doc-src/TutorialI/ToyList2/ToyList1

adapted deriv;

theory ToyList = PreList:;

datatype 'a list = Nil                          ("[]")
                 | Cons 'a "'a list"            (infixr "#" 65);

consts app :: "'a list => 'a list => 'a list"   (infixr "@" 65)
       rev :: "'a list => 'a list";

primrec
"[] @ ys       = ys"
"(x # xs) @ ys = x # (xs @ ys)";

primrec
"rev []        = []"
"rev (x # xs)  = (rev xs) @ (x # [])";