But instead of using IO, I wanted to make my own pure monad that gets evaluated with interact, and does the same.
However, I get the following output:
Enter your name:
Welcome ......
So the Welcome is printed too soon.
This is obvious since my monad is lazy, so I tried to put a seq at some strategic places to get the same behavior as IO. But I completely failed doing so, either the program doesn't print anything and asks input first, or it still prints too much output.
Of course I could just use ST, State, transformers, etc, but this is purely an exercise I'm doing.
So, I could re-read all papers and look in detail at all the code, but maybe someone could help me out where to put the seq or what to do :-)
Oh btw, the usage of DList here might not be needed; intuitively it felt like the correct thing to do, but when it comes to Haskell, my intuition is usually wrong ;-)
Thanks a lot,
Peter Verswyvelen