如何在满足if条件的情况下跳转到for循环中的特定位置？

Question

我有一些图像文件。我正在尝试使用每个文件执行一些计算，如果满足特定条件，我想返回到代码中的特定行并从那里再次运行它。但也只是再一次。不管第二次if条件满足还是不满足，我都想进行下一次迭代。但是，MATLAB 似乎没有 goto 函数，而且使用 goto 意味着糟糕的编程，所以我想我只是为满足 if 条件的特定 'i' 值迭代 for 循环两次。

file = dir('*.jpg');
n = length(file);
for i = 1:n
    *perform some operations on the 'i'th file*
    if 'condition'
        *run the for loop again for the 'i'th file instead of going to the 'i+1'th file*
         i=i-1;
    else
        *go to next iteration*
    end
end

我试图通过将循环内的循环变量 'i' 更改为 'i-1' 来编写代码，这样在下一次迭代中，第 'i' 循环将再次重复但是这样做会给出错误的输出，尽管我不知道我的代码中是否存在其他错误，或者内部循环变量的更改是否是问题的原因。感谢您对此提供任何帮助。

Answer 1

将 for 循环替换为 while 循环以获得更大的灵活性。唯一的区别是您必须手动递增 i，因此这也允许您不递增 i.

根据您的新要求，您可以跟踪尝试次数，并在需要时轻松更改：

file = dir('*.jpg');
n = length(file);

i = 1;
attempts = 1; 

while i <= n
    % perform code on i'th file
    success =  doSomething(); % set success true or false;

    if success
        % increment to go to next file
        i = i + 1;

    elseif ~success && attempts <= 2 % failed, but gave it only one try
        % increment number of attempts, to prevent performing 
        attempts = attempts + 1;
    else % failed, and max attempts reached, increment to go to next file
        i = i + 1;
        % reset number of attempts 
        attempts = 1;
    end
end

Answer 2

考虑到在之后添加的新要求，最简单的方法是在单独的函数中将代码从循环中分离出来：

function main_function

  file = dir('*.jpg');
  n = length(file);
  for i = 1:n
    some_operations(i);
    if 'condition'
      some_operations(i);
    end
  end

  function some_operations(i)
    % Here you can access file(i), since this function has access to the variables defined in main_function
    *perform some operations on the 'i'th file*
  end

end % This one is important, it makes some_operations part of main_function

如何在满足if条件的情况下跳转到for循环中的特定位置？

How to jump to a particular place in the for loop if the if condition is satisfied?

matlab

conditional

for-loop

if-statement

goto