question: public double [ ] estimateL2DistanceSquared ( Datum queryDatum ) { RealVector vector = queryDatum . metrics ( ) ; double [ ] estimates = new double [ 2 ] ; for ( int i = 0 ; i < k ; i ++ ) { double deltaLo = vector . getEntry ( i ) - this . boundaries [ i ] [ 0 ] ; double deltaHi = this . boundaries [ i ] [ 1 ] - vector . getEntry ( i ) ; double sqDeltaLo = deltaLo * deltaLo ; double sqDeltaHi = deltaHi * deltaHi ; if ( deltaLo < 0 || deltaHi < 0 ) { if ( sqDeltaHi < sqDeltaLo ) { estimates [ 0 ] += sqDeltaHi ; estimates [ 1 ] += sqDeltaLo ; } else { estimates [ 0 ] += sqDeltaLo ; estimates [ 1 ] += sqDeltaHi ; } } else { estimates [ 1 ] += Math . max ( sqDeltaHi , sqDeltaLo ) ; } } return estimates ; }
target:  Estimates bounds on the distance to a region