2011/9/6 Poprádi Árpád <popradi_ar...@freemail.hu>: > i have a record with a lot of items used in a state monad. > > data BigData = BigData { > data1 :: X > , data2 :: X > -- and so on > } > > updateData1 :: X -> MonadicEnv() > updateData1 d = do; env <- get; put env {data1 = d} > > updateData2 :: X -> MonadicEnv() > updateData2 d = do; env <- get; put env {data2 = d} > > But it's ugly. Always the same, only the record selector has another > name. > Is it possible to generalize it?
You can use the fclabels package [1] for this. It makes record labels first class, and also provides functions to update parts of a record in the state monad [2]. You would be able to write something like: updateData1 = puts data1 d It has a function for modifcation as well, which is even uglier with regular record syntax. Erik [1] http://hackage.haskell.org/package/fclabels [2] http://hackage.haskell.org/packages/archive/fclabels/1.0.4/doc/html/Data-Label-PureM.html#v:puts _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe