list comprehension practice

comprehensions.hs

@@ -0,0 +1,23 @@
+-- LIST COMPREHENSION EXCERCISES
+
+--repl n e = take n (cycle [e])
+repl n e = [e | x <- [1..n]]
+
+allStrings _ 0 = []
+allStrings letters n = [[l] | l <- letters] ++ [l : built | l <- letters, built <- allStrings letters (n-1)]
+
+palindromes strings = [x ++ y | x <- strings, y <- strings, (x ++ y) == reverse (x ++ y)]
+
+factors n = [x | x <- [2..n-1], n `mod` x == 0]
+
+pythagoreanTriads n = let numbersToN = [1..n]
+                    in [[a, b, c] | a <- numbersToN, b <- numbersToN, c <- numbersToN, a^2 + b^2 == c^2]
+
+type Coin = Int
+coins :: [Coin]
+--coins = reverse (sort [1,2,5,10,20,50,100])
+coins = [100,50,20,10,5,2,1]
+
+change 0 = []
+change n = let largestCoin = head [coin | coin <- coins, coin <= n]
+            in largestCoin : change (n-largestCoin)