`val make : 'a -> 'a t`

`make x`

creates an infinite array, where every slot contains `x`

. *

`val get : 'a t -> int -> 'a`

`get a i`

returns the element contained at offset `i`

in the array `a`

. Slots are numbered 0 and up. *

`val set : 'a t -> int -> 'a -> unit`

`set a i x`

sets the element contained at offset `i`

in the array `a`

to `x`

. Slots are numbered 0 and up. *

`val extent : 'a t -> int`

`extent a`

is the length of an initial segment of the array `a`

that is sufficiently large to contain all `set`

operations ever performed. In other words, all elements beyond that segment have the default value.

`val domain : 'a t -> 'a array`

`domain a`

is a fresh copy of an initial segment of the array `a`

whose length is `extent a`

.