set precision return statement C++

Question

I want to return a double from a function with a set precision! It is that possible ? I want an accuracy of 10^-5 !

For example :

double f(double a ,double b)
{
  //something like return.setprecision(6); 
  return (a+b)/2;
}

Answer 1

Assuming you mean truncated to 5 decimals:

Multiply by 10⁵. Round to integer. Divide result by 10⁵.

For the rounding, use the standard library so that you avoid exceeding the range of an integer type.

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Note that the result can only be perfect for numbers that can be exactly represented. The common representations of floating point numbers are binary, although the C++ standard allows decimal representations. And that means that with most numbers the result will not be exact.