# View Source Interval.Behaviour behaviour (Interval v0.3.4)

Defines the Interval behaviour. You'll usually want to use this behaviour by using

`use Interval, type: MyType`

In your own interval modules, instead of defining the behaviour directly.

# Link to this section Summary

## Callbacks

Is this implementation of an interval considered discrete?

Create a new `Interval.t/0`

Compare two points, returning if `a == b`

, `a > b`

or `a < b`

.

Step a discrete point `n`

steps.

Is the given argument a valid point in this Interval implementation.

Return the "size" of the interval. The returned value depends on the interval implementation used.

# Link to this section Types

@type new_opt() :: {:left, Interval.point()} | {:right, Interval.point()} | {:bounds, String.t()}

@type new_opts() :: [new_opt()]

# Link to this section Callbacks

@callback discrete?() :: boolean()

Is this implementation of an interval considered discrete?

The interval is implicitly continuous if not discrete.

@callback new(new_opts()) :: Interval.t()

Create a new `Interval.t/0`

@callback point_compare(Interval.point(), Interval.point()) :: :eq | :gt | :lt

Compare two points, returning if `a == b`

, `a > b`

or `a < b`

.

@callback point_step(Interval.point(), n :: integer()) :: Interval.point()

Step a discrete point `n`

steps.

If `n`

is negative, the point is stepped backwards.
For integers this is simply addition (`point + n`

)

@callback point_valid?(Interval.point()) :: boolean()

Is the given argument a valid point in this Interval implementation.

@callback size(Interval.t()) :: any()

Return the "size" of the interval. The returned value depends on the interval implementation used.

##
for-discrete-intervals

For Discrete Intervals

For discrete point types, the size represents the number of elements the interval contains.

I.e. for `Date`

the size is the number of `Date`

structs the interval
can be said to "contain" (the number of days)

###
examples

Examples

```
iex> size(new(module: Interval.Integer, left: 1, right: 1, bounds: "[]"))
1
iex> size(new(module: Interval.Integer, left: 1, right: 3, bounds: "[)"))
2
# Note that this interval will be normalized to an empty interval
# due to the bounds:
iex> size(new(module: Interval.Integer, left: 1, right: 2, bounds: "()"))
0
```

##
for-continuous-intervals

For Continuous Intervals

For continuous intervals, the size is reported as the difference between the left and right points.

###
examples-1

Examples

```
# The size of the interval `[1.0, 5.0)` is also 4:
iex> size(new(module: Interval.Float, left: 1.0, right: 5.0, bounds: "[)"))
4.0
# And likewise, so is the size of `[1.0, 5.0]` (note the bound change)
iex> size(new(module: Interval.Float, left: 1.0, right: 5.0, bounds: "[]"))
4.0
# Exactly one point contained in this continuous interval,
# so technically not empty, but it also has zero size.
iex> size(new(module: Interval.Float, left: 1.0, right: 1.0, bounds: "[]"))
0.0
# Empty continuous interval
iex> size(new(module: Interval.Float, left: 1.0, right: 1.0, bounds: "()"))
0.0
```