[clean-list] questions about Clean learning

[Jigang Sun]

Hi,

I have questions about Clean learning. Would anyone help?

On page 95 of Clean textbook, section 4.1.5 Type constructor classes, I do not understand the data structure of "::Tree a = Node a [Tree a]". Would anyone please give an instance of it.

Also, I could not find an explanation for "Just" and "Nothing" in "::MayBe a =Just a| Nothing".

On page 96, section 4.2 Existential types, ::List a = Cons a (List a) | Nil, "Cons" and "Nil" seems to be a keyword, but with no explanations. Can anyone give an example for the structure?

Do anyone know whether there are sample answers to exercises on the Clean Book?

Regards

Jigang