-type bucket() ::
          #{index := bucket_index(),
            lower := float(),
            upper := float() | infinity,
            count := pos_integer()}.

A single non-empty bucket of a DDSketch.

count values were inserted into the bucket, and all of them fall within (lower, upper], with the exception of the zero bucket, for which both lower and upper are 0.0.

Note that the bounds are the ones the bucket is defined by, not the ones of the values actually inserted: for the smallest bucket of a saturated ddskerl_bound sketch, which collapses buckets on demand, lower is only a lower estimate.

-type bucket_index() :: integer() | zero | underflow | overflow.

Index identifying a bucket within a DDSketch.

A regular bucket is identified by an integer I and covers the values in the interval (gamma^(I-1), gamma^I]. Values that cannot be indexed that way are accumulated in the following special buckets:

• zero, for values of exactly zero, as log(0) is undefined;
• underflow, for values too small for the smallest allocated bucket;
• overflow, for values too large for the largest allocated bucket.

Which of the special buckets a given implementation uses depends on whether its buckets are preallocated, see bucket/0.

-type ddsketch() ::
          ddskerl_std:ddsketch() |
          ddskerl_bound:ddsketch() |
          ddskerl_ets:ddsketch() |
          ddskerl_counters:ddsketch().

DDSketch instance.

-type opts() :: #{atom() => dynamic()}.

Options for the DDSketch.