C++ Avoid Rounding Number

Question

I know we can use setprecision to prevent a number to be rounded but what if I don't want to round all of my numbers in the list with the same decimal places? In other words, I want to keep my numbers the same as calculated and each number has its own decimal places.

For example: if we use setprecision(7) then it will give the output up to 7 decimal places for all numbers in my list. What if I have a list of different numbers with different decimal places such as 8 or 10 decimal places? Do I need to do setprecision for each of them? Is there any way to keep my numbers the same as the output after calculated? Ex:0.1234567, 0.123456789, 0.12345678910

#include<iostream>
#include<vector>
using namespace std;
int main()
{
   vector<double> myVec{0.1234567, 0.123456789, 0.12345678, 0.12345678910};

   for(int i = 0; i < myVec.size(); i++)
   {
       cout << myVec[i] << " ";
   }
   return 0;
}

Answer 1

Is there any way to keep my numbers the same as the output after calculated?

Not with floating point types such as double .

These are binary floating points, not decimal. Many exact finite decimal fractions will convert to infinite binary fraction, and rounding would happen. So after you do dobule d = 0.1234567 , the variable d will not contain exactly 0.1234567 , it is rather something close to 0.1234567 representable as double.

A way to deal with this is to have custom data types that are decimal fractions, with fixed or floating point, so that 0.1234567 could be represented exactly.