exercism/elixir/all-your-base/lib/all_your_base.ex

32 lines
1.1 KiB
Elixir

defmodule AllYourBase do
@doc """
Given a number in input base, represented as a sequence of digits, converts it to output base,
or returns an error tuple if either of the bases are less than 2
"""
@spec convert(list, integer, integer) :: {:ok, list} | {:error, String.t()}
def convert(_digits, input_base, _output_base) when input_base < 2,
do: {:error, "input base must be >= 2"}
def convert(_digits, _input_base, output_base) when output_base < 2,
do: {:error, "output base must be >= 2"}
def convert([0 | digits], input_base, output_base), do: convert(digits, input_base, output_base)
def convert(digits, input_base, output_base) do
unless Enum.all?(digits, &valid_digit?(&1, input_base)) do
{:error, "all digits must be >= 0 and < input base"}
else
result =
digits
|> Integer.undigits(input_base)
|> Integer.digits(output_base)
{:ok, result}
end
end
defp valid_digit?(digit, base) when digit >= 0 and digit < base, do: true
defp valid_digit?(_digit, _base), do: false
end