I have tried using this with a few different boards and get different messsages, here is the one when using Arduino Uno:
Build options changed, rebuilding all
Smoothed:18:1: error: 'Smoothed' is not a template
Smoothed mySensor;
^
Smoothed:19:1: error: 'Smoothed' is not a template
Smoothed mySensor2;
^
C:\Users\patri\Documents\Arduino\libraries\Smoothed\examples\Smoothed\Smoothed.ino: In function 'void loop()':
Smoothed:14:20: error: expected primary-expression before '=' token
#define SENSOR_PIN = A0; // The input pin for the sensor. In this example we are reading from an Arduino analogue pin.
C:\Users\patri\Documents\Arduino\libraries\Smoothed\examples\Smoothed\Smoothed.ino:55:41: note: in expansion of macro 'SENSOR_PIN'
float currentSensorValue = analogRead(SENSOR_PIN);
Smoothed:55:51: error: expected primary-expression before ')' token
float currentSensorValue = analogRead(SENSOR_PIN);
exit status 1
'Smoothed' is not a template