Little endian rank-file (LERF) mapping implies following C++ enumeration:
enum enumSquare {
a1, b1, c1, d1, e1, f1, g1, h1,
a2, b2, c2, d2, e2, f2, g2, h2,
a3, b3, c3, d3, e3, f3, g3, h3,
a4, b4, c4, d4, e4, f4, g4, h4,
a5, b5, c5, d5, e5, f5, g5, h5,
a6, b6, c6, d6, e6, f6, g6, h6,
a7, b7, c7, d7, e7, f7, g7, h7,
a8, b8, c8, d8, e8, f8, g8, h8
};We rely on the compass rose to identify ray-directions with following increments to neighbored squares.
noWe nort noEa
+7 +8 +9
\ | /
west -1 <- 0 -> +1 east
/ | \
-9 -8 -7
soWe sout soEa
a-file 0x0101010101010101
h-file 0x8080808080808080
1st rank 0x00000000000000FF
8th rank 0xFF00000000000000
a1-h8 diagonal 0x8040201008040201
h1-a8 antidiagonal 0x0102040810204080
light squares 0x55AA55AA55AA55AA
dark squares 0xAA55AA55AA55AA55
From: https://www.chessprogramming.org/Square_Mapping_Considerations#Endianness