Repeat Try/Catch loop?

I have code that sometimes results in an error, and sometimes not. I'd like to have the code run, and then if an error occurs try again until there is no error. Could this be done using a try/catch loop? I.e. the catch statement would tell the program to repeat the try statements? I'm not sure how to implement this.

Thanks!

Answer 1

[Evan]

You could embed your try/catch statements in a while loop, then check a condition at the beginning each iteration to see if the previous iteration ended in an error.

This could either be done through dealing with the MException object itself or just through setting a counter both inside the catch portion and outside the try/catch statement. When the two counters don't match up, you know that you have just had a successful run.

count = 0;
err_count = 0;
while count == err_count
    try
        i = randi(9);
        if i ~= 7
            error
        end
    catch MyErr
        err_count = err_count + 1;
    end
    count = count + 1;
end

[Achmad Rizal]

any alternative form with "for" loop?

[DGM]

Here's an idea, though I don't really know why a while loop couldn't be used.

maxtries = 20;
failcount = 0;

for k = 1:maxtries
    try
        sometimeserror(0.8);
        break;
    catch
        failcount = failcount + 1;
    end
end


function sometimeserror(p)
    % p is the probability of error
    if rand() < p
        error('oh gosh i''m so sorry.  my bad.');
    end
end

[Voss]

@Achmad Rizal:

count = 0;
err_count = 0;
max_n_tries = 10; % max number of tries
success = false;
for jj = 1:max_n_tries
    try
        i = randi(9);
        if i ~= 7
            error
        end
    catch MyErr
        err_count = err_count + 1;
    end
    count = count + 1;
    if count ~= err_count
        % stop looping as soon as count ~= err_count
        success = true;
        break
    end
end

Or, an alternate while loop:

while true
    try
        % something that might throw an error
        break
    end
end

Answer 2

[Daniel Shub]

You could do something like

function varargout = myfunc(varargin)
  try
     thingThatSometimesCrashes;
  catch
    [vargout{1:nargout}] = myfunc(varargin{:})
  end
end

This is a recursive loop. If thingThatSometimesCrashes crashes too many times in a row, the function will exceed the recursion limit and still crash. You could instead do a loop with a flag

function varargout = myfunc(varargin)
  myflag = true;
  while myflag
    try
       thingThatSometimesCrashes;
       myflag = false;
    end
 end
end