Are statements in a Switch-expression necessary?

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Sam 2014-12-20

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https://ww2.mathworks.cn/matlabcentral/answers/167339-are-statements-in-a-switch-expression-necessary

评论： matt dash 2014-12-20

This is my code:

for welke_pp=1:aantal_pp
  switch welke_pp
      case 1
      case 2
      case 3
      case 4
      case 5
    end
...

I started a for-loop for 5 subjects. Then I switch them by case 1,2,3,4 and 5. Because the whole for-loop is completely the same for each subject (except for the selected data), I wonder if 'statements' under each 'case-expression' are really necessary for my program?

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dpb 2014-12-20

No, but in that case there's no need for the specific case either

matt dash 2014-12-20

在 MATLAB Online 中打开

You seem to be misunderstanding the purpose of a switch statement. If the cases are empty, the entire statement does absolutely nothing. The empty switch statement you have is equivalent to:

if welke_pp==1
elseif welke_pp==2
elseif welke_pp==3
elseif welke_pp==4
elseif welke_pp==5
end

You seem to be implying that you think that the switch statment itself is actually changing welke_pp. It doesn't... that is handled by the for loop. The switch statement only looks at the value of welke_pp and performs an action depending on what value it sees (the cases).

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回答（1 个）

Guillaume 2014-12-20

1
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在 MATLAB Online 中打开

You can have a case without any statement, but there is no point writing that specific case in the first place, unless you also have an otherwise. The otherwise catches all the values that have not been dealt with a particular case. You can also regroup case values together if the statements are the same:

switch welke_pp
   case 1       %handle value 1
     do_fun;
   case {2, 3}  %handle value 2 and 3
     do_otherfun;
   case 4       %handle value 4
     %does nothing
   otherwise    %handle all other values
     do_somethingelse;
end