How can I detect if a float has a repeating decimal expansion in C#?

Question

I simply need to know how I can detect repeating decimal expansion in floats.

Example:

0.123456789123456789

The repeating portion of the number would

Answer 1

I don't think that there's solution in general (at least, with float/double):

• period can bee too long for float (or even double);
• float/double are approximate values.

E.g., here's a result of division (double)1/(double)97:

0.010309278350515464

Indeed, it is a repeating decimal with 96 repeating digits in period. How to detect this, if you only have 18 digits after decimal point?

Even in decimal there's not enough digits:

0.0103092783505154639175257732