tasks a-s

Task/Pascals-triangle/Haskell/pascals-triangle-1.hs

@@ -0,0 +1,4 @@
+zapWith :: (a -> a -> a) -> [a] -> [a] -> [a]
+zapWith f xs [] = xs
+zapWith f [] ys = ys
+zapWith f (x:xs) (y:ys) = f x y : zapWith f xs ys

Task/Pascals-triangle/Haskell/pascals-triangle-2.hs

@@ -0,0 +1,2 @@
+extendWith f [] = []
+extendWith f xs@(x:ys) = x : zapWith f xs ys

Task/Pascals-triangle/Haskell/pascals-triangle-3.hs

@@ -0,0 +1 @@
+pascal = iterate (extendWith (+)) [1]

Task/Pascals-triangle/Haskell/pascals-triangle-4.hs

@@ -0,0 +1,2 @@
+*Main> take 6 pascal
+[[1],[1,1],[1,2,1],[1,3,3,1],[1,4,6,4,1],[1,5,10,10,5,1]]

Task/Pascals-triangle/Haskell/pascals-triangle-5.hs

@@ -0,0 +1,5 @@
+-- generate next row from current row
+nextRow row = zipWith (+) ([0] ++ row) (row ++ [0])
+
+-- returns the first n rows
+pascal = iterate nextRow [1]

Task/Pascals-triangle/Haskell/pascals-triangle-6.hs

@@ -0,0 +1,5 @@
+fac = product . enumFromTo 1
+
+binCoef n k = (fac n) `div` ((fac k) * (fac $ n - k))
+
+pascal n = map (binCoef $ n - 1) [0..n-1]

Task/Pascals-triangle/Haskell/pascals-triangle-7.hs

@@ -0,0 +1,11 @@
+*Main> putStr $ unlines $ map unwords $ map (map show) $ pascal 10
+1
+1 1
+1 2 1
+1 3 3 1
+1 4 6 4 1
+1 5 10 10 5 1
+1 6 15 20 15 6 1
+1 7 21 35 35 21 7 1
+1 8 28 56 70 56 28 8 1
+1 9 36 84 126 126 84 36 9 1