/Users/ljp/code/gamma/trunk/Gamma/Constants.h

#ifndef GAMMA_CONSTANTS_H_INC
#define GAMMA_CONSTANTS_H_INC

/*  Gamma - Generic processing library
    See COPYRIGHT file for authors and license information

    File Description: 
    Definitions of numerical constants.
*/


#include "Gamma/pstdint.h"

namespace gam{

#define CONST(N, vf, vd)\
    template <class T> struct N;\
    template<> struct N< float>{ operator uint32_t() const { return vf##UL; } };\
    template<> struct N<double>{ operator uint64_t() const { return vd##ULL; } };

    /*      sign +  expo +  frac =  total
    float   1        8      23      32
    double  1       11      52      64
    */

    CONST(MaskExpo, 0x7F800000, 0x7FF0000000000000) // IEEE-754 floating-point exponent bit mask
    CONST(MaskFrac, 0x007FFFFF, 0x000FFFFFFFFFFFFF) // IEEE-754 floating-point fraction bit mask
    CONST(MaskSign, 0x80000000, 0x8000000000000000) // IEEE-754 floating-point sign bit mask
    CONST(Expo1_2 , 0x3F000000, 0x3FE0000000000000) // IEEE-754 floating-point [0.5, 1) exponent interval
    CONST(Expo1   , 0x3F800000, 0x3FF0000000000000) // IEEE-754 floating-point [ 1, 2) exponent interval
    CONST(Expo2   , 0x40000000, 0x4000000000000000) // IEEE-754 floating-point [ 2, 4) exponent interval
    CONST(Expo4   , 0x40800000, 0x4010000000000000) // IEEE-754 floating-point [ 4, 8) exponent interval
    CONST(ExpoNeg1, 0xBF800000, 0xBFF0000000000000) // IEEE-754 floating-point [-1,-2) exponent interval
#undef CONST

const float justUnder1f = 0.99999997f; //0x3f7fffff;


#if defined(__ppc__)
    const int endian = 1;
#else
    const int endian = 0;
#endif

inline bool isLittleEndian(){ return endian==0; }

namespace{
    const double roundMagic = 6755399441055744.; // 2^52 * 1.5
    
    template<class T> const T roundEps();
    template<> inline const float  roundEps<float >(){ return 0.499999925f; }
    template<> inline const double roundEps<double>(){ return 0.499999985; }
}


// constant macros

// const double pi = 4*atan(1.0);

// math.h sometimes does not include these ANSI C macros.
#ifndef M_E
#define M_E         2.71828182845904523536028747135266250
#endif
#ifndef M_LOG2E
#define M_LOG2E     1.44269504088896340735992468100189214
#endif
#ifndef M_LOG10E
#define M_LOG10E    0.434294481903251827651128918916605082
#endif
#ifndef M_LN2
#define M_LN2       0.693147180559945309417232121458176568
#endif
#ifndef M_LN10
#define M_LN10      2.30258509299404568401799145468436421
#endif
#ifndef M_PI
#define M_PI        3.14159265358979323846264338327950288
#endif
#ifndef M_PI_2
#define M_PI_2      1.57079632679489661923132169163975144
#endif
#ifndef M_PI_4
#define M_PI_4      0.785398163397448309615660845819875721
#endif
#ifndef M_1_PI
#define M_1_PI      0.318309886183790671537767526745028724
#endif
#ifndef M_2_PI
#define M_2_PI      0.636619772367581343075535053490057448
#endif
#ifndef M_2_SQRTPI
#define M_2_SQRTPI  1.12837916709551257389615890312154517
#endif
#ifndef M_SQRT2
#define M_SQRT2     1.41421356237309504880168872420969808
#endif
#ifndef M_SQRT1_2
#define M_SQRT1_2   0.707106781186547524400844362104849039
#endif

// Some other useful constants
#ifndef M_2PI
#define M_2PI       6.283185307179586231941716828464095101      // 2pi
#endif
#ifndef M_4PI
#define M_4PI       12.566370614359172463937643765552465425     // 4pi
#endif
#ifndef M_1_2PI
#define M_1_2PI     0.159154943091895345554011992339482617      // 1/(2pi)
#endif
#ifndef M_3PI_2
#define M_3PI_2     4.712388980384689673996945202816277742      // 3pi/2
#endif
#ifndef M_3PI_4
#define M_3PI_4     2.356194490192343282632028017564707056      // 3pi/4
#endif
#ifndef M_LN001     
#define M_LN001     -6.90775527898                              // ln(0.001)
#endif

// Function for getting values
// printf("%.36Lf\n", 4.0 * M_PI);

} // gam::

#endif