Piece

(defun directionp (thing)
  (member thing *all-dirs*))

(defun piece-function (x y)
  #'(lambda (&rest dirs-and-signatures)
      (make-piece x y
                  (remove-if-not #'directionp dirs-and-signatures)
                  (remove-if #'directionp dirs-and-signatures))))

(defparameter *atoms*
  '((:wazir 1 0)
    (:ferz 1 1)
    (:dabbabah 2 0)
    (:knight 2 1)
    (:alfil 2 2)
    (:threeleaper 3 0)
    (:camel 3 1)
    (:zebra 3 2)
    (:tripper 3 3)
    (:fourleaper 4 0)
    (:giraffe 4 1)
    (:doubleknight 4 2)
    (:antelope 4 3))
  "List that holds definitions for all chess pieces.")

(defparameter *piece-functions*
  (let ((hash-table (make-hash-table)))
    (dolist (piece *atoms* hash-table)
      (destructuring-bind (piece-name x y) piece
        (setf (gethash piece-name hash-table) (piece-function x y))))
    hash-table)
  "Hash table that holds lambdas for all chess pieces.")

(defun piece (name &rest dirs-and-signatures)
  "Creates a simple chess piece based on its name argument.
The names of the basic items or a two-number list is accepted.
Additionally, a single number n is interpreted as the combination of '(n n) and '(n 0)."
    (cond ((member name *atoms* :key #'first)
           (apply (gethash name *piece-functions*) dirs-and-signatures))
          ((numberp name)
           (append (apply (piece-function name 0) dirs-and-signatures)
                   (apply (piece-function name name) dirs-and-signatures)))
          (t (piece-function (first name) (second name)))))