how to use while loop

i have written a code to find the mod and dividend values of an image.if i

use while loop its getting executed continuously with out stop..can any one

help me where i am wrong...Thanks in advance

share = [250 250 ]

k=ceil(log(250)/log(5));

[r,c]=size(share)

for m= 1:r

        for n = 1:c

        while  share(m,n)>=0

            digits=mod(share(m,n),5)

             share(m,n)=ceil(share(m,n)/5)

        end

    end
end

Answer 1

[Walter Roberson]

Suppose share(m,n) was 1. Then 1/5 is 0.2 and ceil(0.2) is 1. Opps, infinite loop!

Answer 2

[Matt Fig]

Think about this for a second: share(m,n) is initially positive. Then you repeatedly divide it by 5 in the inner while loop. How do you expect to ever get share(m,n) to be negative simply by dividing it by 5? But that is exactly what is needed to break that inner while loop....

For all x > 0: x/5 > 0, correct? So of course x/5 >= 0