double_imanip.h

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//   File description
 
#ifndef double_imanip_h
#define double_imanip_h
 
#include <fstream>
#include <limits>
#include <stdexcept>
 
#include "debug.h"
 
#include <fast_float/fast_float.h>
 
class double_imanip {
 public:
  const double_imanip& operator>>(double& x) const {
    std::istream& is = *in;
    std::string buf;
 
    // Read to the buffer
    is >> buf;
    ARTS_USER_ERROR_IF(is.fail(), "Cannot read from stream")
 
    // Actual conversion
    const auto res =
        fast_float::from_chars(buf.c_str(), buf.c_str() + buf.size(), x);
 
    // Error (only std::errc::invalid_argument possible)
    ARTS_USER_ERROR_IF(res.ec == std::errc::invalid_argument,
                       "The argument: \n\n'",
                       buf,
                       R"--('
 
is not convertible to a valid double.  At the very least it
cannot be converted to one using the standard string-to-double
routine
)--")
 
    // Put the stream to be where it is supposed to be
    std::size_t n = std::distance(buf.c_str(), res.ptr);
    while (n++ < buf.size()) is.unget();
 
    return *this;
  }
 
  std::istream& operator>>(const double_imanip&) const { return *in; }
 
  friend const double_imanip& operator>>(std::istream& in,
                                         const double_imanip& dm);
 
 private:
  mutable std::istream* in;
};
 
inline const double_imanip& operator>>(std::istream& in,
                                       const double_imanip& dm) {
  dm.in = &in;
  return dm;
}
 
#endif