test-chrono.cpp

#include <boost/format.hpp>
#include <boost/lexical_cast.hpp>
#include <iostream>
#include <chrono>

main(){

  namespace c = std::chrono;

  typedef c::duration<double> real64_seconds;
  typedef c::duration<float> real32_seconds;

  auto pi = "3.1415926535897932384626433832795028841971";
  auto a = real64_seconds(boost::lexical_cast<double>(pi));
  auto b = c::duration_cast<real32_seconds>(a);

  std::cout
    << pi << "\n"
    << boost::format("%.32f") % a.count() << "\n"
    << c::duration_cast<c::milliseconds>(a).count() << "\n"
    << c::duration_cast<c::microseconds>(a).count() << "\n"
    << c::duration_cast<c::nanoseconds>(a).count() << "\n"
    << c::duration_cast<real32_seconds>(a).count() << "\n"
    << boost::format("%.32f") % b.count() << "\n"
    << c::duration_cast<c::nanoseconds>(b).count() << "\n"
    ;

}

(result)

3.1415926535897932384626433832795028841971
3.14159265358979311599796346854419
3141
3141592
3141592653
3.14159
3.14159274101257324218750000000000
3141592832