Janis Voigtländer writes:
One answer I could give is: That depends on the definition of the Traversable instance for the (Bool -> a) type constructor.
Another answer I could give is: Ask the authors of the Traversable documentation. [..]
Since Charles had not mentioned Traversable in his messages, I still find the original question 2 to be ambiguous. If one has a Traversable instance, then he can say what being left fold-like means for a function. As far as I understand, however, this should be equivalent to the property of being extensionally equal to the foldl1 of the Foldable superclass, provided instances follow the laws. Please, again, correct me if I am wrong. I want to remark that mine is not criticism towards Charles's message: on the contrary, I think that starting a discussion on not completely specified ideas can be very beneficial for everyone, as several people at once will make some effort to get a clearer understanding, sharing their points of view. Thanks for taking the time to explain your interpretation. Best, Matteo