; general information
;
; file:   dobby.l of wfr of gp of clos of lisp of ai
; type:   pcl (clos)
; line:   named after Dobby, as in Harry Potter #2
; assign: number 1
; date:   Sept 9, 1999
;
; elaboration:
;
;   A program which toys with a little creature, a robot
;   we will call Dobby -- after Dobby in "Harry  Potter
;   and the Chamber of Secrets" who was constanly banging
;   his head into the wall.
;
;----------------------------------------------------------
;  Enter "clos"

  ( in-package "PCL" )

;----------------------------------------------------------
;  Define a position class to represent a position in 
;  Dobby's world.

  ( defclass position ()
    (  ( row :accessor position-row :initarg :row :initform 0 )
       ( col :accessor position-col :initarg :col :initform 0 )
    )
  )

  ( defmethod display ( ( p position ) )
    ( princ "(" )
    ( princ ( position-row p ) )
    ( princ "," )
    ( princ ( position-col p ) )
    ( princ ")" )
    ( terpri )
  )

;-------------------------------------------------------
;  Define a method called FREE which returns YES if the position
;  given by row and column values is free for Dobby to move in to, 
;  NO if it is not -- assuming Dobby is not interested in moving
;  nowhere

  ( defmethod free ( ( row number ) ( col number) )
    ( cond
      ( ( < row 1 ) 'no )
      ( ( < col 1 ) 'no )
      ( ( > row 8 ) 'no )
      ( ( > col 8 ) 'no )
      ( ( and ( = row 7 ) ( = col 4 ) ) 'no )
      ( ( and ( = row 7 ) ( = col 5 ) ) 'no )
      ( ( and ( = row 8 ) ( = col 4 ) ) 'no )
      ( ( and ( = row 8 ) ( = col 5 ) ) 'no )
      ( t 'yes )
    )
  )

;------------------------------------------------------------
;  Define a method to place Dobby somewhere in his world.

  ( defmethod place ( ( row number ) ( col number ) )
    ( setf *location*
           (make-instance 'position :row row :col col )
    )
  )
;-----------------------------------------------------------
;  Define a method to move Dobby north -- presuming the cell to
;  the north is free

  ( defmethod north ()
    ( setf ( position-row *location* )
           ( - ( position-row *location* ) 1 ) 
    )
    ( prin1 'north ) ( terpri )
  )

;---------------------------------------------------------
;  Define a method to move Dobby south -- presuming the cell to
;  the south is free

  ( defmethod south ()
    ( setf ( position-row *location* )
           ( + ( position-row *location* ) 1 )
    )
    ( prin1 'south ) ( terpri )
  )

;--------------------------------------------------------------- 
;  Define a method to move Dobby east -- presuming the cell to
;  the east is free

  ( defmethod east ()
    ( setf ( position-col *location* )
           ( + ( position-col *location* ) 1 )
    )
    ( prin1 'east ) ( terpri )
  )

;------------------------------------------------------------------
;  Define a method to move Dobby west -- presuming the cell to 
;  the west is free

  ( defmethod west ()
    ( setf ( position-col *location* )
           ( - ( position-col *location* ) 1 )
    )
    ( prin1 'west ) ( terpri )
  )

;--------------------------------------------------------------------- 
;  Define a method called n which returns 0 if the cell to the
;  north of Dobby is free, 1 if it is not free.

  ( defmethod n ()
    ( setf row ( - ( position-row *location* ) 1 ) )
    ( setf col ( position-col *location* ) )
    ( if ( eq ( free row col ) 'yes )
      nil
      t
    )
  )
 
;---------------------------------------------------------------------
;  Define a method called ne which returns 0 if the cell to the
;  north-east of Dobby is free, 1 if it is not free.

  ( defmethod ne ()
    ( setf row ( - ( position-row *location* ) 1 ) )
    ( setf col ( + ( position-col *location* ) 1 ) )
    ( if ( eq ( free row col ) 'yes )
      nil
      t
    )
  )

;-------------------------------------------------------------------
;  Define a method called e which returns 0 if the cell to the
;  east of Dobby is free, 1 if it is not free.

  ( defmethod e ()
    ( setf row ( position-row *location* ) )
    ( setf col ( + ( position-col *location* ) 1 ) )
    ( if ( eq ( free row col ) 'yes )
      nil
      t
    )
  )
;--------------------------------------------------------------------
;  Define a method called se which returns 0 if the cell to the
;  south-east of Dobby is free, 1 if it is not free.

  ( defmethod se ()
    ( setf row ( + ( position-row *location* ) 1 ) )
    ( setf col ( + ( position-col *location* ) 1 ) )
    ( if ( eq ( free row col ) 'yes )
      nil 
      t
    )
  )

;-------------------------------------------------------------------- 
;  Define a method called s which returns 0 if the cell to the
;  south of Dobby is free, 1 if it is not free.

  ( defmethod s ()
    ( setf row ( + ( position-row *location* ) 1 ) )
    ( setf col ( position-col *location* ) )
    ( if ( eq ( free row col ) 'yes )
      nil
      t
    )
  )

;---------------------------------------------------------------------
;  Define a method called sw which returns 0 if the cell to the
;  south-west of Dobby is free, 1 if it is not free.

  ( defmethod sw ()
    ( setf row ( + ( position-row *location* ) 1 ) )
    ( setf col ( - ( position-col *location* ) 1 ) )
    ( if ( eq ( free row col ) 'yes )
      nil 
      t
    )
  )

;---------------------------------------------------------------------
;  Define a method called w which returns 0 if the cell to the
;  west of Dobby is free, 1 if it is not free.

  ( defmethod w ()
    ( setf row ( position-row *location* ) )
    ( setf col ( - ( position-col *location* ) 1 ) )
    ( if ( eq ( free row col ) 'yes )
      nil
      t
    )
  )

;----------------------------------------------------------------------
;  Define a method called nw which returns 0 if the cell to the
;  north-west of Dobby is free, 1 if it is not free.

  ( defmethod nw ()
    ( setf row ( - ( position-row *location* ) 1 ) )
    ( setf col ( - ( position-col *location* ) 1 ) )
    ( if ( eq ( free row col ) 'yes )
      nil
      t
    )
  )

;-----------------------------------------------------------------------
;  Define a method called move which will cause Dobby to take a step in
;  one of four directions -- north, south, east, or west.

  ( defmethod move ()
    ( if ( and ( or (n) (ne) ) ( not (e) ) )
         (east)
         ( if ( and ( or (e) (se) ) ( not (s) ) )
              (south)
              ( if ( and ( or (s) (sw) ) ( not (w) )) 
                   (west)
                   (north)
              )
         )
     )
  )