Problem changing For Loop Maximum inside the loop

[Mackeral]

Consider the following code:

    Last = 10
    For I = 1 To Last
        Last = Last + 1
    Next I

At the end of the code you find I = 11 and Last = 21.

The implication of this is that once you set the Maximum for the loop, you can't change it.

So you have to use a Do While loop explicitly testing for the changed Maximum.

 

[JoeMo]

Not sure what your question is, but at the end of the looping Last = 20, not 21.

Sub test()
Last = 10
    For i = 1 To Last
        Last = Last + 1
    Next i
    MsgBox Last & vbCrLf & i
End Sub

 

[Rick Rothstein]

The implication of this is that once you set the Maximum for the loop, you can't change it.

Correct... the loop limits are set immediately before the loop begins and cannot be changed by anything you do within the loop.

 

[Mackeral]

Yes, this is what I discovered. From my point of view (and something I find that often happens to me when I've been working with a piece of code over a long time), I understand how it should work in a way that I hadn't considered when I first wrote it. But it certainly took a long time to actually figure out what was going on in code that I expected to work since it was in the system programming. There is nothing I have ever encountered before that had this limit hard wired and un-documented feature before.

 

[Mackeral]

One other comment:
Don't forget to explicitly update the control variable which was handled by the "For Loop".

 

[RoryA]

There is nothing I have ever encountered before that had this limit hard wired and un-documented feature before.

It's actually clearly documented in the language spec.