while loop within while loop within an else

Question

I have a while loop within an else statement. while the condition in the while loop is true I have the variable k decreasing (k=k-1). I want for the while loop to stop before k==0. I have tried placing the while loop within another while loop (while k>1) thinking maybe that would cancel the inner loop if k dropped to 1. Any thoughts?

if yada yada
    do thing1
else
    while k>1
        while x==true
            k=k-1;
            do thing2
        end
    end
end

Using an if statement inside should indeed do the trick, even though ... I really don't see the point of your while here ! — Peut22
– Peut22, Commented Aug 13, 2015 at 6:10
I may have oversimplified the code here..I am trying to iterate through a vector (originally this was all in a for loop), if a first condition is satisfied I want to do a thing and continue iterating through, else I want to look at a second condition, while that second condition remains true I want to do a second thing irrespective of the first condition which led me to that else statement...i figured a while statement within an else was the best way to do this? When condition 2 stops being true I want to return to the next iteration of the for loop (i.e. the if/else statement) — user3470496
– user3470496, Commented Aug 13, 2015 at 16:48
@user3470496, please consider accepting an answer if any one of those helped you solve the problem. It's the tick mark on the left side of the answer. (Questions that have answers, but appear unanswered clutters the front page, so accepting an answer is benefits all of us) =) — Stewie Griffin
– Stewie Griffin, Commented Jul 5, 2016 at 8:10

Dan · Accepted Answer · 2015-08-13 08:54:36Z

3

Doesn't this do the trick?

if yada yada
    x = f(x)   %// If you don't have anything here, you should use "if ~yada yada"
               %// instead of "else"
else
    while k>1 && x == true  %// BTW: Lower case t in true 
        x = g(y)  %// I hope you have something more than "k=k-1" in this loop
        k = k-1;
    end
end

edited Aug 13, 2015 at 8:54

Dan

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answered Aug 13, 2015 at 7:22

Stewie Griffin

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2 Comments

Dan Over a year ago

Using && in the loop condition (i.e. while k>1 && x == true) is definitely the way to go, except it should just be while k>1 && x

Dan Over a year ago

only because x is a bad choice of variable name. If is was called isChecked or something relevant then it would be clearer then having the == true (closer to English what you'd say in English at least)

milez · Accepted Answer · 2015-08-13 06:36:35Z

0

You could add this sentence to be the last thing on your innermost while

if k <= 1
   break;

answered Aug 13, 2015 at 6:36

milez

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Comments

EelkeSpaak · Accepted Answer · 2015-08-13 08:57:16Z

0

Since your while-loop is basically achieving a counter-increment, I would highly recommend replacing it (actually, both of them) with a for-loop. In addition to being much more readable, it will allow Matlab to apply optimizations which will result in much faster execution times. See here:

yadayada = false;
x = true;

if yadayada
else
    kmax = 5;          % or whichever maximum value you want k to have
    for k = kmax:-1:2  % have k start at kmax, decrement by 1 each time, until k==2
        fprintf('k = %d\n', k);

        % do something useful in the loop

        if ~x
            break;
        end
    end
end

Output:

k = 5
k = 4
k = 3
k = 2

answered Aug 13, 2015 at 8:57

EelkeSpaak

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