That helps IMMENSELY!

I shall see if there is errata on the book's web presence. 

Thanks,

Trent.

On Wed, Aug 15, 2018 at 10:22 AM Francesco Ariis <fa-ml@ariis.it> wrote:
Hello Trent,

On Wed, Aug 15, 2018 at 10:08:29AM -0700, trent shipley wrote:
> Also, at this point I am having trouble reading these function declarations.
>
> all :: (a -> Bool) -> [Bool] -> Bool
> all b ls = and (map b ls)

There must be a typo in the text. The correct signature is

    all :: (a -> Bool) -> [a] -> Bool

Which is logical:
    - we take a list of `a`s (`[a]`)
    - we pass them through a function `a -> Bool`,
      obtaining `[Bool]`
    - we check if the resulting list is all comprised of `True`s.

Does that help?
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