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Constants and Aliases

The namespace gcxmlib contains following several constants and aliases. This section describes the definitions and general usages.

The following constants are used to convert angles in different scales.

constexpr double radian_to_degree = 180./M_PI;
constexpr double degree_to_radian = M_PI/180.;
constexpr double radian_to_arcmin = 60.*180./M_PI;
constexpr double arcmin_to_radian = M_PI/180./60.;
constexpr double radian_to_arcsec = 3600.*180./M_PI;
constexpr double arcsec_to_radian = M_PI/180./3600.;

By using namespace gcxmlib::literals, you can use the following user-defined literals to define angles.

namespace literals {
  /** user-defined literal for radian. */
  const angle operator"" rad(long double ang)
  { return radian(ang); }
  /** user-defined literal for degree. */
  const angle operator"" deg(long double ang)
  { return degree(ang); }
  /** user-defined literal for arcminute. */
  const angle operator"" amin(long double ang)
  { return arcmin(ang); }
  /** user-defined literal for arcsecond. */
  const angle operator"" asec(long double ang)
  { return arcsec(ang); }
}

An example is provided below. An angle instance is defined in a user-friendly style using literals, instead of degree(1.0).

using namespace gcxmlib::literals;
const angle one_degree = 1.0deg;

The gcxmlib depends on std::chrono. Aliases of frequently used names are provided as follows. Note that the duration of default_clock is different from sec_t. Thus, calculations between timestamp_t and sec_t is not defined. To advance/roll back the timestamp instance, use advance_timestamp().

using sec_t = std::chrono::duration<double>;
using default_clock = std::chrono::system_clock;
using timestamp_t = std::chrono::time_point<default_clock>;

Miscellaneous constants

The constants below are defined for the internal use. If __debug__ is set true, messages for debugging are enabled.

constexpr bool __debug__ = false;
constexpr double __epsilon__ = 1e-12;
constexpr double __exact_zero__ = 0.0;