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Relive

For-Next loop: stop value as Random()

7 posts in this topic

#1 ·  Posted (edited)

Excuse me if I have not learned of the mechanics of a for-loop well to this day... But this is bugging me.

Code:

For $b = 1 to Random(3, 20, 1)
...
Next

We are now faced with a challenge about for-loops: mechanics of it (in the context of AutoIt) vs. our logic. In the AutoIt Help file for For...To...Step...Next, there states:

If stepVal or stop is a variable, its value is only read the first time the loop executes.

 

Question: We have Random(3, 20, 1) as the stop value, not variable because the function always return a value. But for every iteration, does Random() keep executing its statements or does the placement of the stop value is read once ONLY at the beginning?

Edited by Relive

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It's only executed once in a for loop. Adding ConsoleWrite() to the loop would have been a clue.


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Updated: 04/09/2015

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It's only executed once in a for loop. Adding ConsoleWrite() to the loop would have been a clue.

Do you mean this?:

for $b = 1 to ConsoleWrite(Random(3, 20, 1))
...
Next

It would output a number from 3 to 20 once and the script ends. What happen to actually looping?

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No, this...

For $i = 1 To Random(3, 20, 1)
    ConsoleWrite($i & @CRLF)
Next

This will output a number from 1 to (3 - 20).


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Updated: 04/09/2015

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Think of it this way ... at "next" ... it returns to the line immediately following the "for"


Lofting the cyberwinds on teknoleather wings, I am...The Blue Drache

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#6 ·  Posted (edited)

You would have to do something like this, given your example, and expectations:

$iMax = 20
$iMin = 3
For $i = 0 To $iMax
    If $i > Random($iMin, $iMax, 1) Then
        ConsoleWrite("Exit loop on $i=" & $i & @CRLF)
        ExitLoop
    EndIf
    ConsoleWrite($i & @CRLF)
Next
Edited by jdelaney

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#7 ·  Posted (edited)

Do you mean this?:

for $b = 1 to ConsoleWrite(Random(3, 20, 1))
...
Next

It would output a number from 3 to 20 once and the script ends. What happen to actually looping?

 

:) You put a smile on my face. The return value from ConsoleWrite will be a number: sometimes 1 (digit length) and sometimes 2. The loop will run either once or twice, but the output will only be written once - why? - because the expression in the first line is only evaluated once, as guinness said, when the loop is first initiated. There is actually nothing at all happening inside the loop. If you put something in there, you will notice it sometimes loops twice.

Numeric return value for ConsoleWrite:

The amount of data written. If writing binary, the number of bytes written, if writing text, the number of characters written.

Edited by czardas

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