Better way to handle numbers in my case

I have the need to use big numbers in C++. C++ hasn't native support for big numbers. I have to represent big numbers, do multiplication,addition,exponentiation and division. Furthermore the result of the division is a decimal number but surely is in the range [0 1], thus I have not to represent big decimal number, but big integer number alone but I want pick the decimal results (in a double of C++) of a division between big integers.
Given my needs is it convenient to implement code from myself? I do not think so, because there is the need of a lot of operations. So the solution to my needs would be to use an external library?Which library could I use? I have a look at this library:http://ift.tt/2vjsFF6 but may be that in my case i should use a library a library for handle double because I have to pick the "double" result of a big integer division. Furthermore this library offers additional functionality that I do not need .

(I'm using C++11 compiler and I'm in Ubuntu 64 bit)