulo Div.count() and returns *this.