--
-- addition of very long integers
--
 
import Data.Char
import Data.String
 
addRev [] [] 0 = []
addRev la [] c = addRev la [0] c
addRev [] lb c = addRev [0] lb c
addRev (a:la) (b:lb) c = q : (addRev la lb p) where (p,q) = divMod (a+b+c) 10
 
add la lb = reverse (addRev (reverse la) (reverse lb) 0)
 
stringToDigits s = map digitToInt s
digitsToString l = map intToDigit l
intToDigits n = map digitToInt (show n)
digitsToInt :: [Int] -> Integer
digitsToInt s = read (digitsToString s)
 
verifyAdd m n = ((digitsToInt (add (intToDigits m) (intToDigits n))) - (m+n)) == 0
 
main = do print (digitsToString (add (stringToDigits "67544539703981792301876431982341329878656543656") (stringToDigits "923409765450275928347539864398234659")))
          print (all (id) [verifyAdd x y | x <- [12000..13000], y <- [7500..8500]])

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