Add BooleanTrigger

include/dsp/digital.hpp

@@ -8,7 +8,6 @@ namespace rack {
 
 /** Turns HIGH when value reaches 1.f, turns LOW when value reaches 0.f. */
 struct SchmittTrigger {
-	// UNKNOWN is used to represent a stable state when the previous state is not yet set
 	enum State {
 		UNKNOWN,
 		LOW,
@@ -58,6 +57,23 @@ struct SchmittTrigger {
 };
 
 
+struct BooleanTrigger {
+	bool lastState;
+
+	BooleanTrigger() {
+		reset();
+	}
+	void reset() {
+		lastState = true;
+	}
+	bool process(bool state) {
+		bool triggered = (state && !lastState);
+		lastState = state;
+		return triggered;
+	}
+};
+
+
 /** When triggered, holds a high value for a specified time before going low again */
 struct PulseGenerator {
 	float time;