; Hamming Distance Simulation
; written by Crystal Barchet and Teresa Carrigan, 2004


globals [ praise myDigits current-a small-ham current-b here-y start-yg start-xg start-x 
          newX bit-pattern-list number x y step doneyet? ]
patches-own [ name ] 
breeds [ place place2 arrow ]
place-own [ place-name ]
place2-own [ place-name ]
arrow-own [ state ] 


;runs setup when program is first loaded
to startup
  setup
end

;initializes variables
to setup
  locals [ bit-pattern offset start-y ]
  ca
  set praise ["You got it!" "Correct!" "Awesome!" "Perfect!" "Right!" "Bravo!" "Splendid!"]
  set myDigits [ "0" "1" ]
  set bit-pattern-list [ ]
  set number 0
  set here-y 6
  set start-y 5
  set offset 1
  set start-x 9.26
  set start-xg 9.26
  set start-yg 6
  set current-a 0
  set current-b 1
  set doneyet? false
  set small-ham 100
  set x 0
  set y 0
    
 
 
; create explanation bars at top and bottom
    ask patches with [ pycor < -5 ]
        [ set pcolor blue ]
    ask patch-at 5 -6
      [ set plabel "Hamming Distance" 
        set plabel-color white
        set name -1
      ]
     ask patch-at 5 -7
       [
         set plabel ""
         set plabel-color white
         set name -2
       ]
      ask patch-at -10 5
       [
         set plabel 0
         set plabel-color yellow
       ] 
       ask patch-at -10 4
       [
         set plabel 1
         set plabel-color yellow
       ] 
       ask patch-at -10 3
       [
         set plabel 2
         set plabel-color yellow
       ] 
       ask patch-at -10 2
       [
         set plabel 3
         set plabel-color yellow
       ] 

  repeat 4
    [
        ; create the set of bit patterns

         ask patch-at -4 start-y
             [  set bit-pattern ""
                repeat number-of-digits
                    [
                          set bit-pattern (word bit-pattern random-one-of myDigits)
                    ]
                set plabel bit-pattern
                set plabel-color yellow
                set bit-pattern-list lput bit-pattern bit-pattern-list
              ]
         set start-y start-y - offset

     ]    


    explain -1 "Hamming Distance"
    set step 0
    set doneyet? false
    
end




to explain [ which what ]
  ask patches with [ name = which ]
    [  set plabel what ]
end

to process-two [ a b ]
  locals [ a-value b-value here-x ham-dist]
  set ham-dist 0
  pick-two a b
  ;  now run the arrow
 ; creates the red arrow
 cct-arrow 1 [
    set heading -180
    set color red
    set shape "arrow"
    set label-color white
    setxy start-xg start-yg
    set start-x 9.26
    set newX start-x - 1
  ] 
  
; makes the arrow go through each pair of numbers  
repeat number-of-digits
[   

  ask arrow
  [ 
     set state "empty"
     set a-value 0
     set b-value 0
     set here-x xcor
     repeat 4 [
        showturtle
        fd 1
        if any? other-turtles-here
          [  ifelse state = "empty"
               [ set a-value label-of random-one-of other-turtles-here 
                 set state "first"
               ]
               [ set b-value label-of random-one-of other-turtles-here 
                 set state "second"
                 if a-value != b-value
                   [  ask other-turtles-here
                         [ set label-color red ]
                      set ham-dist ham-dist + 1
                   ]
               ]
          ]
        wait slow-motion
        ]
       hideturtle
       setxy start-x - 1 here-y
       set newX start-x - 1
       set start-x newX

   ]
]

  ifelse ham-dist <= small-ham
    [
      set small-ham ham-dist
    ]
    [
      set small-ham small-ham
    ]

  explain -1 "Hamming distance of this pair is " + ham-dist
  explain -2 "Smallest Hamming distance so far is " + small-ham
  
  
end


;  do a single step (whichever comes next)
to one-step
  if  not doneyet? 
    [
      process-two current-a current-b
      set current-b current-b + 1
      if current-b > 3
        [
          set current-a current-a + 1
          set current-b current-a + 1
            if current-a >= 3
              [
                set doneyet? true
                finish-up
              ]
        ]
    ]

end



; compare the two bit patterns
to pick-two [ a b ]

ask turtles [ die ]
explain -1 "Compare bit patterns " + a + " and " + b

; this is the "spot" where the first pattern wanders to
cct-place 1 [
          setxy -4 (5 - a)
          set label item a bit-pattern-list
          set shape "circle"
          set color black
          set label-color cyan
          set size 0
          set place-name "moving"
          hideturtle
          ]

