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[Sync Iteration] elixir/rotational-cipher/2 #12

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[Sync Iteration] elixir/rotational-cipher/2 #12

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18 changes: 18 additions & 0 deletions solutions/elixir/rotational-cipher/2/lib/rotational_cipher.ex
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Original file line number Diff line number Diff line change
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defmodule RotationalCipher do
@doc """
Given a plaintext and amount to shift by, return a rotated string.

Example:
iex> RotationalCipher.rotate("Attack at dawn", 13)
"Nggnpx ng qnja"
"""
@spec rotate(text :: String.t(), shift :: integer) :: String.t()
def rotate(text, shift) do
shift_char = fn
char when char in ?A..?Z -> <<?A + rem(char - ?A + shift, 26)>>
char when char in ?a..?z -> <<?a + rem(char - ?a + shift, 26)>>
char -> <<char>>
end
text |> String.to_charlist() |> Enum.map_join(shift_char)
end
end