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Contents
defmodule AllYourBase do
@doc """
Given a number in base a, represented as a sequence of digits, converts it to base b,
or returns nil if either of the bases are less than 2
"""
@spec convert(list, integer, integer) :: list
def convert(digits, base_a, base_b) do
cond do
base_a > 1 and base_b > 1 and digits != [] ->
do_convert(digits, base_a, base_b)
true ->
nil
end
end
defp do_convert(digits, base_a, base_b) do
num = convert_to_num(digits, base_a, 0)
case num do
nil ->
nil
0 ->
[0]
num ->
convert_to_digits(num, base_b, [])
|> Enum.reverse()
end
end
defp convert_to_num([head | tail], base_a, accumulator) do
cond do
head < base_a and head >= 0 ->
convert_to_num(tail, base_a, accumulator * base_a + head)
true ->
nil
end
end
defp convert_to_num([], _base_a, accumulator) do
accumulator
end
defp convert_to_digits(num, base_b, arr) when num > 0 do
convert_to_digits(div(num, base_b), base_b, arr ++ [rem(num, base_b)])
end
defp convert_to_digits(num, _base_b, arr) when num == 0 do
arr
end
end
Version data entries
69 entries across 69 versions & 1 rubygems