running two while loops

Question

xRobot 2019-11-24

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/492931-running-two-while-loops

回答： Walter Roberson 2019-11-25

采纳的回答： Walter Roberson

在 MATLAB Online 中打开

Hello,

I am attempting to run two while loops similar to below with check being a value zero or 1:

input(enter guess)
check = check(guess)
while check == 0 
do things
input(enter guess)
check = check(guess)
while check == 1 
do things
input(enter guess)
check = check(guess)

The problem I am having is that once I am is that once I enter the second loop and check becomes 0 I cannot go back to the above loop I am stuck in the one where check == 1.

Is this an example of a case where parallel while loop tools would be needed like the parallel toolbox.

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Rik 2019-11-24

Since you rely on user input, it doesn't look to me like this is a parallel process. It looks like you need either two while loops with their own check, or a single loop with two checks in its condition.

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Answer 1

Walter Roberson 2019-11-25

2
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https://ww2.mathworks.cn/matlabcentral/answers/492931-running-two-while-loops#answer_403131

在 MATLAB Online 中打开

As a general form you can use something like

need_to_repeat_outer_loop = true;
while need_to_repeat_outer_loop
    %some code
    need_to_repeat_inner_loop = true;
    while need_to_repeat_inner_loop
        %some code
        if some inner condition
            need_to_repeat_inner_loop = false;
        end
    end
    %some code
    if some outer condition
        need_to_repeat_outer_loop = false;
    end
end

Hower, in practice most of the time you would instead write

while true
    %some code
    while true
        %some code
        if some inner condition
            break;   %out of inner loop
        end
    end
    %some code
    if some outer condition
        break;
    end
end

Sometimes you are inside the inner loop and need to signal that the outer loop is to be stopped. For that you can use

while true
    %some code
    while true
        stop_outer = false;
        %some code
        if some inner condition
            stop_outer = true;
            break;   %out of inner loop
        end
    end
    if stop_outer;
        break;
    end
    %some code
end