0001 #define sib(i) ( 1 + ( ( (i) - 1 ) ^ 0x01 ) ) // ( (i) & 1 ? (i) + 1 : (i) - 1 ) //sibling
0002 #define lc(i)  ( 1 + ( ( i ) << 1 ) ) //left child
0003 #define rc(i)  ( ( 1 + ( i ) ) << 1 ) //right child
0004 #define ln(i)  ( lc( sib( i ) ) ) //left nephew
0005 #define rn(i)  ( rc( sib( i ) ) ) //right nephew
0006 #define isLC(i)   ( ( 0 < (i) ) && (     1 & (i)   ) ) //left child
0007 #define isRC(i)   ( ( 0 < (i) ) && ( ! ( 1 & (i) ) ) ) //right child
0008 #define hasGP(i)  ( 2 < (i) ) //having grandparent
0009 #define gp(i)  ( ( (i) - 3 ) >> 2 ) //grandparent
0010 #define lp(i)  ( lc( gp( i ) ) ) //left parent = the left child of grandparent
0011 #define rp(i)  ( rc( gp( i ) ) ) //right parent = the right child of grandparent