lab08: init

lab08/benderPerhaps.hs

@@ -0,0 +1,34 @@
+import Data.Map (Map)
+import qualified Data.Map as Map
+
+-- In this code, we model bender moving around, but
+-- if he finds beer, he will stop responding to commands.
+type Pos = (Integer, Integer)
+
+x -: f = f x
+
+start = (0,0)
+
+badPos = Map.empty
+  -: Map.insert (0,2) True
+  -: Map.insert (-1,3) True
+  -: Map.insert (-3,-8) True
+
+
+moveTo :: Pos -> Maybe Pos
+moveTo p =
+  if Map.member p badPos
+    then Nothing
+    else Just p
+
+up (x, y)    = moveTo (x, y+1)
+down (x, y)  = moveTo (x, y-1)
+left (x, y)  = moveTo (x-1, y)
+right (x, y) = moveTo (x+1, y)
+
+-- Our directions now result in Maybe Pos values, so we can't chain them with "-:" anymore.
+test1 = return start >>= up >>= right
+test2 = return start >>= up >>= left >>= left >>= right >>= down
+test3 = return start >>= left >>= left >>= up >>= up >>= right >>= up >>= right >>= right >>= down
+
+