[exercise] 5.8

Author: Dev-XYS

chapter05-List-comprehensions/8.hs

@@ -0,0 +1,5 @@
+find :: Eq a => a -> [(a, b)] -> [b]
+find k t = [v | (k', v) <- t, k == k']
+
+positions :: Eq a => a -> [a] -> [Int]
+positions x xs = find x [(x, i) | (x, i) <- zip xs [0..]]