On Jan 30, 2008 12:44 AM, Adam Smyczek <adam.smyczek@gmail.com> wrote:

Hi,

My application has to manage a data set. I assume the state monad is
designed for this.
The state changes in functions that:
a. perform IO actions and
b. return execution status and execution trace (right now I'm using
WriteT for this).

Is the best solution:
1. to build a monad stack (for example State -> Writer -> IO) or
2. to use IORef for the data set or
3. something else?

Are monad stacks with 3 and more monads common?
How could an example implementation look like?

Hi Adam,

Indeed, this is quite common.  You may be interested in reading

  http://cale.yi.org/index.php/How_To_Use_Monad_Transformers

Good luck!
-Brent