Return the interval duration, given a unit.

When the unit is one of :secs, :mins, :hours, :days, :weeks, :months, :years, the result is an integer.

When the unit is :timestamp, the result is a tuple representing a valid Timex.Time.

Example

iex> use Timex ...> Interval.new(from: Date.from({2014, 9, 22}), until: [months: 5]) ...> |> Interval.duration(:months) 5

iex> use Timex ...> Interval.new(from: Date.from({{2014, 9, 22}, {15, 30, 0}}), until: [mins: 20]) ...> |> Interval.duration(:timestamp) {0, 1200, 0}

Formats the interval as a human readable string.

Examples

iex> use Timex
...> Interval.new(from: Date.from({2014, 9, 22}), until: [days: 3])
...> |> Interval.format!("%Y-%m-%d %H:%M", :strftime)
"[2014-09-22 00:00, 2014-09-25 00:00)"

iex> use Timex
...> Interval.new(from: Date.from({2014, 9, 22}), until: [days: 3])
...> |> Interval.format!("%Y-%m-%d", :strftime)
"[2014-09-22, 2014-09-25)"

Same as format/3, but raises a Timex.Interval.FormatError on failure.

Create a new Interval struct.

Note: By default intervals are right open.

Valid keywords: - from: The date the interval starts at. Should be a DateTime. - until: Either a DateTime, or a time shift that will be applied to the from date. - left_open: Whether the interval is left open. See explanation below. - right_open: Whether the interval is right open. See explanation below. - step: The step to use when iterating the interval, defaults to [days: 1]

The termsleft_open and right_open come from the mathematical concept of intervals, the following excerpt from Wikipedia gives a good explanation of their meaning:

"An interval is said to be left-open if and only if it has no minimum
(an element that is smaller than all other elements); right-open if it has no maximum;
and open if it has both properties. The interval [0,1) = {x | 0 ≤ x < 1}, for example,
is left-closed and right-open. The empty set and the set of all reals are open intervals,
while the set of non-negative reals, for example, is a right-open but not left-open interval.
The open intervals coincide with the open sets of the real line in its standard topology."

Note: until shifts delegate to Date.shift, so the options provided should match it's valid options.

Examples

iex> use Timex ...> Interval.new(from: Date.from({2014, 9, 22}), until: Date.from({2014, 9, 29})) ...> |> Interval.format!("%Y-%m-%d", :strftime) "[2014-09-22, 2014-09-29)"

iex> use Timex ...> Interval.new(from: Date.from({2014, 9, 22}), until: [days: 7]) ...> |> Interval.format!("%Y-%m-%d", :strftime) "[2014-09-22, 2014-09-29)"

iex> use Timex ...> Interval.new(from: Date.from({2014, 9, 22}), until: [days: 7], left_open: true, right_open: false) ...> |> Interval.format!("%Y-%m-%d", :strftime) "(2014-09-22, 2014-09-29]"

iex> use Timex ...> Interval.new(from: Date.from({{2014, 9, 22}, {15, 30, 0}}), until: [mins: 20], right_open: false) ...> |> Interval.format!("%H:%M", :strftime) "[15:30, 15:50]"

Change the step value for the provided interval.

The step should be a keyword list valid for use with Timex.Date.shift.

Examples

iex> use Timex ...> Interval.new(from: Date.from({2014, 9, 22}), until: [days: 3], right_open: false) ...> |> Interval.with_step([days: 1]) |> Enum.map(&DateFormat.format!(&1, "%Y-%m-%d", :strftime)) ["2014-09-22", "2014-09-23", "2014-09-24", "2014-09-25"]

iex> use Timex ...> Interval.new(from: Date.from({2014, 9, 22}), until: [days: 3], right_open: false) ...> |> Interval.with_step([days: 2]) |> Enum.map(&DateFormat.format!(&1, "%Y-%m-%d", :strftime)) ["2014-09-22", "2014-09-24"]

iex> use Timex ...> Interval.new(from: Date.from({2014, 9, 22}), until: [days: 3], right_open: false) ...> |> Interval.with_step([days: 3]) |> Enum.map(&DateFormat.format!(&1, "%Y-%m-%d", :strftime)) ["2014-09-22", "2014-09-25"]