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module Random_selection

: sig

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

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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.

end