logred.red

Red [needs: view]

turtle: #()

win: layout [ tfield: base 500x500 white draw [] 
              panel [
                text "History" return history: text-list 180x350 data [] return 
                panel [ button "Save" [save request-file history/data]
                        button "Load" [commands: load request-file foreach cmd commands [process-cmd cmd]] ]
              ]
              return
              text "Command" cmdfield: field 300x25 [process-cmd cmdfield/text] 
              error: text 100x25 ]
              
home: func[] [
  turtle/position:  250x250
  turtle/color:     black
  turtle/direction: 0
  turtle/pen-down:  true
]

reset: func[] [
  clear history/data
  clear tfield/draw
  home
]

turn-by: func[degrees [integer!]] [
  turtle/direction: turtle/direction + degrees // 360
]

move-by: func[distance [integer!]] [
  delta: make pair! compose [(to integer! (sine turtle/direction) * distance) (to integer! (cosine turtle/direction) * distance)]
  if turtle/pen-down [append/only tfield/draw compose [line (translate-loc turtle/position) (translate-loc turtle/position + delta)]]
  turtle/position: turtle/position + delta
]

translate-loc: func [loc [pair!]] [loc/y: 500 - loc/y loc]

set-color: func [color] [
  append/only tfield/draw compose [pen (color)]
]

draw-turtle: func[] [
  headpos: make pair! compose [(to integer! (sine turtle/direction) * 10) (to integer! (cosine turtle/direction) * 10)]
  append/only tfield/draw compose [fill-pen green circle (translate-loc turtle/position) 10 
    circle (translate-loc turtle/position + headpos) 3 fill-pen off]
]

turtle-repeat: func [cnt rblk] [
  repeat none! cnt [parse rblk parse-rules]
]

parse-rules: [
  some [
    ['fd | 'forward] set distance integer! (move-by distance) |
    ['bk | 'back] set distance integer! (move-by distance * -1) |
    'right set degrees integer! (turn-by degrees) |
    'left set degrees integer! (turn-by degrees * -1) |
    ['pu | 'penup] (turtle/pen-down: false) |
    ['pd | 'pendown] (turtle/pen-down: true) |    
    'color set value word! (set-color value) |
    'repeat set value integer! set blk block! (turtle-repeat value blk) |
    'reset (reset) |
    'home (home) |
    'quit (quit) |
    set word word! (error/text: mold/only compose [Unknown Word (word)]) break 
  ]
]

process-cmd: func[cmd [string!]] [
  remove back tail tfield/draw
  error/text: ""
  parse load/all cmd parse-rules
  if empty? error/text [append history/data cmd cmdfield/text: none ]
  draw-turtle  
]

process-cmd "home"

view/no-wait win

I think that in turtle-repeat, the code repeat none! can be replaced by loop.