[immortality]

Hi
in Swak postProcessing function below:

totalPressure_left
       {
        type swakExpression;
        valueType patch;
        patchName left;
        accumulations (
            average
        );
        variables (
            "gamma=1.4;"
            "R=287.14;"
        );
        expression "sum(p*(pow(1+(gamma-1)/2*magSqr(U)/(gamma*R*T),(gamma/(gamma-1))))*rho*area())/sum(rho*area())";
        verbose true;
        outputControlMode outputTime;
        outputInterval 1;
       }

I want to exclude the faces on patch that have U.y=-78.how can I write this in expression? is using "?" operator correct? then what should be written after ":" operator?
thanks.