A bounded heap of values of type 'a.

create n is a heap that holds at most n elements.

An element in a heap.

The index of an entry.

ptr e is the index of e.

• raises Invalid_arg

  if e has already been freed.

alloc t a ~extra_data adds the value a to t and returns a pointer to that value, or raises Invalid_argument if no extra space can be created for t, or t has already been released.

• parameter extra_data

  Prevent this from being GC'd until free is called.

free t p returns the element referenced by p and removes it from the heap. Has undefined behaviour if p has already been freed.

in_use t is the number of entries currently allocated.

release t marks t as unusable. Future operations on it will fail. t must be idle.

is_released t is true once release has succeeded.