# 
[](https://github.com/tbug/elixir_interval/actions/workflows/ci.yml)
[](https://hex.pm/packages/interval)
[](https://hexdocs.pm/interval/)
Datatype and operations for both discrete and continuous intervals,
Inspired by [PostgreSQL's range types](https://www.postgresql.org/docs/current/rangetypes.html).
Find the documentation at https://hexdocs.pm/interval/
## Installation
The package can be installed by adding `interval` to your list of dependencies in `mix.exs`:
```elixir
def deps do
[
{:interval, "~> 0.3.4"}
]
end
```
## Built-in Interval Types
- `Interval.Integer` A discrete interval between two integers.
- `Interval.Float` A continuous interval between two floats.
- `Interval.Decimal` A continuous interval between two `Decimal` structs.
- `Interval.Date` A discrete interval between two `Date` structs.
- `Interval.DateTime` A continuous interval between two `DateTime` structs.
- `Interval.NaiveDateTime` A continuous interval between two `NaiveDateTime` structs.
## Ecto & Postgres `range` types
The builtin types (Like `Interval.DateTime`) can be used as an `Ecto.Type` out
of the box:
```elixir
# ...
schema "reservations" do
field :period, Interval.DateTime
# ...
end
# ...
```
Note though, that this feature only works with `Postgrex`, as the
intervals are converted to a `Postgrex.Range` struct which maps to the correct
range type in the database (like `tstzrange` etc.)
## Defining your own interval type
The library contains a `use` macro that does most of the work for you.
You must implement the `Interval.Behaviour`, which contains a handful of functions.
This is the full definition of the built-in `Interval.Decimal`:
```elixir
defmodule Interval.Decimal do
use Interval, type: Decimal, discrete: false
if Interval.Support.EctoType.supported?() do
use Interval.Support.EctoType, ecto_type: :numrange
end
@spec size(t()) :: Decimal.t() | nil
def size(%__MODULE__{left: {_, a}, right: {_, b}}), do: Decimal.sub(b, a)
def size(%__MODULE__{left: :empty, right: :empty}), do: Decimal.new(0)
def size(%__MODULE__{left: :unbounded}), do: nil
def size(%__MODULE__{right: :unbounded}), do: nil
@spec point_valid?(Decimal.t()) :: boolean()
def point_valid?(a), do: is_struct(a, Decimal)
@spec point_compare(Decimal.t(), Decimal.t()) :: :lt | :eq | :gt
def point_compare(a, b) when is_struct(a, Decimal) and is_struct(b, Decimal) do
Decimal.compare(a, b)
end
@spec point_step(Decimal.t(), any()) :: nil
def point_step(a, _n) when is_struct(a, Decimal), do: nil
end
```
As you can see, defining your own interval types is pretty easy.
## More Examples
### Integer intervals
Integer intervals are discrete intervals (just like the `int4range` in postgres).
```elixir
a = Interval.Integer.new(left: 1, right: 4, bounds: "[]")
b = Interval.Integer.new(left: 2, right: 5, bounds: "[]")
assert Interval.contains?(a, b)
assert Interval.overlaps?(a, b)
c = Interval.intersection(a, b) # [2, 4]
d = Interval.union(a, b) # [1, 5]
```
Discrete intervals are always normalized to the bound form `[)` (just like in postgres).
### DateTime intervals
DateTime intervals are continuous intervals (just like `tstzrange` in postgrex).
```elixir
# default bound is "[)"
y2022 = Interval.DateTime.new(left: ~U[2022-01-01 00:00:00Z], right: ~U[2023-01-01 00:00:00Z])
x = Interval.DateTime.new(left: ~U[2018-07-01 00:00:00Z], right: ~U[2022-03-01 00:00:00Z])
Interval.intersection(y2022, x)
# %Interval.DateTime{
# left: {:inclusive, ~U[2022-01-01 00:00:00Z]},
# right: {:exclusive, ~U[2022-03-01 00:00:00Z]}
# }
```
