[Haskell-cafe] Field updates in a state monad

10 Jan 2008

      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?

Michael

[Haskell-cafe] Field updates in a state monad

Michael Roth