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what's a persistent variable????

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mohammad asasi
mohammad asasi 2012-5-7
Hi
really I'm confused by persistent variables!!!
please help me to know what are they and their applications???
  1 个评论
Walter Roberson
Walter Roberson 2012-5-7
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采纳的回答

Walter Roberson
Walter Roberson 2012-5-7
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.

更多回答（1 个）

Jan
Jan 2012-5-7
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?

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