thank you, i understand the difference, but can not see a solution, seems i need main :: IO so keep code in main, which is not really a problem, but i wanted to structure it more... i will keep searching a solution, understanding more haskell Le 10/12/2018 16:06, Francesco Ariis a écrit :
On Mon, Dec 10, 2018 at 03:46:46PM +0100, Damien Mattei wrote:
query returns a list i suppose because i can wirte this in my main code: bd_rows <- query conn qry_head (Only (name::String))
`query` does not return a `[r]`, rather an `IO [r]`. The difference is very important; if you don't get it you will always have troubles with Haskell. This will for sure help you
https://www.seas.upenn.edu/~cis194/fall16/lectures/06-io-and-monads.html _______________________________________________ Beginners mailing list Beginners@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
-- Damien.Mattei@unice.fr, Damien.Mattei@oca.eu, UNS / OCA / CNRS