sub bandpass {
    my( $aref, $loValue, $hiValue ) = @_;
    return if $loValue > $aref->[-1] or $hiValue < $aref->[0];
    my( $lo, $hi ) = ( 0, $#{ $aref } );
    while( $lo < $hi ) {
        my $mid = int( ( $lo + $hi ) / 2 );
        if( $aref->[ $mid ] >= $loValue and $aref->[ $mid ] <= $hiValue ) {
            $lo = $hi = $mid;
            last;
        }
        elsif( $aref->[ $mid ] < $loValue ) {
            $lo = $mid + 1;
        }
        elsif( $aref->[ $mid ] > $hiValue ) {
            $hi = $mid - 1;
        }
    }
    return if $loValue > $aref->[ $hi ] or $hiValue < $aref->[ $lo ];
    --$lo while $lo and $aref->[ $lo - 1 ] >= $loValue;
    ++$hi while $hi < $#{ $aref } and $aref->[ $hi + 1 ] <= $hiValue;
    return @{ $aref }[ $lo .. $hi ];
}