Max-coords-needed

(defun max-coords-needed (piece)
  (loop for dest in piece
     if (keywordp (first dest))
       maximize (reduce #'+ (subseq dest 2) :key #'first) into max-x and
       maximize (reduce #'+ (subseq dest 2) :key #'second) into max-y
     else
       maximize (first dest) into max-x and
       maximize (second dest) into max-y
     finally (return (list max-x max-y))))

; in: DEFUN MAKE-DIAGRAM-ARRAY
;     (LOOP FOR DEST IN PIECE
;           IF (KEYWORDP (FIRST DEST))
;           MAXIMIZE (REDUCE #'+ (SUBSEQ DEST 2) :KEY #'FIRST) INTO MAX-X
;           AND ...)
; --> BLOCK LET SB-LOOP::WITH-MINIMAX-VALUE
; ==>
;   (LET ((MAX-X 0) (#:LOOP-MAXMIN-TEMP-1 0) (#:LOOP-MAXMIN-FLAG-2 NIL))
;     (DECLARE (TYPE REAL MAX-X #:LOOP-MAXMIN-TEMP-1))
;     (SB-LOOP::WITH-MINIMAX-VALUE #S(SB-LOOP::LOOP-MINIMAX
;                                     :ANSWER-VARIABLE MAX-Y
;                                     :TYPE REAL
;                                     :TEMP-VARIABLE #:LOOP-MAXMIN-TEMP-3
;                                     :FLAG-VARIABLE #:LOOP-MAXMIN-FLAG-4
;                                     :OPERATIONS (MAX)
;                                     :INFINITY-DATA NIL)
;       (SB-LOOP::WITH-MINIMAX-VALUE #S(SB-LOOP::LOOP-MINIMAX
;                                       :ANSWER-VARIABLE MAX-X
;                                       :TYPE REAL
;                                       :TEMP-VARIABLE #:LOOP-MAXMIN-TEMP-1
;                                       :FLAG-VARIABLE #:LOOP-MAXMIN-FLAG-2
;                                       :OPERATIONS (MAX)
;                                       :INFINITY-DATA NIL)
;         (SB-LOOP::WITH-MINIMAX-VALUE #S(SB-LOOP::LOOP-MINIMAX
;                                         :ANSWER-VARIABLE MAX-Y
;                                         :TYPE REAL
;                                         :TEMP-VARIABLE #:LOOP-MAXMIN-TEMP-3
;                                         :FLAG-VARIABLE #:LOOP-MAXMIN-FLAG-4
;                                         :OPERATIONS #
;                                         :INFINITY-DATA NIL)
;           (SB-LOOP::LOOP-BODY NIL # # # #)))))
;
; caught STYLE-WARNING:
;   The variable MAX-X is defined but never used.
;
; caught STYLE-WARNING:
;   The variable #:LOOP-MAXMIN-TEMP-1 is defined but never used.
;
; caught STYLE-WARNING:
;   The variable #:LOOP-MAXMIN-FLAG-2 is defined but never used.

; --> BLOCK LET SB-LOOP::WITH-MINIMAX-VALUE LET
; --> SB-LOOP::WITH-MINIMAX-VALUE
; ==>
;   (LET ((MAX-Y 0) (#:LOOP-MAXMIN-TEMP-3 0) (#:LOOP-MAXMIN-FLAG-4 NIL))
;     (DECLARE (TYPE REAL MAX-Y #:LOOP-MAXMIN-TEMP-3))
;     (SB-LOOP::WITH-MINIMAX-VALUE #S(SB-LOOP::LOOP-MINIMAX
;                                     :ANSWER-VARIABLE MAX-X
;                                     :TYPE REAL
;                                     :TEMP-VARIABLE #:LOOP-MAXMIN-TEMP-1
;                                     :FLAG-VARIABLE #:LOOP-MAXMIN-FLAG-2
;                                     :OPERATIONS (MAX)
;                                     :INFINITY-DATA NIL)
;       (SB-LOOP::WITH-MINIMAX-VALUE #S(SB-LOOP::LOOP-MINIMAX
;                                       :ANSWER-VARIABLE MAX-Y
;                                       :TYPE REAL
;                                       :TEMP-VARIABLE #:LOOP-MAXMIN-TEMP-3
;                                       :FLAG-VARIABLE #:LOOP-MAXMIN-FLAG-4
;                                       :OPERATIONS (MAX)
;                                       :INFINITY-DATA NIL)
;         (SB-LOOP::LOOP-BODY NIL (# # NIL #) (#) (# # NIL #) (#)))))
;
; caught STYLE-WARNING:
;   The variable MAX-Y is defined but never used.
;
; caught STYLE-WARNING:
;   The variable #:LOOP-MAXMIN-TEMP-3 is defined but never used.
;
; caught STYLE-WARNING:
;   The variable #:LOOP-MAXMIN-FLAG-4 is defined but never used.
;
; compilation unit finished
;   caught 6 STYLE-WARNING conditions