What is wrong with the code?

Question

aditya 2011-5-4

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/6779-what-is-wrong-with-the-code

I have this small code:

function test
  L = 10;
  t = existing_chk('L',uigetdir)
function x = existing_chk(name_x,a)
      chk = exist(name_x,'var')
      if chk == 0;
          x = a;
      else
          x = eval(name_x);
      end
end
end

The problem is that uigetdir is executed even though 'L' exists. I cannot figure out the problem

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Answer 1

Kelly Kearney 2011-5-4

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在 MATLAB Online 中打开

The uigetdir function is being called on line 2 of your function, prior to existing_chk ever being called, since you have not enclosed the function name in quotes. The second argument of existing_chk should be a string. Replace that line with

t = existing_chk('L','uigetdir')

You should probably avoid using eval too, but that's just general programming advice; the function should work as written.

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aditya 2011-5-4

Thanks Kelly.

Another thing - is there an alternative in this case to eval ?

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Answer 2

Daniel Shub 2011-5-4

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MATLAB evaluates uigetdir before existing_chk, so that it can pass whatever uigetdir returns to existing_chk. Either turn the second argument into a function handle @()uigetdir and call a() or turn it into a string 'uigetdir' and call eval(a).