hw1: init

hw1/BigNum.hs

@@ -0,0 +1,89 @@
+{-
+  Name: <Your name here>
+  Class: CS 252
+  Assigment: HW1
+  Date: <Date assignment is due>
+  Description: <Describe the program and what it does>
+-}
+
+module BigNum (
+  BigNum,
+  bigAdd,
+  bigSubtract,
+  bigMultiply,
+  bigEq,
+  bigDec,
+  bigPowerOf,
+  prettyPrint,
+  stringToBigNum,
+) where
+
+type Block = Int -- An Int from 0-999
+
+type BigNum = [Block]
+
+maxblock = 1000
+
+bigAdd :: BigNum -> BigNum -> BigNum
+bigAdd x y = bigAdd' x y 0
+
+bigAdd' :: BigNum -> BigNum -> Block -> BigNum
+bigAdd' _ _ _ = error "Your code here"
+
+bigSubtract :: BigNum -> BigNum -> BigNum
+bigSubtract x y =
+  if length x < length y
+    then error "Negative numbers not supported"
+    else reverse $ stripLeadingZeroes $ reverse result
+      where result = bigSubtract' x y 0
+
+stripLeadingZeroes :: BigNum -> BigNum
+stripLeadingZeroes (0:[]) = [0]
+stripLeadingZeroes (0:xs) = stripLeadingZeroes xs
+stripLeadingZeroes xs = xs
+
+-- Negative numbers are not supported, so you may throw an error in these cases
+bigSubtract' :: BigNum -> BigNum -> Block -> BigNum
+bigSubtract' _ _ _ = error "Your code here"
+
+bigEq :: BigNum -> BigNum -> Bool
+bigEq _ _ = error "Your code here"
+
+bigDec :: BigNum -> BigNum
+bigDec x = bigSubtract x [1]
+
+-- Handle multiplication following the same approach you learned in grade
+-- school, except dealing with blocks of 3 digits rather than single digits.
+-- If you are having trouble finding a solution, write a helper method that
+-- multiplies a BigNum by an Int.
+bigMultiply :: BigNum -> BigNum -> BigNum
+bigMultiply _ _ = error "Your code here"
+
+bigPowerOf :: BigNum -> BigNum -> BigNum
+bigPowerOf _ _ = error "Your code here"
+
+prettyPrint :: BigNum -> String
+prettyPrint [] = ""
+prettyPrint xs = show first ++ prettyPrint' rest
+  where (first:rest) = reverse xs
+
+prettyPrint' :: BigNum -> String
+prettyPrint' [] = ""
+prettyPrint' (x:xs) = prettyPrintBlock x ++ prettyPrint' xs
+
+prettyPrintBlock :: Int -> String
+prettyPrintBlock x | x < 10     = ",00" ++ show x
+                   | x < 100    = ",0" ++ show x
+                   | otherwise  = "," ++ show x
+
+stringToBigNum :: String -> BigNum
+stringToBigNum "0" = [0]
+stringToBigNum s = stringToBigNum' $ reverse s
+
+stringToBigNum' :: String -> BigNum
+stringToBigNum' [] = []
+stringToBigNum' s | length s <= 3 = read (reverse s) : []
+stringToBigNum' (a:b:c:rest) = block : stringToBigNum' rest
+  where block = read $ c:b:a:[]
+
+sig = "9102llaf"