Hi! I have made this function to generate a random graph for Data.Graph.Inductive library: generateGraph :: Int -> IO (Gr String Double) generateGraph graphSize = do when (graphSize < 1) $ throwIO $ AssertionFailed $ "Graph size out of bounds " ++ show graphSize let ns = map (\n -> (n, show n)) [1..graphSize] es <- fmap concat $ forM [1..graphSize] $ \node -> do nedges <- randomRIO (0, graphSize) others <- fmap (filter (node /=) . nub) $ forM [1..nedges] $ \_ -> randomRIO (1, graphSize) gen <- getStdGen let weights = randomRs (1, 10) gen return $ zip3 (repeat node) others weights return $ mkGraph ns es But I noticed that graph has sometimes same weights on different edges. This is very unlikely to happen so probably I have some error using random generators. Could somebody tell me where? Mitar