Vietnamese dictionaries for mobile phones

A data type which contains itself. The commonest example is

the list type, in Haskell:

data List a = Nil | Cons a (List a)

which says a list of a's is either an empty list or a conscell containing an 'a' (the "head" of the list) and another

list (the "tail").

Recursion is not allowed in Miranda or Haskell synonymtypes, so the following Haskell types are illegal:

type Bad = (Int, Bad)

type Evil = Bool -@# Evil

whereas the seeminly equivalent algebraic data types are

acceptable:

data Good = Pair Int Good

data Fine = Fun (Bool-@#Fine)