Calculation accuracies

@noahboerger reported:

- In trevas the result of an operation is kept in double accuracy (e.g. numeric/power_1)
- User tests assume sometimes less accurate results (e.g. user test: 8.006001 trevas: 8.006000999999998)

I think every language will give this kind of result. To be sure of the result, if a particular precision is needed, user can use `round` operator. @hadrienk, can you confirm?