[Gambas-user] A random sort of listview

[Jussi Lahtinen]

Hi!

I can't reproduce your problem.
Randomize with seed 12345, I got;
>From 0 to 9: 4 0 7 9 5 1 2 6 3 8
>From 9 to 0: 4 2 7 8 3 0 6 9 1 5
Both correct.

So maybe there is a bug in SWAP command with Gambas version... what
are you using?
With Gambas 2.10 it is working.


Jussi


P.S. Code I used to test:

DIM ii AS Integer
DIM jj AS Integer
DIM a AS Integer
DIM myArray AS Integer[200]
DIM checkArray AS NEW Integer[]

RANDOMIZE 12345

FOR ii = 0 TO 9 '199
myArray[ii] = ii
NEXT

FOR ii = 0 TO 9 '199 ' random swap array items
a = Int(Rnd(ii + 1))
SWAP myArray[ii], myArray[a]
NEXT


FOR ii = 0 TO 9 '199 ' Check against duplicates.
PRINT myArray[ii]
 FOR jj = 0 TO 9 '199
 IF myArray[ii] = jj THEN
  IF checkArray.Exist(jj) = FALSE THEN
  checkArray.Add(jj)
  ELSE
  Message.Error("Error!")
  RETURN
  ENDIF
 ENDIF
 NEXT
NEXT


PRINT checkArray.Count



On Wed, Apr 8, 2009 at 00:12, Simonart Dominique
<simonart.dominique at ...11...> wrote:
> Hi,
>
> jbskaggs a écrit :
>> Okay,
>>
>> But why does it do that?  I don't see why the direction should matter what
>> am I missing ?  Becuase maybe this is something that has plagued me and
>> caused me headaches for a while.
>>
>> JB Skaggs
>>
>
> You're right! Thanks!
> My mistake is that I listed the myArray values inside the
> SAME for next loop that the swap! But of course, the values
> could change at each next step
>
> However, there is differences. Let see a step by step sample
>
> CASE 1: Forward FOR NEXT loop
>
> * i=0 -> Int(Rnd(i+1)) = 0!
> you could affect only myArray[0] to myArray[0]
> * i=1 -> Int(Rnd(i+1)) = 0-1
> you could affect myArray[0] once more
> * i=2 -> Inn(Rnd(i+1)) = 0-2
> idem
> * i=3 ...
> at each step, ALWAYS you could affect an already selected value
>
> CASE 2: Backward FOR NEXT loop
>
> * i=199 -> Int(Rnd(i+1)) = 0-199
> myArray[199] could be any value
> * i=198 -> Int(Rnd(i+1)) = 0-198
> myArray[198] could be any of the non selected values
> myArray[199] will never be affected anymore
> * i=197 ...
> at each step, NEVER you could affect an already selected value
>
> I found the second case more satisfying for my mind! :)
>
> Hope this send your headache away! :)
> Dominique Simonart
>>
>>
>>
>> Simonart Dominique wrote:
>>> Hi,
>>>
>>> jbskaggs a écrit :
>>>> When I ran the code it ran fine- why is it important to have it  count
>>>> backwards in the random swap?
>>>>
>>>> ie for i =199 to 0 step -1 instead of for i=0 to 199 step 1?
>>>>
>>>> JB SKaggs
>>>>
>>> Strange, because it should not  :)
>>> run a test with 10 numbers 0-9 and fixe the seed with
>>> RANDOMIZE 12345
>>> If you run the forward FOR NEXT you will get:
>>> 0 0 2 3 1 1 2 6 3 8
>>> which is wrong!
>>> but if you run the backward FOR NEXT you will get:
>>> 5 1 9 6 0 3 8 7 2 4
>>> which is right!
>>>
>>> May be you did not notice it because 200 is long enough
>>> before you get the same number twice, and before you remark
>>> that some are missing?
>>>
>>> Dominique Simonart
>>>
>>>> Simonart Dominique wrote:
>>>>> Hi,
>>>>>
>>>>> Hmm, did you run exactly this code? If so, there is
>>>>> something wrong with the second FOR NEXT loop
>>>>>
>>>>> jbskaggs a écrit :
>>>>>> using your suggestions and the swap command vs manual swapping this is
>>>>>> my
>>>>>> code:
>>>>>>
>>>>>> public b as string  'optional string used to hold the array data for
>>>>>> file
>>>>>> or
>>>>>> split later
>>>>>>
>>>>>> PUBLIC SUB button4_click() ' initialize array
>>>>>> DIM myArray AS Integer[200]
>>>>>> DIM a AS Integer
>>>>>> DIM i AS Integer
>>>>>>
>>>>>> FOR i = 0 TO 199 STEP 1 'add array items
>>>>>>  myArray[i] = i
>>>>>> NEXT
>>>>>>
>>>>>> FOR i = 0 TO 199 STEP 1 ' random swap array items
>>>>>> a = Int(Rnd(i + 1))
>>>>>> SWAP myArray[i], myArray[a]
>>>>>> NEXT
>>>>>>
>>>>> the right code is:
>>>>>
>>>>> FOR i = 199 TO 0 STEP -1
>>>>>     ...
>>>>> NEXT
>>>>>
>>>>>> FOR i = 0 TO 199 STEP 1 ' write items in listview2
>>>>>> listview1.MoveTo(myArray[i])
>>>>>> c = listview1.Item.Key
>>>>>> listview2.add(c, listview1.item.text)
>>>>>> NEXT
>>>>>>
>>>>>>
>>>>>>
>>>>>> FOR i = 0 TO 199 STEP 1 'optional step to write array as a string for
>>>>>> file
>>>>>> or whatever use
>>>>>> b &= "slot" & myArray[i] & ","
>>>>>> NEXT
>>>>>> PRINT b
>>>>>> END
>>>>>>
>>>>>> PUBLIC SUB Button1_Click() 'an optional way to load the array values
>>>>>> from
>>>>>> the variable b and / or a file if b was file loaded
>>>>>> DIM egg AS String[]
>>>>>> DIM c AS String
>>>>>>  listview1.Clear
>>>>>>  egg = Split(b, ",")
>>>>>>  FOR EACH c IN egg
>>>>>> TRY listview1.Add(c, c)
>>>>>> IF ERROR THEN RETURN
>>>>>> NEXT
>>>>>> IF listview1.Count >= 200 THEN RETURN
>>>>>> END
>>>>>>
>>>>>> JB Skaggs
>>>>>>
>>>>> Dominique Simonart
>>>>>
>>> Dominique Simonart
>>>
>>>
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>
>
>
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