+import "Prelude"\r
+\r
+a :: [Either Integer Integer]\r
+a = [Left 1, Right 2, Left 3, Right 4]\r
+\r
+lefts :: [Either a b] -> [a]\r
+lefts l = [x | Left x <- l] \r
+\r
+main :: [Integer]\r
+main = lefts a\r
+--\r
+[1, 3]
\ No newline at end of file