Problem with my function

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Febin Benjamin
Febin Benjamin 2014-7-9
评论： per isakson 2014-7-9
I have a fitness function as shown below.
function z=sample_fit(r)
Flag=0;
while ~Flag
//take inputs from user
Flag=1;
end
//process the inputs
The above function is called for n times by a GA solver. The problem is that, use of flag in the function is useless as it is always set to zero on every iteration. I want the user to be requested for input only once in the first iteration and for rest of the iterations it will use the values provided in the first iteration.

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回答（1 个）

per isakson
per isakson 2014-7-9
If in the first iteration the word, iteration, means call of the function, sample_fit, see persistent, Define persistent variable
  2 个评论
Febin Benjamin
Febin Benjamin 2014-7-9
Per isakson, you mean like this?
function z=sample_fit(r)
persistent Flag;
Flag=0;
while ~Flag
//accept inputs from user
Flag=1;
end
//process inputs
per isakson
per isakson 2014-7-9
If you make a simple example to try this construct you will find that it doesn't work. Flag=0 (btw: I prefer Flag=false) will be executed every time; nothing achieved with persitent.
See first example in documentation of persistent. You need something like
if isempty( Flag )
Flag = false;
end

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