There something wrong about mod function

This is my script function code:

function test(n)
  n2=mod(n,1)
  while (n2) ~= 0
      n2 = mod((n2)*10,1);
  end
n2;

I try to do this:(example) I put 0.101 into and need the output like n2 = 0.101; n2 = 0.01; n2= 0.1; n2 =0; but there something wrong, because the output of the above code like this:

n2 =

   0.101000000000000

n2 =

   0.010000000000000

n2 =

   0.100000000000000

n2 =

     8.881784197001252e-16

n2 =

     8.881784197001252e-15

n2 =

     8.881784197001252e-14

n2 =

     8.881784197001252e-13

and so on to

n2 =

   0.250000000000000

n2 =

   0.500000000000000

n2 =

     0

So, I don't know why it like this.

Answer 1

[Birdman]

This situation happens due to the fact that

mod(1,1)

is not actually zero, it is really close to zero. You need to indicate a condition whether the value is under a certain tolerance or not. Change your code to the following:

function test(n)
  n2=mod(n,1)
  while (n2) ~= 0
      if ismembertol(n2,fix(n),1e-5) || n2<1e-5
         break;
      else
         n2 = mod((n2)*10,1);
      end 
  end
n2;

With the above if condition, we assume the number n2 as zero if it is smaller than 1e-5.

For further information, please refer to the following link:

https://www.mathworks.com/matlabcentral/answers/57444-faq-why-is-0-3-0-2-0-1-not-equal-to-zero

[Thomas Tin]

But when put 1.101 it till be false

n2 =

   0.101000000000000

n2 =

   0.010000000000000

n2 =

   0.099999999999998

n2 =

   0.999999999999979

n2 =

   0.999999999999787

n2 =

   0.999999999997868

...

[Birdman]

I edited my answer.

[Stephen23]

"This situation happens due to the fact that mod(1,1) is not actually zero, it is really close to zero"

Really?

>> mod(1,1)==0
ans = 1

[Birdman]

Actually the derived 1 from calculation. I forgot to mention that.

[Stephen23]

@Birdman: a 1 derived from a calculation would still be a 1. Your wording could be improved to correctly point out that the value obtained by this calculation is not equal to 1. Currently your answer implies that 1 is not equal to 1, which is incorrect and misleading.

[Birdman]

Yes, exactly. Sorry for misinformation. I meant the value obtained by this calculation is not equal to 1.