; this is the "spot" where the second pattern wanders to
cct-place2 1 [
          setxy -4 (5 - b)
          set label item b bit-pattern-list
          set shape "circle"
          set color black
          set label-color cyan
          set size 0
          set place-name "moving"
          hideturtle
          ]

; moves the first bit pattern to its spot
ask place with [ place-name = "moving" ]
          [ 
            wander a 1
          ]
   wait slow-motion

ask place [ die ]

; moves the second bit pattern to its spot   
ask place2 with [ place-name = "moving" ]
          [
            wander b 2 
          ]
ask place2 [ die ]

  set step step + 1
end


  ; this method makes the first item to be compared to move to a new position
to wander [ source dest ]
  locals [ to-x to-y n offset newNum1]
  ifelse dest = 1
    [  set to-x 5
       set to-y 5
    ]
    [  set to-x 5
       set to-y 4
    ]
  set offset 1
  showturtle
  if any? place with [ place-name != "moving" ]
    [
      set to-x xcor-of min-one-of place with [ place-name != "moving"] [ xcor ]
      set to-x (to-x - 1.5)
    ]
  while [ (ycor != to-y) or (xcor != to-x) ]
    [
      set heading towardsxy-nowrap to-x to-y
      set n (distancexy to-x to-y)
      ifelse n > 1
        [ fd 1 ] 
        [ setxy to-x to-y ]
      wait slow-motion / 2   
    ]
    
  set place-name "done"
  set label ""      
  set newNum1 item source bit-pattern-list
          
  ask patch-at 5 0 
  [
    repeat number-of-digits
    [
      sprout 1 
      [
         set shape "box"
         set color black
         set label last newNum1
         set size 0
         set label-color cyan
         set heading -90
         fd offset
         set offset offset + 1     
      ]
        set newNum1 but-last newNum1
    ]
  ]

end


;  do all remaining steps, called by a forever button
to go
  ifelse  not doneyet? 
    [  
      one-step
    ]
    [  
       stop
    ]
end

;  last messsages
to finish-up
  locals [ detect correct ]
  explain -1 "The smallest Hamming distance was " + small-ham 
  explain -2 "so the Hamming distance of the set is " + small-ham
  if slow-motion > 0
    [  wait 2  ]
  set detect small-ham - 1
  set correct int ( detect / 2 )
  explain -1 "Hamming distance of set = " + small-ham + " so the set can"
  explain -2 "detect " + detect + " errors and correct " + correct + "."
  
  if small-ham < 1
    [  explain -1 "Hamming distance of set = " + small-ham 
       explain -2 "so this set cannot be used; there is a duplicate code."
    ]
end



;  start same example again
to show-again

  locals [ bit-pattern offset start-y ]
  set number 0
  set here-y 6
  set start-y 5
  set offset 1
  set start-x 9.26
  set start-xg 9.26
  set start-yg 6
  set current-a 0
  set current-b 1
  set doneyet? false
  set small-ham 100
  set x 0
  set y 0
  ask turtles
    [
      die
    ]
end



to ask-other 
  locals [ guess target question ]
  set guess user-input ( "What is the hamming distance of the problem shown?" )
  set guess read-from-string guess
  while [ not doneyet? ]
    [
       go
    ]
  finish-up
  set target small-ham
  ifelse guess = target 
    [ user-message random-one-of praise ]
    [ user-message "I'm sorry, but the correct hamming distance is " +  target]
end




;  ask a quiz question
to quiz
  locals [ save-slow ]
  without-interruption [ setup ]
  set save-slow slow-motion
  set slow-motion 0
  wait .5
  ask-other
  set slow-motion save-slow
end



