Module Lazy: deferred computations.
type 'a status =
| Delayed of (unit -> 'a)
| Value of 'a
| Exception of exn
type 'a t = 'a status ref;;
A value of type 'a Lazy.t is a deferred computation (called a
suspension) that computes a result of type 'a. The expression
lazy (expr) returns a suspension that computes expr.
val force: 'a t -> 'a;;
Lazy.force x computes the suspension x and returns its result.
If the suspension was already computed, Lazy.force x returns the
same value again. If it raised an exception, the same exception is