What does the Haskell function forall do and where is it defined?
haskell
Solution
Haha, embarrassed author here.
I invented `forall` to mime `quickCheck` and make intuitive sense, but not to be executable. In my defense, I took inspiration from the Little Schemer which happily introduces syntax and semantics far before they're executable in order to build intuition by practice.
Except, of course, my `forall` is not actually executable at all and it has lead to a lot of confusion.
So, my suggestion to anyone curious is to investigate `quickcheck` as a stand-in for `forall`. My suggestion to myself, now carried out, is to edit the tutorial to note my artistic license there.
Sorry about any trouble.
Problem
I'm reading A Little Lens Starter Tutorial and they use a seemingly magical function `forall` like this: ``` >>> forall $ \tuple -> view _1 tuple == fst tuple True ``` What exactly does this function do and more importantly what package is it from. I can't find it using Hoogle, etc.