Question

I want to store a float value into string without lossing or adding any single precision digits.

For example if my float value is 23.345466467 , I want my string to have str = “23.345466467” exact digits.

I tried using CString format function with %f. Its giving only first 6 precision.
or if i use %10 , if my float value is having less than 10 precision,its adding some more junk precision. I want to get exact float value into my string. how to do this?

Answer 1

1st of all: you can’t convert floating to string and back without probably loosing a bit or two. As it is not 1-to-1 conversion as they use different base.

For preserving the best accuracy for floating point type:

std::string convert(float value)
{
  std::stringstream ss;
  ss << std::setprecision(std::numeric_limits<float>::digits10+1);
  ss << value;
  return ss.str();
}

Or more generic

template<typename FloatingPointType>
std::string convert(FloatingPointType value)
{
  std::stringstream ss;
  ss << std::setprecision(std::numeric_limits<FloatingPointType>::digits10+1);
  ss << value;
  return ss.str();
}

It would cut off digits you do not need but keep highest precision possible.