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Turing Machine in Logo
Logo code saved from Turtle Art Turing Machine session

<pre>window

comment: functions that implement Turtle Art blocks

to tasetpalette :i :r :g :b :myshade
make "s ((:myshade - 50) / 50)
ifelse lessp :s 0 [
make "s (1 + (:s *0.8))
make "r (:r * :s)
make "g (:g * :s)
make "b (:b * :s)
] [ make "s (:s * 0.9)
make "r (:r + ((99-:r) * :s))
make "g (:g + ((99-:g) * :s))
make "b (:b + ((99-:b) * :s))
] setpalette :i (list :r :g :b)
end


to rgb :myi :mycolors :myshade
make "myr first :mycolors
make "mycolors butfirst :mycolors
make "myg first :mycolors
make "mycolors butfirst :mycolors
make "myb first :mycolors
make "mycolors butfirst :mycolors
tasetpalette :myi :myr :myg :myb :myshade
output :mycolors
end


to processcolor :mycolors :myshade
if emptyp :mycolors [stop]
make "i :i + 1
processcolor (rgb :i :mycolors :myshade) :myshade
end


to tasetshade :shade
make "myshade modulo :shade 200
if greaterp :myshade 99 [make "myshade (199-:myshade)]
make "i 7
make "mycolors :colors
processcolor :mycolors :myshade
end


to tasetpencolor :c
make "color (modulo (round :c) 100)
setpencolor :color + 8
end


make "colors [
99 0 0
99 5 0
99 10 0
99 15 0
99 20 0
99 25 0
99 30 0
99 35 0
99 40 0
99 45 0
99 50 0
99 55 0
99 60 0
99 65 0
99 70 0
99 75 0
99 80 0
99 85 0
99 90 0
99 95 0
99 99 0
90 99 0
80 99 0
70 99 0
60 99 0
50 99 0
40 99 0
30 99 0
20 99 0
10 99 0
0 99 0
0 99 5
0 99 10
0 99 15
0 99 20
0 99 25
0 99 30
0 99 35
0 99 40
0 99 45
0 99 50
0 99 55
0 99 60
0 99 65
0 99 70
0 99 75
0 99 80
0 99 85
0 99 90
0 99 95
0 99 99
0 95 99
0 90 99
0 85 99
0 80 99
0 75 99
0 70 99
0 65 99
0 60 99
0 55 99
0 50 99
0 45 99
0 40 99
0 35 99
0 30 99
0 25 99
0 20 99
0 15 99
0 10 99
0 5 99
0 0 99
5 0 99
10 0 99
15 0 99
20 0 99
25 0 99
30 0 99
35 0 99
40 0 99
45 0 99
50 0 99
55 0 99
60 0 99
65 0 99
70 0 99
75 0 99
80 0 99
85 0 99
90 0 99
95 0 99
99 0 99
99 0 90
99 0 80
99 0 70
99 0 60
99 0 50
99 0 40
99 0 30
99 0 20
99 0 10]
make "shade 50
tasetshade :shade


to tapop
if emptyp :taheap [stop]
make "tmp first :taheap
make "taheap butfirst :taheap
output :tmp
end


to taminus :y :x
output sum :x minus :y
end


to tasetxy :x :y
setxy :x :y
end


comment: Turing Machine procedures


to turtleblocks_0
comment: Comment
#sTuring_Machine
end


to start
comment: main program
comment: Creates and initializes necessary variables, writes program block, writes tape, runs program
clean #sSetup #sProgram #sTape #sExecute
end


to #sSetup
comment: Create variables, set initial values
right 90.0
setpensize 25.0
tasetpencolor 0.0
tasetshade 50.0 penup
make "#scell 0.0
make "#ssymbol 0.0
make "#smove 0.0
make "#sstate 1.0
make "#sleftedge -390.0
make "#stapey 290.0
make "#sprogramy 200.0
make "#scellwidth 25.0
make "#sright 1.0
make "#shalt 4.0
make "#sA 3.0
make "#sB 2.0
end


to #sTape
comment: Write initial tape. User can change values in repeat statements to change arguments.
#sToTape
pendown
tasetpencolor 20.0
repeat #sA [ #sWriteCell ]
tasetpencolor 0.0
#sWriteCell
tasetpencolor 20.0
repeat #sB [ #sWriteCell ]
tasetpencolor 0.0
#sWriteCell #sToTape penup
end


