Insertable v0.2.0 Insertable protocol View Source

Insertable is a simple protocol that allows for the insertion of ellements into a collection, one element at a time.

This is the major difference with the Collectable protocol: Collectable only works with inserting many items at a time, so inserting one item using Collectable requires wrapping it inside an enumerable first, meaning that superfluous work is done when only inserting items one by one. Furthermore, Collectable might perform extra work once the collecting has finished, which means that the resulting collection might actually be different than expected.

One important difference, for example, is that the Insertable implementation for lists naturally inserts a new item at the head side of the list. Collectable on the other hand builds a new list by first enumerating all items in the new collection, then putting the original items on top, and then reversing the result. (Thus iterating through all elements of a list every time when item(s) are inserted)

Link to this section Summary

Types

t()

Functions

insert(insertable, item)

Insertable.insert/2 returns {:ok, collection} where collection is the new collection with the item having been inserted (possibly replacing an already-existing item in the process), or {:error, reason} if it is impossible to insert the item for some reason

Link to this section Types

t()

t() :: term

Link to this section Functions

insert(insertable, item)

insert(Insertable.t, item :: any) ::
  {:ok, Insertable.t} |
  {:error, :invalid_item_type} |
  {:error, :full} |
  {:error, other_reason :: any}

The following error reasons are standardized, allowing the caller to handle them gracefully:

:invalid_item_type: To be returned if the item cannot be inserted because it is incompatible with the stuff already inside the collection. Examples of this would be Maps, for which only {key, value}-items make sense, or for instance matrices, for which only vectors of the same size as the matrix’ height make sense.
:full: To be returned if the collection only allows a limited number of items, and one first should be removed again after another item can be inserted.

Examples

iex> Insertable.insert([], 1)
{:ok, [1]}

iex> Insertable.insert([1, 2, 3, 4], 5)
{:ok, [5, 1, 2, 3, 4]}

iex> Insertable.insert(%{a: 10, b: 20}, {:a, 30})
{:ok, %{a: 30, b: 20}}

iex> Insertable.insert(%{a: 1, b: 2}, 42)
{:error, :invalid_item_type}

iex> {:ok, result} = Insertable.insert(MapSet.new([1, 2, 3, 4]), 33)
iex> result
#MapSet<[1, 2, 3, 4, 33]>