     }
 
     /// Shifts the bits of `self` once toward `direction`.
-    public mutating func shiftOnce(toward direction: ShiftDirection) {
-        self = shiftedOnce(toward: direction)
+    public mutating func shift(toward direction: ShiftDirection) {
+        self = shifted(toward: direction)
     }
 
     /// Returns the bits of `self` filled toward `direction` blocked by `blockers`.

    }

    /// Returns the bits of `self` shifted once toward `direction`.
    @warn_unused_result(mutable_variant="shiftOnce")
    public func shiftedOnce(toward direction: ShiftDirection) -> Bitboard {
        switch direction {
        case .North:     return  self << 8
        case .South:     return  self >> 8


    /// Returns the attacks available to the king in `self`.
    internal func _kingAttacks() -> Bitboard {
        let attacks = shifted(toward: .East) | shifted(toward: .West)
        let bitboard = self | attacks
        return attacks
            | bitboard.shifted(toward: .North)
            | bitboard.shifted(toward: .South)
    }

    /// Returns the attacks available to the knight in `self`.
