2016 Update

Task/Parsing-RPN-calculator-algorithm/Haskell/parsing-rpn-calculator-algorithm-1.hs

@@ -0,0 +1,13 @@
+calcRPN :: String -> [Double]
+calcRPN = foldl interprete [] . words
+
+interprete s x
+  | x `elem` ["+","-","*","/","^"] = operate x s
+  | otherwise = read x:s
+  where
+    operate op (x:y:s) = case op of
+      "+" -> x + y:s
+      "-" -> y - x:s
+      "*" -> x * y:s
+      "/" -> y / x:s
+      "^" -> y ** x:s

Task/Parsing-RPN-calculator-algorithm/Haskell/parsing-rpn-calculator-algorithm-2.hs

@@ -0,0 +1,6 @@
+calcRPNLog :: String -> ([Double],[(String, [Double])])
+calcRPNLog input = mkLog $ zip commands $ tail result
+  where result = scanl interprete [] commands
+        commands = words input
+        mkLog [] = ([], [])
+        mkLog res = (snd $ last res, res)

Task/Parsing-RPN-calculator-algorithm/Haskell/parsing-rpn-calculator-algorithm-3.hs

@@ -0,0 +1,7 @@
+import Control.Monad (foldM)
+
+calcRPNIO :: String -> IO [Double]
+calcRPNIO = foldM (verbose interprete) [] . words
+
+verbose f s x = write (x ++ "\t" ++ show res ++ "\n") >> return res
+  where res = f s x

Task/Parsing-RPN-calculator-algorithm/Haskell/parsing-rpn-calculator-algorithm-4.hs

@@ -0,0 +1,10 @@
+class Monad m => Logger m where
+  write :: String -> m ()
+
+instance Logger IO where write = putStr
+instance a ~ String => Logger (Writer a) where write = tell
+
+verbose2 f x y = write (show x ++ " " ++
+                        show y ++ " ==> " ++
+                        show res ++ "\n") >> return res
+  where res = f x y

Task/Parsing-RPN-calculator-algorithm/Haskell/parsing-rpn-calculator-algorithm-5.hs

@@ -0,0 +1,2 @@
+calcRPNM :: Logger m => String -> m [Double]
+calcRPNM = foldM (verbose interprete) [] . words

Task/Parsing-RPN-calculator-algorithm/Haskell/parsing-rpn-calculator-algorithm.hs

@@ -1,15 +0,0 @@
-import Data.List (elemIndex)
-
--- Show results
-main = mapM_ (\(x, y) -> putStrLn $ x ++ " ==> " ++ show y) $ reverse $ zip b (a:c)
-        where (a, b, c) = solve "3 4 2 * 1 5 - 2 3 ^ ^ / +"
-
--- Solve and report RPN
-solve = foldl reduce ([], [], []) . words
-reduce (xs, ps, st) w =
-    if i == Nothing
-        then (read w:xs, ("Pushing " ++ w):ps, xs:st)
-        else (([(*),(+),(-),(/),(**)]!!o) a b:zs, ("Performing " ++ w):ps, xs:st)
-    where   i = elemIndex (head w) "*+-/^"
-            Just o = i
-            (b:a:zs) = xs