Elixir:使用整数键将列表转换为地图

你如何从列表中走出来: ~w[dog cat sheep]

到具有整数键的地图: %{1=> "dog", 2=> "cat", 3=> "sheep"}

我的尝试:

iex(1)> list = ~w[dog cat sheep]
["dog", "cat", "sheep"]
iex(2)> list |> Enum.with_index|>Enum.map(fn({a,b})->{b+1,a} end)|> Enum.into %{}

%{1=> "dog", 2=> "cat", 3=> "sheep"}

有更简单的方法吗？

这是一个单行版本:

for {v, k} <- ~w[dog cat sheep] |> Enum.with_index, into: %{}, do: {k+1, v}

defmodule Example do
  def to_indexed_map(list, offset \\ 0)
      when is_list(list)
      and is_integer(offset),
    do: for {v, k} <- list |> Enum.with_index,
      into: %{},
      do: {k+offset, v}
end

iex> list = ~w[dog cat sheep]
["dog", "cat", "sheep"]
iex> Example.to_indexed_map(list)
%{0 => "dog", 1 => "cat", 2 => "sheep"}

defmodule Example do
  def to_indexed_map(list, offset \\ 0)
      when is_list(list)
      and is_integer(offset),
    do: to_indexed_map(list, offset, [])

  defp to_indexed_map([], _k, acc),
    do: :maps.from_list(acc)
  defp to_indexed_map([v | vs], k, acc),
    do: to_indexed_map(vs, k+1, [{k, v} | acc])
end