to #sProgram
comment: Write program table
tasetxy :#sleftedge :#sprogramy
tasetpencolor 20.0
#sWriteCell
tasetpencolor 20.0
#sWriteCell
tasetpencolor 40.0
#sWriteCell
tasetxy :#sleftedge taminus ycor :#scellwidth
tasetpencolor 20.0
#sWriteCell
tasetpencolor 20.0
#sWriteCell
tasetpencolor 20.0
#sWriteCell
tasetxy :#sleftedge taminus ycor :#scellwidth
tasetpencolor 0.0
#sWriteCell
tasetpencolor 0.0
#sWriteCell
tasetpencolor 60.0
#sWriteCell
stack1
end

to stack1
comment: Continuation of Program so that the segments fit on the Turtle Art screen
tasetxy :#sleftedge taminus ycor :#scellwidth
tasetpencolor 20.0
#sWriteCell
tasetpencolor 20.0
#sWriteCell
tasetpencolor 40.0
#sWriteCell
tasetxy :#sleftedge taminus ycor :#scellwidth
tasetpencolor 0.0
#sWriteCell
tasetpencolor 20.0
#sWriteCell
tasetpencolor 80.0
#sWriteCell
tasetxy
:#sleftedge taminus ycor
:#scellwidth
tasetpencolor 0.0
#sWriteCell
tasetpencolor 20.0
#sWriteCell
tasetpencolor 80.0
#sWriteCell
penup
end


to #sExecute

comment: Test for halt or next program step
make "#sstep 0.0
forever
[ ifelse ( equal? :#sstate :#shalt )
[ stop ]
[ #sReadPixel
#sSetValue
make "#ssymbol :#sValue
#sToProgram
wait 1.0
#sSetSymbol
forward :#scellwidth
#sSetMove
forward :#scellwidth
#sSetState
#sLog
#sToTape
#sWriteSymbol
#sNewCell
wait 1.0
make "#sstep sum :#sstep 1.0 ] ]
end


to #sToTape
comment: Move turtle to current cell on tape
tasetxy
sum :#sleftedge product :#scellwidth :#scell
:#stapey
end


to #sToProgram
comment: Move Turtle to beginning of current program row to execute
tasetxy
taminus :#sleftedge 3.0
taminus :#sprogramy product :#scellwidth sum :#ssymbol product 2.0 taminus :#sstate 1.0
end


to #sWriteCell

comment: Write current color to current cell, and move to next cell
pendown
forward 0.0
penup
forward :#scellwidth
end


to #sWriteSymbol
comment: Write current color in cell without moving
pendown
forward 0.0
penup
end


to #sReadPixel

comment: Read RGB values of pixel to stack, pop to variables
keyboard
make "#sR tapop
make "#sG tapop
make "#sB tapop
end


to #sSetValue
comment: Find value of cell symbol from RGB numbers
ifelse not ( equal? :#sB 128.0 )
[ ifelse not ( equal? :#sR 128.0 )
[ ifelse not ( equal? :#sG 128.0 )
[ ifelse ( equal? :#sG 0.0 )
[ make "#sValue 0.0 ]
[ make "#sValue 1.0 ] ]
[ make "#sValue 3.0 ] ]
[ make "#sValue 4.0 ] ]
[ make "#sValue 2.0 ]
end


to #sSetMove
comment: Read next Move direction from program table
#sReadPixel
#sSetValue
make "#smove :#sValue
end


to #sSetSymbol
comment: Read next Symbol to write from program table
#sReadPixel
#sSetValue
make "#ssymbol :#sValue
ifelse ( equal? :#ssymbol 0.0 )
[ tasetpencolor 0 ]
[ tasetpencolor 20.0 ]
end


to #sSetState
comment: Read next State from program table
#sReadPixel
#sSetValue
make "#sstate :#sValue
end


to #sNewCell
comment: Move left or right and set cell number of new location
ifelse ( equal? :#smove :#sright )
[ forward :#scellwidth
make "#scell sum :#scell 1.0 ]
[ back :#scellwidth
make "#scell taminus :#scell 1.0 ]
end


to #sLog
comment: Write Step number, Symbol, Move, State, Cell number on new log line in black, saving and restoring
comment: current position and current color
make "#sx xcor
make "#sy ycor
tasetxy -300.0 taminus 200.0 product 20.0 :#sstep
make "#scolor pencolor
tasetpencolor 0
label sentence ('box', "427)
#sstep
forward 30.0
label sentence ('box', "339)
#ssymbol
forward 20.0
label sentence ('box', "341)
#smove
forward 20.0
label sentence ('box', "537)
#sstate
forward 20.0
label sentence ('box', "562)
#scell
tasetpencolor :#scolor
end
</pre>
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