what's a persistent variable????

Hi

really I'm confused by persistent variables!!!

please help me to know what are they and their applications???

[Walter Roberson]

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Answer 1

[Walter Roberson]

A persistent variable retains its values between calls to the routine.

For example

function trial

    persistent times_called
    if isempty(times_called); times_called = 0; end  %never called before
    times_called = times_called + 1;
    if mod(times_called,10) == 0
      fprintf('Trial called %d times so far\n', times_called);
    end

    %now do the real work of the routine
    .....

end

The above is just one of many uses.

[mohammad asasi]

thanks for your answer

Answer 2

[Jan]

At first I suggest reading the documentation

doc persistent
help persistent

The you can try it:

function myFunc
persistent V
if isempty(V)
  disp('V is empty');
  disp('set V to 1');
  V = 1;
end
V = V + 1;
fprintf('V = %d\n', V);

Save this file and start it through the command line:

myFunc
myFunc
myFunc

And now clear the function and call it again:

clear myFunc
myFunc
myFunc

Clearer now?

[mohammad asasi]

thanks jan for your answer