some work towards big multiplication

EulerMath/BigNum.hs

@@ -12,14 +12,23 @@ type BigNat = [Int]
 
 bigSum :: [BigNat] -> BigNat
 bigSum = carry . map sum . transpose
-	where
-		carry (n:m:ms) = mod n 10 : carry ((m + quot n 10) : ms)
-		carry (0:[]) = []
-		carry (n:[]) = carry [n,0]
+
+carry :: BigNat -> BigNat
+carry (n:m:ms) = mod n 10 : carry ((m + quot n 10) : ms)
+carry (0:[]) = []
+carry (n:[]) = carry [n,0]
 
 stringToBigNat :: String -> BigNat
 stringToBigNat = reverse . map digitToInt
 
 bigNatToString :: BigNat -> [Char]
 bigNatToString = map intToDigit . reverse
 
+shift :: Int -> BigNat-> BigNat
+shift n = (++) $ replicate n 0 
+
+timesDigit :: (Int, Int) -> BigNat -> BigNat
+timesDigit (value, place) = carry . shift place . map (*value)
+
+withPlace :: BigNat -> [(Int, Int)]
+withPlace big = zip big [0..]