mrloop | An event loop for C | Reactive Programming library

The first version recurses forever because the mrLoop a (b+1) action is outside the if/else expression.

In other words, it either does nothing or prints a*b, and then it unconditionally recurses into mrLoop a (b+1). It'll keep recursing forever.

In the latter example, recursion stops when the pattern-matched function hits the base case where b is 10.

Your friend probably means that this isn't the Haskell way because the Haskell way is to separate pure functions from impure actions.

Try if you can write the recursive 'loop' as a pure function (i.e. without IO). What would it return? How could you then use that return value to print a series of results?