For anyone reading this, I want to confirm that mightybyte's code would be far more idiomatic. I would never use integer error codes in a Haskell program, but

For anyone reading this, I want to confirm that mightybyte's code would be far more idiomatic. I would never use integer error codes in a Haskell program, but I wanted to make the clear connection to C idioms. Also, using the errors package would be more appropriate than rolling your own function there, but I wanted to emphasize that it was simple, two line function, and not any fancy wizardry that requires caring about category theory. EDIT: rechecking the errors library, the final line would probably be more clear with atNote "Not enough lines" lines 10