[Haskell-beginners] one more step backwards

[Stephen Tetley]

On 31 January 2010 19:53, Felipe Lessa <felipe.lessa at gmail.com> wrote:

> Along these lines we may also change evalStep using the Writer
> monad.

Hi Felipe - nice!

Bill Harrison lists DebugT (equipped with the non-proper morphism
'rollback') as one of the monad transformers in his periodic table of
effects:

http://www.cs.missouri.edu/~harrisonwl/Presentations/UIUCFM05.ppt

I've been curious since first seeing the slides, how an implementation
might efficiently store the state...

Best wishes

Stephen