question: public boolean isValid ( ) { return ( Math . abs ( lo ( ) ) <= S2 . M_PI && Math . abs ( hi ( ) ) <= S2 . M_PI && ! ( lo ( ) == - S2 . M_PI && hi ( ) != S2 . M_PI ) && ! ( hi ( ) == - S2 . M_PI && lo ( ) != S2 . M_PI ) ) ; }
target:  An interval is valid if neither bound exceeds Pi in absolute value, and the value -Pi appears only in the Empty() and Full() intervals.