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linked_list.ex
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linked_list.ex
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defmodule ExAlgo.List.LinkedList do
@moduledoc """
Implementation of a singly linked list.
"""
@type neg_index_error :: {:error, :negative_index}
@type empty_error :: {:error, :empty_list}
@type value_type :: any()
@type t :: %__MODULE__{container: [value_type()]}
defstruct container: []
@doc """
Creates an empty linked list.
## Example
iex> LinkedList.new
%LinkedList{container: []}
"""
@spec new :: t()
def new, do: %__MODULE__{container: []}
@doc """
Creates an empty linked list from a list
## Example
iex> LinkedList.from 1..3
%LinkedList{container: [1, 2, 3]}
"""
@spec from(Enumerable.t()) :: t()
def from(enumerable), do: %__MODULE__{container: Enum.to_list(enumerable)}
@doc """
Inserts a new element on the head of the list.
## Example
iex> list = LinkedList.from 1..3
iex> list |> LinkedList.insert(10)
%LinkedList{container: [10, 1, 2, 3]}
"""
@spec insert(t(), value_type()) :: t()
def insert(%__MODULE__{container: container}, element),
do: %__MODULE__{container: [element | container]}
@doc """
Removes the head.
## Example
iex> list = LinkedList.from 1..3
iex> list |> LinkedList.remove()
{1, %LinkedList{container: [2, 3]}}
iex> LinkedList.new() |> LinkedList.remove()
{:error, :empty_list}
"""
@spec remove(t()) :: {value_type(), t()} | empty_error()
def remove(%__MODULE__{container: []}), do: {:error, :empty_list}
def remove(%__MODULE__{container: [head | rest]}), do: {head, %__MODULE__{container: rest}}
@doc """
Returns the head of the linked list
## Example
iex> LinkedList.from(1..10) |> LinkedList.head()
1
iex> LinkedList.new |> LinkedList.head()
{:error, :empty_list}
"""
@spec head(t()) :: empty_error()
def head(%__MODULE__{container: [head | _]}), do: head
def head(_), do: {:error, :empty_list}
@doc """
Returns the next items of the linked list
## Example
iex> LinkedList.from(1..3) |> LinkedList.next()
%LinkedList{container: [2, 3]}
iex> LinkedList.new |> LinkedList.next()
{:error, :empty_list}
"""
@spec next(t()) :: t() | empty_error()
def next(%__MODULE__{container: [_ | next]}), do: %__MODULE__{container: next}
def next(_), do: {:error, :empty_list}
@doc """
Return the element at index. Index is 0 based and must be positive. Errors on empty list.
## Example
iex> LinkedList.from(0..10) |> LinkedList.at(3)
3
"""
@spec at(t(), value_type()) :: value_type() | empty_error() | neg_index_error()
def at(%__MODULE__{container: []}, _), do: {:error, :empty_list}
def at(_, index) when index < 0, do: {:error, :negative_index}
def at(list, 0), do: list |> head()
def at(list, index), do: list |> next() |> at(index - 1)
end