+/// squares_aligned returns true if the squares s1, s2 and s3 are aligned
+/// either on a straight or on a diagonal line.
+
+inline bool squares_aligned(Square s1, Square s2, Square s3) {
+ return (BetweenBB[s1][s2] | BetweenBB[s1][s3] | BetweenBB[s2][s3])
+ & ((1ULL << s1) | (1ULL << s2) | (1ULL << s3));
+}
+
+