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Penrose Tiling
A famous non-repeating tiling pattern, invented (discovered.) by Roger Penrose, a giant in the worlds of mathematics and floor-coverings.
The following logo program produces a penrose tiling. I found this at http://logo.twentygototen.org/E3_yJcQ4.
I haven't looked through it enough to understand it. I can only marvel at its wondrousness.
;; PENROSE TILING IN LOGO ;;
; Now with comments and constants, granted from
; actually looking at the syntax. Feel free to
; poke around.
;;;;;;;;;;;;;;;
;; CONSTANTS ;;
;;;;;;;;;;;;;;;
; Brush constants
make "kite_col [220 25 20]
make "dart_col [12 12 20]
make "pwidth 2
; Shape constants
make "startx 20
make "starty 480
make "size 10
make "detail 9
; Golden ratio
make "phi     1.61803399 
make "phi_inv 0.61803399
;;;;;;;;;;;;;;;;;
;; SUBROUTINES ;;
;;;;;;;;;;;;;;;;;
;; DRAW A HALF-KITE, WITH DEFLATION ;;
to hkite :depth :dir  
  ifelse :depth > 1 
  [ ; Deflation case
    ; reduce recursion depth
    make "depth  :depth-1
    ; Draw components and return to origin
    turn :dir 36
    hdart :depth (not :dir)
    turn (not :dir) 36
    fw (power :phi :depth) * :size
    rt 180
    hkite :depth (not :dir)
    turn (not :dir) 72
    hkite :depth :dir
    turn :dir 72
    fw (power :phi :depth) * :size
    rt 180
  ]  
  [ ; Base case
    ; Draw half kite and return to origin
    pd
    color :kite_col
    fw :size
    turn :dir 108
    fw :size*:phi_inv
    pu
    turn :dir 108
    fw :size
    turn :dir 144
  ]
end        
;; DRAW A HALF-DART, WITH DEFLATION ;;
to hdart :depth :dir
  ifelse :depth > 1 
  [ ; Deflation case
    ; reduce recursion depth
    make "depth :depth - 1
    ; Draw components and return to origin
    hkite :depth :dir
    fw (power :phi :depth) * :size
    turn :dir 144
    hdart :depth :dir
    turn :dir 36
    fw (power :phi :depth) * :size
    rt 180
  ]
  [ ; Base case
    ; Draw a half-dart
    pd
    color :dart_col
    fw :size
    turn :dir 144
    fw :size*:phi_inv
    pu
    turn :dir 72
    fw :size*:phi_inv
    turn :dir 144
  ]
end
;; PARAMETRISED RT/LT ;;
to turn :dir :angle
  ifelse :dir [rt :angle] [lt :angle]
end
;;;;;;;;;;;;;;;;;;
;; MAIN PROGRAM ;;
;;;;;;;;;;;;;;;;;;
reset
; Initialize
setxy :startx :starty
penwidth :pwidth
; Draw a single kite, deflating as required
hkite :detail true
rt 72
hkite :detail false