Use of "Break" in switch statement

I have a switch statement, and I would like to use a "break" to terminate some calculations if the switch statement is fulfilled.

But which statement can I use, which is similar to "break" like used for loops? Cause I have so far just used "exit" but that statement closes Matlab and I only want to abort some calculations but still not close Matlab completely....

Many Thanks!

[Sole gak]

you can use return

%% in case you have a simple switch case 
a = 1; b = 1;
switch a
    case 1
        disp('foo');
        if (b ==1)
            disp('bar');  
            return; 
        end
        disp('bidon');
end

%% this works as well if you have your switch case in a loop 
a = 1; b = 1;
while (true)  
    switch a
        case 1
            disp('foo');
            if (b ==1)
                disp('bar');
                return;
            end
            disp('foobar');
    end
end

Hope that helps,

S'

[Jose]

Commands "break", "continue" and "return" work all very nicely within a "switch / case":

function switch_break
if fn2
    disp('function fn2 went till the end');
else
    disp('function fn2 aborted')
end
% end of switch_break function

function ret= fn2
ret= 0; % return zero if not done all runs
for i= 1:5
    fprintf('i=%d of 5: ', i);
    [~,~, button]= ginput(1);
    switch button
        case 1
            disp('button 1, continue to the next case');
            continue
        case 2
            disp('button 2, break the loop');
            break
        case 3
            disp('button 3, abandon function');
            return
        case 27
            disp('ESC key, continue after the switch')
    end
    disp('  more work done after the switch')
end
disp('  more work done after the loop')
ret= 1; % went till the end

Answer 1

[Walter Roberson]

break will terminate the enclosing loop.

Answer 2

[Anne van Rossum]

The following is a "trick" that will break out of the switch.

for br=1:1
  switch val
    case 'one'
      ...
    if ~some_condition
      ...
      break;
    end
    case 'two'
      ...
    case 'three'
      ...
    otherwise
      ...
  end
end

As you can see, there is an additional for-loop that is run only once with the only purpose to provide a way to break out of the switch statement.

I think the absence of a break in a switch statement is because people thought the only reason for it was to provide fall-through in early C. Personally, I think people should not tell you how to structure your code, so denying someone to break where he/she wants is a bit presumptuous.

Answer 3

[Jiro Doke]

What do you mean by "if the switch statement is fulfilled"? Are you trying to get out of the whole switch-case block while you are inside one of the case statements? I would just use if-else-end in your case statement:

switch val
  case 'one'
    ...
    if ~some_condition
      ...
    end
  case 'two'
    ...
  case 'three'
    ...
  otherwise
    ...
end

If "some_condition" is satisfied, it would get out of the "one" case. Is this what you mean?

Also, in case you're thinking that it works like C, as you can see from the documentation for switch (see Tips), MATLAB switch does not fall through, so you don't need a "break" or "return" after each case statement.

[Nicholai]

I have this line of code:

function closeBar(src,evnt)

|selection = questdlg('Do you want to stop this process?',...

'Stop process',...

'Yes','No','Yes');

switch selection,

case 'Yes',

exit

case 'No'

return

end

It's if case "Yes" is fulfilled I need some statement which stops all the ongoing processes in all the m-files in my work space...

An "exit" function does this but it also closes the entire Matlab application. I only need it to stop the calculations not close the program...

Thank you for your reply!

[Walter Roberson]

Use a call to error()