I went to check why the hell this happened. It looks like the pair (“(,)”) is defined as an instance of Foldable, for some reason, which is the class used by functions like foldl() and foldr(). Meanwhile, triples and other tuples of higher order (such as triples, quadruples, …) are not instances of Foldable.
The weirdest part is that, if you try to use a pair as a Foldable, you only get the second value, for some reason… Here is an example.
Oddly enough, in Haskell (as defined by the report), length is monomorphic, so it just doesn’t work on tuples (type error).
Due to the way kinds (types of types) work in Haskell, Foldable instances can only operate over (i.e. length only counts) elements of the last/final type argument. So, for (,) it only counts the second part, which is always there exactly once. If you provided a Foldable for (,) it would also have length of 1.
This is my favorite language: GHC Haskell
GHC Haskell:
GHCi> length (2, "foo") 1Wait, now I need to know why.
* some time later *
I went to check why the hell this happened. It looks like the pair (“
(,)”) is defined as an instance ofFoldable, for some reason, which is the class used by functions likefoldl()andfoldr(). Meanwhile, triples and other tuples of higher order (such as triples, quadruples, …) are not instances ofFoldable.The weirdest part is that, if you try to use a pair as a
Foldable, you only get the second value, for some reason… Here is an example.ghci> foldl (\acc x -> x:acc) [] (1,2) [2]This makes it so that the returned length is 1.
Oddly enough, in Haskell (as defined by the report), length is monomorphic, so it just doesn’t work on tuples (type error).
Due to the way kinds (types of types) work in Haskell, Foldable instances can only operate over (i.e. length only counts) elements of the last/final type argument. So, for (,) it only counts the second part, which is always there exactly once. If you provided a Foldable for (,) it would also have length of 1.
I don’t even know Haskell but it seems like (" ( , ) ") would be an instance of boob.
It looks like two worms split running from another tinier worm. Makes you wonder what it has done to be so feared