[Haskell-beginners] (SPAM 3)Re: (SPAM 3)Re: monad and variable result

[Damien Mattei]

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
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-- 
Damien.Mattei at unice.fr, Damien.Mattei at oca.eu, UNS / OCA / CNRS