Is it possible to change the upper end for the runtime variable of for loop during it's runtime?

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Daniel
Daniel 2014-1-14
编辑： dpb 2014-1-14
The problem I have, is that I have a for-loop that iterates up to a certain number, but that number can increase during the runtime of the for-loop. As an example:
max = 10;
for i = 1:2:max
max = max + 1;
end
Is the value of i 10? Or is it more, i.e. does i run until it has caught up to max?
Thank you!

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dpb
dpb 2014-1-14
编辑：dpb 2014-1-14
No, the limit is stored and not updated even if the limit variable is modified...this is easily enough tested (and it's in the doc's somewhere altho not in the text help for for).
>> N=4;for i=1:N, disp(i), if i==3, N=N+1; end,end
1
2
3
4
>> disp(N)
5
>>
Use a while loop or similar construct instead of for to have a dynamic upper limit ( break may be your friend here, too).

更多回答（1 个）

Dana Adkins
Dana Adkins 2014-1-14
In short, “No.”
By just quickly running your example script the workspace variables end up being i=9 and max = 15 which would imply that while you can modify max however a copy of max’s value is used for the loop limit and not your newly modified max value.
This is not a practice I would recommend in any case.

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