_FLT_MAX _FLT_MIN _M_1_PI _M_1_SQRPI _M_2_PI _M_2_SQRTPI _M_2PI _M_D2R _M_E _M_LN10 _M_LN2 _M_LOG10E _M_LOG2E _M_PI _M_PI_2 _M_PI_3 _M_PI_4 _M_PI_6 _M_R2D _M_SQRT1_2 _M_SQRT2 _MGZERO _SIZE_T isnan mgCopy mgEquals mgHypot mgIsZero mgMax mgMin mgRound mgSquare mgSwap size_t

_MGZERO const float _MGZERO = 2e-6f 定义可以视为零的极小数