2016 Update

Task/Temperature-conversion/Haskell/temperature-conversion-1.hs

@@ -0,0 +1,16 @@
+import System.Exit (die)
+import Control.Monad (mapM_)
+
+main = do
+  putStrLn "Please enter temperature in kelvin: "
+  input <- getLine
+  let kelvin = read input
+  if kelvin < 0.0
+      then die "Temp cannot be negative"
+      else mapM_ putStrLn $ convert kelvin
+
+convert :: Double -> [String]
+convert n = zipWith (++) labels nums
+    where labels      = ["kelvin: ", "celcius: ", "farenheit: ", "rankine: "]
+          conversions = [id, subtract 273, subtract 459.67 . (1.8 *), (*1.8)]
+          nums        = (show . ($n)) <$> conversions

Task/Temperature-conversion/Haskell/temperature-conversion-2.hs

@@ -0,0 +1,24 @@
+{-# LANGUAGE LambdaCase #-}
+
+import System.Exit (die)
+import Control.Monad (mapM_)
+import Control.Error.Safe (tryAssert, tryRead)
+import Control.Monad.Trans (liftIO)
+import Control.Monad.Trans.Except
+
+main = putStrLn "Please enter temperature in kelvin: " >>
+       runExceptT getTemp >>=
+       \case Right x  -> mapM_ putStrLn $ convert x
+             Left err -> die err
+
+convert :: Double -> [String]
+convert n = zipWith (++) labels nums
+    where labels      = ["kelvin: ", "celcius: ", "farenheit: ", "rankine: "]
+          conversions = [id, subtract 273, subtract 459.67 . (1.8 *), (1.8 *)]
+          nums        = (show . ($ n)) <$> conversions
+
+getTemp :: ExceptT String IO Double
+getTemp = do
+    t <- liftIO getLine >>= tryRead "Could not read temp"
+    tryAssert "Temp cannot be negative" (t>=0)
+    return t

Task/Temperature-conversion/Haskell/temperature-conversion.hs

@@ -1,18 +0,0 @@
-main = do
-  putStrLn "Please enter temperature in kelvin: "
-  input <- getLine
-  let kelvin = read input :: Double
-  if
-    kelvin < 0.0
-  then
-    putStrLn "error"
-  else
-    let
-      celsius = kelvin - 273.15
-      fahrenheit = kelvin * 1.8 - 459.67
-      rankine = kelvin * 1.8
-    in do
-      putStrLn ("kelvin: " ++ show kelvin)
-      putStrLn ("celsius: " ++ show celsius)
-      putStrLn ("fahrenheit: " ++ show fahrenheit)
-      putStrLn ("rankine: " ++ show rankine)