Hi everyone, I have just started learning Haskell, it is a very interesting language. As a first project, I am building a brainfuck interpreter, but have hit a stumbling block: IO. My program source is located at http://hpaste.org/11219 My program handles the state of a brainfuck program by passing State(lists of ints) objects around. When I added my getIn fuction, however, it needed to return an IO State object. This broke the run function, as it returned a State. No problem, I thought, and changed run to return IO State. This broke my exec function, which calls run on each element in a list. As exec passes on the state returned by the run function to itself, it needs to take an IO State. This causes problems in the loop function, which calls exec on a subprogram. Because exec now takes IO State, loop also needs to. However, loop is called by run, so now run needs to take IO State. Now, all functions called by run need to take IO State. All this creates a whole load of functions with IO, even though it should not be necessary. What I would like to know, is how I can avoid this, possibly by modifying exec to just take a State. Whew! What a long-winded explanation! Any ideas? --Jamie P.S. Please ignore my long-winded list iteration functions -- I'm working on a cleaner version.