TO MOTIF SIZE
   ; DRAW AN ASYMETRIC PATTERN.
   FORWARD :SIZE
   RIGHT 90
   FORWARD :SIZE/2
   BACK :SIZE/2
   LEFT 90
   BACK :SIZE
END

TO REVERSEMOTIF SIZE
   ; DRAW THE MIRROR IMAGE OF THE PATTERN DRAWN BY PROCEDURE MOTIF.
   ; THIS IS DONE BY SWAPPING THE COMMANDS "LEFT" AND "RIGHT".
   FORWARD :SIZE
   LEFT 90
   FORWARD :SIZE/2
   BACK :SIZE/2
   RIGHT 90
   BACK :SIZE
END

TO INFCROSS SIZE NUMREPS
   ; DRAW A FRIEZE PATTERN WITH SYMMETRY TYPE (BLUE) INFINITY (RED) CROSS.

   ; START WITH THE PEN DOWN.
   PENDOWN

   REPEAT :NUMREPS [

      ; DRAW THE MOTIF.
      MOTIF :SIZE

      ; MOVE FORWARD AND LEAVE THE TURTLE FACING DOWN.
      PENUP
      RIGHT 90 
      FORWARD :SIZE 
      RIGHT 90
      PENDOWN

      ; DRAW THE MIRROR IMAGE MOTIF (POINTING DOWN).
      REVERSEMOTIF :SIZE

      ; MOVE FORWARD AND LEAVE THE TURTLE FACING UP.
      PENUP
      LEFT 90 
      FORWARD :SIZE 
      LEFT 90
      PENDOWN 
   ]
END

TO INFINF SIZE NUMREPS
   ; DRAW A FRIEZE PATTERN WITH SYMMETRY TYPE (BLUE) INFINITY INFINITY.

   ; START WITH THE PEN DOWN
   PENDOWN

   REPEAT :NUMREPS [

      ; DRAW THE MOTIF. 
      MOTIF :SIZE

      ; MOVE FORWARD (DOUBLE STEP) AND LEAVE THE TURTLE FACING UP.
      PENUP 
      RIGHT 90 
      FORWARD 2*:SIZE 
      LEFT 90 
      PENDOWN
   ]
END

TO QUIZ4
   ; EXAMPLE OF PART OF A PROGRAM FOR ASSIGNMENT QUIZ 4

   CLEARSCREEN

   ; DRAW PATTERN (BLUE) INFINITY INFINITY.
   INFINF 10 34

   ; RETURN TO THE CENTER OF THE SCREEN THEN MOVE UP.
   PENUP
   HOME 
   FORWARD 50 
   PENDOWN

   ; DRAW PATTERN (BLUE) INFINITY (RED) CROSS.
   INFCROSS 10 34
END

TO LOADFILE
   ; USE THIS PROCEDURE TO QUICKLY LOAD NEW VERSIONS OF THE LOGO CODE.
   LOAD "W:/FRIEZES.TXT
END