exercism/elixir/strain/lib/strain.ex

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Elixir
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2024-03-10 12:53:48 +00:00
defmodule Strain do
@doc """
Given a `list` of items and a function `fun`, return the list of items where
`fun` returns true.
Do not use `Enum.filter`.
"""
@spec keep(list :: list(any), fun :: (any -> boolean)) :: list(any)
def keep([], _fun), do: []
def keep([head | tail], fun) do
if fun.(head), do: [head | keep(tail, fun)], else: keep(tail, fun)
end
@doc """
Given a `list` of items and a function `fun`, return the list of items where
`fun` returns false.
Do not use `Enum.reject`.
"""
@spec discard(list :: list(any), fun :: (any -> boolean)) :: list(any)
def discard(list, fun), do: keep(list, &!fun.(&1))
end