math_utils.h

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 *       - Pierre-Henri WUILLEMIN(_at_LIP6)                                 *
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#ifndef GUM_MATH_H
#define GUM_MATH_H
 
#include <cmath>
#include <limits>
 
#ifndef M_LOG2E
#  define M_LOG2E 1.4426950408889634074 /* log_2 e */
#endif
 
#ifndef M_PI
#  define M_PI 3.14159265358979323846
#endif
 
#ifndef M_LN2
#  define M_LN2 0.69314718055994530942 /* log_e 2 */
#endif
 
#ifndef GUM_LOG_SQRT_2PI               // std::log ( std::sqrt ( 2pi ) )
#  define GUM_LOG_SQRT_2PI .91893853320467274177
#endif
 
#define GUM_LOG2_OR_0(x) ((x == 0.0) ? 0.0 : std::log2((x)))
 
// redefined due to a strange bug in visual c++
namespace gum {
  template < typename T >
  bool isfinite(T arg) {
    if constexpr (std::numeric_limits< T >::has_infinity) {
      if constexpr (std::numeric_limits< T >::is_signed) {
        return arg == arg && arg != std::numeric_limits< T >::infinity()
            && arg != -std::numeric_limits< T >::infinity();   // neither Nan, infty nor -infty
      } else {
        return arg == arg
            && arg != std::numeric_limits< T >::infinity();    // neither Nan nor inftty
      }
    } else {
      return arg == arg;                                       // not Nan
    }
  }
}   // namespace gum
 
#endif /* GUM_MATH_H */