Sha256: 1ad57537cf3eedb5dd2167b9be051f28dbf8360be56b6052a0bb01af7769b29c
Contents?: true
Size: 889 Bytes
Versions: 167
Compression:
Stored size: 889 Bytes
Contents
module Luhn (checkDigit, addends, checksum, isValid, create) where
revDigits :: Integral a => a -> [a]
revDigits n = rem10 : digits
where (quot10, rem10) = n `quotRem` 10
digits | quot10 == 0 = []
| otherwise = revDigits quot10
luhnDouble :: Integral a => a -> a
luhnDouble n | n < 5 = n * 2
| otherwise = n * 2 - 9
luhnDigits :: Integral a => a -> [a]
luhnDigits = zipWith ($) (cycle [id, luhnDouble]) . revDigits
checkDigit :: Integral a => a -> a
checkDigit = head . revDigits
addends :: Integral a => a -> [a]
addends = reverse . luhnDigits
checksum :: Integral a => a -> a
checksum = (`rem` 10) . sum . luhnDigits
isValid :: Integral a => a -> Bool
isValid = (0 ==) . checksum
create :: Integral a => a -> a
create n | chk == 0 = n10
| otherwise = n10 + (10 - chk)
where n10 = n * 10
chk = checksum n10 `rem` 10
Version data entries
167 entries across 167 versions & 1 rubygems