Edge Primitives

Edge primitives detect transitions in trigger / control signals and accumulate counts. All four variants share one backing opcode (EDGE_OP) for cache locality and consistent state semantics.

sah

Sample and hold. Latches the current value of in whenever trig crosses zero from below. The held value is broadcast to every sample of the output until the next rising edge.

Param	Type	Default	Description
in	signal	-	Signal to sample
trig	signal	-	Trigger signal (rising edge captures)

// Sample noise once per beat
noise() |> sah(%, trigger(1)) |> out(%, %)

gateup

Rising-edge detector. Outputs 1.0 on the single sample where sig transitions from <= 0 to > 0, otherwise 0.0.

Param	Type	Default	Description
sig	signal	-	Signal to monitor

// Trigger an envelope on every rising edge of an LFO
gate = gateup(lfo(2))
ar(gate, 0.01, 0.3) * osc("sin", 880) |> out(%, %)

gatedown

Falling-edge detector. Outputs 1.0 on the single sample where sig transitions from > 0 to <= 0, otherwise 0.0. Useful for note-off events.

Param	Type	Default	Description
sig	signal	-	Signal to monitor

// Fire a percussive blip on note-off
release = gatedown(gate_signal)
ar(release, 0.001, 0.05) * noise() |> out(%, %)

counter

Accumulator. Increments by 1.0 on every rising edge of trig. Optionally resets to start (default 0) on every rising edge of reset. If trig and reset fire on the same sample, reset wins (the increment is skipped that sample).

Param	Type	Default	Description
trig	signal	-	Increment trigger (rising edge)
reset	signal	(none)	Optional reset trigger (rising edge)
start	signal	0	Optional reset target value

// Bare counter, never resets
n = counter(trigger(1))

// Reset every 4 beats
n = counter(trigger(4), beat(4))

// Reset to 7 instead of 0
n = counter(trigger(4), beat(4), 7)

// Index into an array of MIDI notes
notes = [60, 64, 67, 72]
notes[counter(trigger(4))] |> mtof(%) |> sine(%) |> out(%, %)

counter is the natural pair with array indexing, since ARRAY_INDEX wraps by default: an unbounded counter index always produces an in-range lookup.

Related: state, Method calls