Function evaluate

docs/app/js/sanddance-app.js:107629–107637

* Delegate method to perform operator processing. * Subclasses can override this method to perform custom processing. * By default, it marshalls parameters and calls the update function * if that function is defined. If the update function does not * change the operator value then StopPr

(pulse2)

   * @return The output pulse or StopPropagation. A falsy return value
   *   (including undefined) will let the input pulse pass through.
   */ evaluate (pulse2) {
        const update2 = this._update;
        if (update2) {
            const params = this.marshall(pulse2.stamp), v = update2.call(this, params, pulse2);
            params.clear();
            if (v !== this.value) this.value = v;
            else if (!this.modified()) return pulse2.StopPropagation;
        }
    },
    /**
   * Run this operator for the current pulse. If this operator has already
   * been run at (or after) the pulse timestamp, returns StopPropagation.