I was developing a web site using haskell programs as cgi's, and I found a strange behavior that I would like to know whether it is normal. I have reduced the "problem" to the next program: fEntrada = "fich.txt" fSalida = "fich.txt" creaFich :: IO() creaFich = writeFile fEntrada "me molo" main :: IO () main = do x <- readFile fEntrada -- print x -- In the second try, uncomment this line writeFile fSalida "" writeFile fSalida x Running the next commands (suposing that $ is the prompt of a linux shell and main> is the prompt of hugs) main> creaFich main> main $ cat fich.txt will give us different results if we comment or uncomment the second line of the main body, although the meaning of the program is the same. I understand that this is caused by the lazyness, that doesn't evaluate the expression "x <- readFile fEntrada" until it's necessary, but.. is it normal that we have to think about this "problem" when programming? In my case, this behavior caused my program to fail (and it was really complicated to find why) and the only solution I found was indeed printing to a scratch file the string I was reading inmediatly after reading it (really, after telling hugs to read it). I find this a great disadvantage as oppose of the imperative paradigm, overall because is like having to control something (near to concurrence if you ask me) that has not been asked for! I 'll be thankful of any comments or replies you send to me. Greetings, Diego y tal <deigote@gmail.com>