Re: [Haskell-cafe] Accumulator value for "and" and "or"

PR Stanley:

or = foldl (||) False and = foldl (&&) True [...] Other than the practical convenience is there a reason for having the empty list in and and or equating to True and False?

It might help to think of "and" as a kind of product, and "or" as a kind of sum, and note that: sum [] = 0 product [] = 1 If it seems odd that the product of an empty list should be 1, then consider why x^0 = 1 for any x /= 0, and so on.