Hi Tomek!
In a CGI application I was gathering SQL statements I wanted to run in the final transaction. Because I use haskelldb, it was most convenient to use (Database -> IO ()) as the type of the statement or a group of statements. In this representation concatenating two statement groups so they are executed in sequence can be done with:
concatStmts s1 s2 = \db -> s1 db >> s2 db
My mistake was that I forgot about db and wrote:
concatStmts s1 s2 = s1 >> s2
And it was accepted because I had the Monad instance for ((->) r) in scope (from Control.Monad.Trans I guess)!
Have you considered changing the statements to have type 'ReaderT Database IO ()'? Then (>>) actually does what you want. Pozdrawiam, Arie -- Always go along with the group, or someone may drop a sixteen-ton safe on you. - The Buddy Bears