1 files changed, 104 insertions, 0 deletions
diff --git a/sem7/pp/lec6.hs b/sem7/pp/lec6.hs
new file mode 100644
index 0000000..4598d7a
--- /dev/null
+++ b/sem7/pp/lec6.hs
@@ -0,0 +1,104 @@
+import Data.Maybe
+
+-- Probably not the fastest way
+ones :: Integral a => [a]
+ones = 1 : ones
+
+allnums :: Integral a => [a]
+allnums = 0 : zipWith (+) allnums ones
+
+threes :: Integral a => [a]
+threes = filter ((==0) . flip rem 3) allnums 
+
+data Doll = Shell Doll | Infant
+
+size' :: Doll -> Int
+size' Infant = 1
+size' (Shell d) = 1 + size' d
+
+yeahVeryCool = size' . Shell . Shell . Shell $ Infant
+
+data BExp = BTrue | BFalse | Or BExp BExp | And BExp BExp | Not BExp
+
+yoyo = Not (Or (And BTrue BFalse) BTrue)
+
+eval' :: BExp -> Bool
+eval' BTrue = True
+eval' BFalse = False
+eval' (Not e) = not . eval' $ e
+eval' (And a b) = eval' a && eval' b
+eval' (Or a b) = eval' a || eval' b
+
+
+perfectSq = flip take [x * x | x <- [0..]]
+-- Alternative
+perfectSq' n = [x * x | x <- [0..n]]
+
+isprime :: Integral a => a -> Bool
+isprime x = not . any ((==0) . rem x) $ [2..(x-1)]
+isprime' x = null [x | n <- [2..(x-1)], rem x n == 0]
+
+data Nat = Zero | Suc Nat
+
+nat2int :: Nat -> Int
+nat2int Zero = 0
+nat2int (Suc n) = 1 + nat2int n
+
+int2nat :: Int -> Nat
+int2nat 0 = Zero
+int2nat x | x > 0 = Suc . int2nat $ (x-1)
+          | otherwise = Zero
+
+fibs :: [Int]
+fibs = 1 : 1 : fibsfunc 1 1
+  -- from lastlast and last (sorry)
+  where fibsfunc ll l = e : fibsfunc l e
+          where e = l + ll
+
+
+fib :: Int -> [Int]
+fib = flip take fibs
+
+data Tree a = Leaf a | Node (Tree a) (Tree a)
+
+mzipThing :: (a -> b -> Maybe c) -> Maybe a -> Maybe b -> Maybe c
+mzipThing _ Nothing _ = Nothing
+mzipThing _ _ Nothing = Nothing
+mzipThing func (Just a) (Just b) = func a b
+
+nodeCompare :: Int -> Int -> Maybe Int
+nodeCompare a b | a == b = Just (a+1)
+          | otherwise = Nothing
+
+balancedWithLen :: Tree a -> Maybe Int
+balancedWithLen (Leaf _) = Just 0
+balancedWithLen (Node a b) = mzipThing nodeCompare (balancedWithLen a) (balancedWithLen b)
+
+balanced :: Tree a -> Bool
+balanced = isJust . balancedWithLen
+ 
+notCoolTree = Node (Node (Leaf 1) (Node (Leaf 1) (Leaf 1))) (Leaf 1)
+coolTree = Node (Leaf 1) (Leaf 1)
+
+
+any' :: (a -> Bool) -> [a] -> Bool
+any' _ [] = False
+any' func (x:xs) = func x || any' func xs
+
+anyWithFold :: (a -> Bool) -> [a] -> Bool
+anyWithFold func = foldl (\x y -> x || func y) False
+
+filterWithFold :: (a -> Bool) -> [a] -> [a]
+filterWithFold func = foldr (\new pre -> if func new
+                                            then new:pre
+                                            else pre
+                            ) []
+
+
+-- Problems part of larger thing
+data LTreeMid = LLeaf Char | LNode LTreeMid LTreeMid
+data LTree = LTree LTreeMid Float
+
+treemerge :: LTree -> LTree -> LTree
+treemerge (LTree ta la) (LTree tb lb) = LTree (LNode ta tb) (la + lb)
+