View Source Credo.Check.Refactor.RejectFilter (Credo v1.7.5)


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This check is tagged :controversial

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This check has a base priority of 0 and works with any version of Elixir.


One Enum.filter/2 is more efficient than Enum.reject/2 |> Enum.filter/2.

This should be refactored:

["a", "b", "c"]
|> Enum.reject(&String.contains?(&1, "x"))
|> Enum.filter(&String.contains?(&1, "a"))

to look like this:

Enum.filter(["a", "b", "c"], fn letter ->
  !String.contains?(letter, "x") && String.contains?(letter, "a")

The reason for this is performance, because the two calls to Enum.reject/2 and Enum.filter/2 require two iterations whereas doing the functions in the single Enum.filter/2 only requires one.

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