CODEWITHSUNDEEP
recursiontypesocaml
David 天宇 Wong
David 天宇 Wong

Reputation: 4177

infinitely recursive type in OCaml

I'm reading this OCaml file and it contains the following:

type z = Z of z

This looks like z is infinitely recursive. How is it useful and how can I even construct such a type?

Upvotes: 2

Views: 162

Answers (1)

Jeffrey Scofield
Jeffrey Scofield

Reputation: 66818

I don't think this type is particularly useful, except possibly as a test case in type theory.

You can construct values of the type like this:

# let rec x = Z x;;
val x : z = Z <cycle>
# let rec q = Z (Z q);;
val q : z = Z (Z <cycle>)

Once you have a value of the type you can readily construct other values of course:

# let y = Z (Z x);;
val y : z = Z (Z (Z <cycle>))

Upvotes: 6

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