Sha256: 12f2dc476742a5f48e90060c9db11285162128a03ae5604788eaa20da8a9bb72
Contents?: true
Size: 814 Bytes
Versions: 69
Compression:
Stored size: 814 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
69 entries across 69 versions & 1 rubygems