An example of use is in our race brakes. Because we only want the brake bias to be tuneable with the full race brake setup, but the user can add only front or rear race brakes if they want, we used in the rear brake part: {"brakeTorque":"$=$brakebias == nil and $brakestrength*1000 or $brakestrength*4000*(1-$brakebias)"} This way, if the front race brakes (which initialize the $brakebias variable) are not present, it doesn't try and fail to do the math with that variable. Using these logic operators mean you could make basically any parameter of jbeam dependent on some conditions (within the variable system) rather than just a regular math operations.
