Sha256: 45aa47d2e6a7091279df07ec240a98c78d2bd085374940aac3dcd46a109c5595
Contents?: true
Size: 808 Bytes
Versions: 63
Compression:
Stored size: 808 Bytes
Contents
defmodule Luhn do
@doc """
Checks if the given number is valid via the luhn formula
"""
@spec valid?(String.t()) :: boolean
def valid?(number) do
number_without_spaces = String.replace(number, " ", "")
case Integer.parse(number_without_spaces) do
{_, ""} ->
String.length(number_without_spaces) > 1 && checksum(number_without_spaces)
_ ->
false
end
end
defp checksum(number) do
0 == number
|> String.graphemes()
|> Enum.map(&String.to_integer/1)
|> double_even()
|> Enum.sum()
|> rem(10)
end
defp double_even(numlist) do
numlist
|> Enum.reverse()
|> Enum.zip(Stream.cycle([1,2]))
|> Enum.map(fn {n,m} -> n * m end)
|> Enum.map(
fn
n when n > 9 -> n-9
n -> n
end)
end
end
Version data entries
63 entries across 63 versions & 1 rubygems