Counter / Average / MovingAverage

Counter

Counter is a lighter-weight, non-threadsafe alternative to AtomicInt. It contains an Int value, with convenience methods such as inc dec etc. that do not return the new value. It is simpler to use than trying to juggle a value on a stack, fetch/increment/put back. It works especially well in a a local variable, eg

: countme
  Counter.new^ l.cnt!
  0 9 range
  foreach
    l.cnt.inc^
  /foreach
  "Count: " $ [email protected] $ nl
;

Average

Average maintains a running average, variance, and N to-date without needing to retain the samples. It is mathematically correct, in the sense that the result is the same as accumulating the samples in a list then iterating an average/variance. Use reset to clear.

Average is threadsafe, and has getMeanAndN and getMeanStdDevAndN methods for getting the values atomically.

MovingAverage

MovingAverage is an exponential moving average (EMA) for signals that drift — live costs, rates, telemetry. Create a default with a roughly 20 item span with MovingAverage.new^. To create with a longer or shorter span, use MovingAverage.newWithSpan^; .span is fixed afterward (effective window in samples). Internally α = 2/(span+1). Same .mean / .n / add / reset / getMeanAndN API as Average, but no variance.

Prefer Average when you need an exact cumulative mean and variance; prefer MovingAverage when recent samples should outweigh old ones (e.g. SimClock update/render costs).