lab04: impl

lab04/mapFilter.hs

@@ -1,17 +1,23 @@
 -- USING MAP, convert a list of Strings to a list of Integers.
 stringsToNums :: [String] -> [Integer]
+stringsToNums l = map read l
 
 
 -- USING MAP, take a list of integers and return a list with
 -- the equivalent absolute values.
+mapAbsVal :: [Integer] -> [Integer]
+mapAbsVal l = map abs l
 
 
 -- USING ZIPWITH, concatenate a list of first names with
 -- a list of last names to produce a list of full names.
-
+fullNames :: [String] -> [String] -> [String]
+fullNames l = zipWith (\first last -> first ++ " " ++ last) l
 
 -- USING MAP AND FILTER, square all positive numbers in a list;
 -- strip out 0 and negative numbers.
+squarePositives :: [Integer] -> [Integer]
+squarePositives l = map (\x -> x * x) $ filter (\x -> x > 0) l
 
 
 main :: IO ()
@@ -21,5 +27,4 @@ main = do
   print $ mapAbsVal [-4, 3, 2, -99, 54]
   print $ mapAbsVal $ stringsToNums ["-4", "7", "-22"]
   print $ fullNames ["John", "Wes Happen", "Holly"] ["Smith", "Ng", "Wood"]
-  print $ squarePostives [2, -3, 45, 5, 0, 7, -6]
-  
+  print $ squarePositives [2, -3, 45, 5, 0, 7, -6]