- [f == file_of(ksq) && rkThem == relative_rank(Us, ksq) + 1 ? BlockedByKing :
- rkUs == RANK_1 ? Unopposed :
- rkThem == rkUs + 1 ? BlockedByPawn : Unblocked]
+ [(shift<Down>(b) & ksq) ? BlockedByKing :
+ rkUs == RANK_1 ? Unopposed :
+ rkThem == (rkUs + 1) ? BlockedByPawn : Unblocked]