That is using Maybe and is not a null pointer! Just and Nothing are the constructors of Maybe. On Tue, Dec 18, 2018 at 03:43:35PM +0100, Damien Mattei wrote:
thank you Tom, it is the kind of answer that help me i insert this and it is ok now: forM_ bd_rows_WDS $ \(Only x) -> case x of Nothing -> putStrLn ("x =" ++ "NULL") Just x -> putStrLn $ ("x =" ++ Text.unpack x) i had seen a such solution on web but thought the Maybe was the solution, i hoped asked could avoid using sort of Null pointer as mentioned in this article: https://www.lucidchart.com/techblog/2015/08/31/the-worst-mistake-of-computer... if someone else have a simpler solution email me
Le 18/12/2018 13:34, tom.stejskal a écrit :
case x of Nothing -> putStrLn "NULL" Just y -> putStrLn $ Text.unpack y