reservoir sampling
type 'a t
a random sample of 'a values
val create : ?random_state:Core.Std.Random.State.t -> int -> 'a t
create ~random_state desired_sample_size creates an empty sample of 'a values. The sample will grow no larger than desired_sample_size when presented with more values by calling add.
val desired_sample_size : 'a t -> int
the desired sample size
val maybe_add : 'a t -> 'a -> unit
maybe_add t x will randomly either add x to t or ignore it. If adding x would grow the sample larger than desired_sample_size t, some previously selected value will be discarded.
val to_list : 'a t -> 'a list
the current selection from values previously seen by t. Of all previously seen values, each subset of size desired_sample_size t is equally likely to have been selected.
val select : ?random_state:Core.Std.Random.State.t ->
next:(unit -> 'a option) -> int -> 'a list
randomly select a subset of size sample_size from a stream of unknown length. Each possible subset is chosen with equal probability.