public static Expression nanIf(Expression expression1, Expression expression2) {
        return x("NANIF(" + expression1.toString() + ", " + expression2.toString() + ")");
    }
public static Expression nanIf ( Expression expression1 , Expression expression2 ) { return x ( "NANIF(" + expression1 . toString ( ) + ", " + expression2 . toString ( ) + ")" ) ; }
Returned expression results in NaN if expression1 = expression2, otherwise returns expression1.
Returns MISSING or NULL if either input is MISSING or NULL.