Visual Basic, Advanced Programming Question

Tim Bernema
#1 / 7

Advanced Programming Question

If I have a While loop inside a For loop and do a Exit For in the While loop
am I not cleaning up right? I'm worried (knowing VB and Microsoft) that
pointers are not being popped off the stack correctly or something like
that. Another external event sets x and y. Example:

Private Sub SomeProcedure()
tmrPoll.Interval = 5000
For i=1 To 3
tmrPoll.Enabled = True
While tmrPoll.Enabled
DoEvents
If x=y Then Exit For '<--Is this gonna cause a problem?
Wend
If x=y Then Exit For
Next
End Sub

Private Sub tmrPoll_Timer()
tmrPoll.Enabled = False
End Sub

Tim :)

Tim Berneman

President of Central Iowa Visual Basic User Group (CIVBUG)
Webmaster of Central Iowa Visual Basic User Group (www.civbug.org)

Wed, 06 Mar 2002 03:00:00 GMT

doco
#2 / 7

Advanced Programming Question

Looks pretty sanitary to me.

doco

Quote:

> If I have a While loop inside a For loop and do a Exit For in the While
loop
> am I not cleaning up right? I'm worried (knowing VB and Microsoft) that
> pointers are not being popped off the stack correctly or something like
> that. Another external event sets x and y. Example:

> Private Sub SomeProcedure()
> tmrPoll.Interval = 5000
> For i=1 To 3
> tmrPoll.Enabled = True
> While tmrPoll.Enabled
> DoEvents
> If x=y Then Exit For '<--Is this gonna cause a problem?
> Wend
> If x=y Then Exit For
> Next
> End Sub

> Private Sub tmrPoll_Timer()
> tmrPoll.Enabled = False
> End Sub

> Tim :)

> Tim Berneman

> President of Central Iowa Visual Basic User Group (CIVBUG)
> Webmaster of Central Iowa Visual Basic User Group (www.civbug.org)

Wed, 06 Mar 2002 03:00:00 GMT

ay..
#3 / 7

Advanced Programming Question

Quote:

> If I have a While loop inside a For loop and do a Exit For in
> the While loop am I not cleaning up right? I'm worried (knowing VB
> and Microsoft) that pointers are not being popped off the stack
> correctly or something like that.

No. This is not recursion. No pointers are involved.

Quote:

> Tim Berneman

> President of Central Iowa Visual Basic User Group (CIVBUG)
> Webmaster of Central Iowa Visual Basic User Group (www.civbug.org)

-Amos Yung

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Share what you know. Learn what you don't.

Thu, 07 Mar 2002 03:00:00 GMT

RJol
#4 / 7

Advanced Programming Question

Use a Do loop so you can exit it instead:

Private Sub SomeProcedure()
tmrPoll.Interval = 5000
For i=1 To 3
tmrPoll.Enabled = True
Do While tmrPoll.Enabled
DoEvents
If x=y Then Exit Do
Loop
If x=y Then Exit For
Next
End Sub

Quote:

> If I have a While loop inside a For loop and do a Exit For in the While
loop
> am I not cleaning up right? I'm worried (knowing VB and Microsoft) that
> pointers are not being popped off the stack correctly or something like
> that. Another external event sets x and y. Example:

> Private Sub SomeProcedure()
> tmrPoll.Interval = 5000
> For i=1 To 3
> tmrPoll.Enabled = True
> While tmrPoll.Enabled
> DoEvents
> If x=y Then Exit For '<--Is this gonna cause a problem?
> Wend
> If x=y Then Exit For
> Next
> End Sub

> Private Sub tmrPoll_Timer()
> tmrPoll.Enabled = False
> End Sub

> Tim :)

> Tim Berneman

> President of Central Iowa Visual Basic User Group (CIVBUG)
> Webmaster of Central Iowa Visual Basic User Group (www.civbug.org)

Thu, 07 Mar 2002 03:00:00 GMT

David Winte
#5 / 7

Advanced Programming Question

Looks fine to me. I use Exit Do and Exit For all the time..or at least where
needed.

David

Quote:

>If I have a While loop inside a For loop and do a Exit For in the While
loop
>am I not cleaning up right? I'm worried (knowing VB and Microsoft) that
>pointers are not being popped off the stack correctly or something like
>that. Another external event sets x and y. Example:

>Private Sub SomeProcedure()
> tmrPoll.Interval = 5000
> For i=1 To 3
> tmrPoll.Enabled = True
> While tmrPoll.Enabled
> DoEvents
> If x=y Then Exit For '<--Is this gonna cause a problem?
> Wend
> If x=y Then Exit For
> Next
>End Sub

>Private Sub tmrPoll_Timer()
> tmrPoll.Enabled = False
>End Sub

>Tim :)

>Tim Berneman

>President of Central Iowa Visual Basic User Group (CIVBUG)
>Webmaster of Central Iowa Visual Basic User Group (www.civbug.org)

Fri, 08 Mar 2002 03:00:00 GMT

Mike William
#6 / 7

Advanced Programming Question

Its fine. Try the following, which will run forever:

Private Sub Command1_Click()
Dim a, i
Do
For i = 1 To 3
While a = a
DoEvents
Exit For
Wend
Next i
Loop
Print "done"
End Sub

Mike

Quote:

> Looks fine to me. I use Exit Do and Exit For all the time..or at least
where
> needed.

> David

Quote:

> >If I have a While loop inside a For loop and do a Exit For in the While
> loop
> >am I not cleaning up right? I'm worried (knowing VB and Microsoft) that
> >pointers are not being popped off the stack correctly or something like
> >that. Another external event sets x and y. Example:

> >Private Sub SomeProcedure()
> > tmrPoll.Interval = 5000
> > For i=1 To 3
> > tmrPoll.Enabled = True
> > While tmrPoll.Enabled
> > DoEvents
> > If x=y Then Exit For '<--Is this gonna cause a problem?
> > Wend
> > If x=y Then Exit For
> > Next
> >End Sub

> >Private Sub tmrPoll_Timer()
> > tmrPoll.Enabled = False
> >End Sub

> >Tim :)

> >Tim Berneman

> >President of Central Iowa Visual Basic User Group (CIVBUG)
> >Webmaster of Central Iowa Visual Basic User Group (www.civbug.org)

Sat, 09 Mar 2002 03:00:00 GMT

Bart Late
#7 / 7

Advanced Programming Question

Quote:

>If I have a While loop inside a For loop and do a Exit For in the While loop
>am I not cleaning up right? I'm worried (knowing VB and Microsoft) that
>pointers are not being popped off the stack correctly or something like
>that.

No. It's safe. It used to be, for example in the BASIC on Apple II, that
the FOR counter was on the return stack. I'm not sure about VB, but
Exit For serves exactly to cleanly leave a FOR loop at any time.

But WHILE is nothing but a conditional goto, as is the WEND
(unconditional). Same for DO and LOOP. There's nothing on any stack for
these kinds of loop.

--
Bart.

Sat, 09 Mar 2002 03:00:00 GMT