Repeating decimal numbers

[fpiro07]

Is there a way to know if a given number has got a repeating part?

[vlad from moscow]

What is the repeating part?

[LamiceDaxeh]

fpiro, it would be very helpful if you'd give an example.

12535 has a repeating part-- 5.

3866556 has two repeating parts-- 66 and 55

3579728712972885 has a repeating part-- 972

The result of dividing 481486 by 37 has a repeating part-- the 135 in 13013.135135135135135135135...

Lamice

[fpiro07]

I'm sorry, I didn't explain myself well.

I was talking about the repeating part of floating point numbers, for example "1.22222222222", "0.3333333333" and so on.

If the user inputs one of those numbers, how can I know whether the number is repeating or not?

[Chervil]

I don't know if there is a way. For one thing, the floating point numbers are stored internally using binary, so that decimal 0.1 ends up with a repeating representation internally. Therefore, you are most likely interested only in whether the decimal representation repeats.
For example, 1/7 = 0.142857142857142857...
and 1/17 = 0.058823529411764705882352941176470...
But in the general case, you are likely to run out of precision before you are able to check this properly.

[Moschops]

If the user inputs one of those numbers, how can I know whether the number is repeating or not?

That's impossible. You're asking me, the user to input a number. I input this number:

0.3333333

Can YOU tell me now if I mean one third (i.e. repeating), or if I actually mean exactly 0.3333333? You cannot. There is no way to know. You cannot program something that's impossible.

[fpiro07]

I think I'm gonna write a class to implement those numbers.

There actually is one of these things in mathLab.

Thank you for your help, anyway.