Re: [Haskell-cafe] Field updates in a state monad

On Thu, 10 Jan 2008, Michael Roth wrote:

Hello list,

still playing with monads and states, I have the following question:

Given:

import Control.Monad.State.Lazy

data MyData = MyData { content :: String }

foobar :: State MyData String foobar = do gets content

Ok, that looks nice and tidy. But:

foobar2 :: State MyData () foobar2 = do modify $ \x -> x { content = "hello haskell"}

...looks not so nice.

Exists there a way to write this cleaner without writing countless "set_xyz" helper functions?

http://www.haskell.org/haskellwiki/Record_access