; *** NetLogo Model Copyright Notice ***
;
; Copyright 2004 by Crystal R. Barchet and Teresa Carrigan.  All rights reserved.
;
; Permission to use, modify or redistribute this model is hereby granted,
; provided that both of the following requirements are followed:
; a) this copyright notice is included.
; b) this model will not be redistributed for profit without permission
;    from Teresa Carrigan.
; Contact Teresa Carrigan for appropriate licenses for redistribution 
; for profit.
;
; To refer to this model in academic publications, please use:
; Barchet, C. and Carrigan, T. (2004).  Hamming Distance Simulation
; Blackburn College, Carlinville, IL.
;
; In other publications, please use:
; Copyright 2004 by Crystal R. Barchet and Teresa W. Carrigan.  All rights reserved.  
;
; *** End of NetLogo Model Copyright Notice ***
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@#$#@#$#@
WHAT IS IT?
-----------
This model demonstrates finding the Hamming distance of a set of bit patterns.

HOW IT WORKS
------------
Four random bit patterns are generated. Each possible pair of bit patterns is compared; the number of differences between them is the Hamming distance of that pair.  The smallest distance found out of all of the pairs compared is the Hamming distance. 


HOW TO USE IT
-------------
The setup button generates four random bit patterns, of a length specified by the number-of-digits slider.

The slow-motion slider is an easy way to adjust the speed of the display so you can watch the digits change as the red arrow passes.  Set it to zero if you want to just see the answer quickly.  0.3 is a good setting for most purposes.

The number-of-digits slider lets you choose how many numbers are in each bit pattern.

The step button does whatever step comes next, and then stops so you can take notes.

The go button finishes the entire problem, at a speed set by the slow-motion slider.

The show-again button starts the exact problem from the beginning.  You may then click either the step button or the go button to see the same demonstration.

The quiz button generates a random problem and then asks you to determine the answer.  


THINGS TO NOTICE
----------------
The smallest distance should never be zero. If it is zero, then an error has occured (2 of the bit patterns are the same). 

Bit pattern 0 is compared to the other 3 bit patterns, then bit pattern 1 is compared to 2 bit patterns, and finally bit pattern 2 is compared to bit pattern 3.  It doesn't matter which order we compare, so we do not have to compare bit pattern 3 to 0, etc.


THINGS TO TRY
-------------
Set the slow-motion slider to about .30 seconds (or slower) and press the step button a few times.  Watch the demonstration of each step.

Set the slow-motion slider to about .3 seconds and press the go button. What the entire
demonstration.

Do each step by hand, then press step to check your work.


EXTENDING THE MODEL
-------------------
Allow the user to input the beginning four bit patterns.

Allow the user to choose the number of bit patterns to be compared.

Allow the user to choose the order that the bit patterns are compared. 


NETLOGO FEATURES
----------------
"word" is used to put two inputs together and make them a string.

"any? other-turtles-here" is used to find if there are any turtles in a certain place.


RELATED MODELS
--------------
Hamming Code Simulation, Hamming Error Detection


CREDITS AND REFERENCES
----------------------
This model was written by Crystal Barchet and Teresa Carrigan, 2004.  

Permission to use, modify or redistribute this model is hereby granted,
provided that both of the following requirements are followed:
	a) this copyright notice is included.
	b) this model will not be redistributed for profit without permission
	   from Teresa Carrigan.
Contact Teresa Carrigan for appropriate licenses for redistribution 
for profit.

To refer to this model in academic publications, please use: 
Barchet, C. and Carrigan, T. (2004). Hamming Distance Simulation 
Blackburn College, Carlinville, IL.

In other publications, please use: 
Copyright 2004 by Crystal R. Barchet and Teresa Carrigan.  All rights reserved.  


FOR MORE INFORMATION 
-------------------- 
For more information about Hamming Distance, see one of the following textbooks:
[1] Null, L. and Lobur, J. "Essentials of Computer Organization and Architecture", First Edition, Jones & Bartlett,  pages 77-78.
[2] Murdocca, M. and Heuring, V. "Principles of Computer Architecture", First Edition, Prentice Hall, page 360
@#$#@#$#@
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NetLogo 2.0.1
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