Convert scientific notation to decimal in C++

Question

I want to be able to output in decimal and not scientific for all cases in my code.

If I have 122041e+08 then I want it to display as 122041000

If I have 4.6342571e+06 then I want it to display as 4634257.1

... and so on.

Using my code, the output for 4.6342571e+06 is 4634257.100000

void conversion(double counts)
{
  std::ostringstream ss;
  ss << std::fixed << counts;
  std::cout << ss.str() << " MeV";
}

Can someone explain to me why it adds 0's to the end and if it's possible to remove them.

Ozmo

Answer 1

There is a method in your output string stream called precision. You can use it to adjust the number of digits after the comma. It defaults to 6 and missing digits are filled up with 0s (hence the name fixed). In order to achieve 4634257.1 being displayed, set precision to 1:

void conversion(double counts)
{
  std::ostringstream ss;
  ss.precision(1);
  ss << std::fixed << counts;
  std::cout << ss.str() << " MeV";
}

Grandmother

Answer 2

You can use std::setprecision.

Lumumba

ideone.com/5CmObK see here scientific number is converting into normal float number by use of std::fixed rather than std::setprecision. I don't claim mine is right but I am telling you what I observing. I am new to c++; – Frequentation

Answer 3

It adds the zeros because you've (unknowingly) asked for them. The default precision is 6, and in fixed format, that means 6 digits after the decimal (regardless of how many before). The precision has a different meaning according to the format being used for the output. (Which doesn't sound very orthogonal, but works out well in practice, once you know what to expect.)

Balk