add files from home for previous chapters and sandboxes

1 files changed, 28 insertions, 0 deletions

diff --git a/sandbox.hs b/sandbox.hs
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+++ b/sandbox.hs
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+import Control.Monad
+import Data.Monoid
+
+dotest x = do
+    if x then return "Test"
+         else return "OK" 
+
+type KnightPos = (Int, Int)
+
+moveKnight :: KnightPos -> [KnightPos]
+moveKnight (c, r) = do
+    (c', r') <- [(c+2,r-1),(c+2,r+1),(c-2,r-1),(c-2,r+1)
+            ,(c+1,r-2),(c+1,r+2),(c-1,r-2),(c-1,r+2)]
+    guard (c' `elem` [1..8] && r' `elem` [1..8])
+    return (c', r')
+
+filterDup :: [KnightPos] -> [KnightPos]
+filterDup [] = []
+filterDup (x:xr) = x:(filterDup $ filter (x/=) xr)
+
+singleStep x = filterDup $ x >>= moveKnight
+
+multiStep :: Int -> [KnightPos] -> [KnightPos]
+multiStep 0 x = x
+multiStep n x = multiStep (n-1) (singleStep x)
+
+applyLog :: (Monoid m) => (a, m) -> (a -> (b, m)) -> (b, m)
+applyLog (x, log) f = let (y, newLog) = f x in (y, log `mappend` newLog)