/*! \file lib/clipper_util.h
    Header file for clipper helper functions
*/
//C Copyright (C) 2000-2006 Kevin Cowtan and University of York
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#ifndef CLIPPER_UTIL
#define CLIPPER_UTIL


#include "clipper_precision.h"
#include "clipper_sysdep.h"


namespace clipper
{

  //! Utility class
  /*! This class holds a set of useful static functions and values.
   You should never need to instantiate this class: Refer to members
   using Util:: */
  class Util
  {
  public:
    Util();   //!< null constructor
    //! fast Util::nan() value
    static const ftype& nan() { return nan_; }
    //! fast Util::nan() value
    static const float& nanf() { return nanf_; }
    //! fast Util::nan() value
    static const double& nand() { return nand_; }
    //! set null floating value - a specific value of NaN used for missings
    inline static void set_null( ftype32& f ) { *((uitype32*)&f) = *((const uitype32*)&nanf_); }
    //! set null floating value - a specific value of NaN used for missings
    inline static void set_null( ftype64& f ) { *((uitype64*)&f) = *((const uitype64*)&nand_); }
    //! fast test for null floating value - only works if set from Util::null()
    inline static bool is_null( const ftype32& f ) { return ( *((const uitype32*)&f) == *((const uitype32*)&nanf_) ); }
    //! fast test for null floating value - only works if set from Util::null()
    inline static bool is_null( const ftype64& f ) { return ( *((const uitype64*)&f) == *((const uitype64*)&nand_) ); }
    //! fast Util::nan() test
    /*! Used for missing entries: THIS DOES NOT DISTINGUISH BETWEEN NAN & INF */
    inline static bool is_nan( const ftype32 f ) { return ((*((const uitype32*)&f)&CLIPPER_NAN_MASK_A_32)==CLIPPER_NAN_MASK_A_32); }
    //! fast Util::nan() test
    /*! Used for missing entries: THIS DOES NOT DISTINGUISH BETWEEN NAN & INF */
    inline static bool is_nan( const ftype64 f ) { return ((*((const uitype64*)&f)&CLIPPER_NAN_MASK_A_64)==CLIPPER_NAN_MASK_A_64); }
    //! slow general NaN test for compatibility
    /*! Works for all architectures with IEEE arithmetic only */
    inline static bool isnan(const ftype32 f) { return ((*((const uitype32*)&f)&CLIPPER_NAN_MASK_A_32)==CLIPPER_NAN_MASK_A_32)&&((*((const uitype32*)&f)&CLIPPER_NAN_MASK_B_32)!=0U); }
    //! slow general NaN test for compatibility
    /*! Works for all architectures with IEEE arithmetic only */
    inline static bool isnan(const ftype64 f) { return ((*((const uitype64*)&f)&CLIPPER_NAN_MASK_A_64)==CLIPPER_NAN_MASK_A_64)&&((*((const uitype64*)&f)&CLIPPER_NAN_MASK_B_64)!=0U); }
    //! Sim function: I1(X)/I0(X)
    static ftype sim( const ftype& x );
    //! Inverse Sim function: I1(X)/I0(X)
    static ftype invsim( const ftype& x );
    //! Integral of Sim function: log(I0(X))
    static ftype sim_integ( const ftype& x );
    //! Derivative of Sim function: d/dx( I1(X)/I0(x) )
    static ftype sim_deriv( const ftype& x );
    //! Derivative of Sim function using recurrance: -sim(x)/x + (1 - sim(x)^2)
    static ftype sim_deriv_recur( const ftype& x );
    //! Arc hyperbolic tangent
    static ftype atanh( const ftype& x ) { return log((1.0+x)/(1.0-x))/2.0; }
    //! Modified Bessel function of the first kind
    static ftype bessel_i0( const ftype& x );
    //! Convert isotropic U-value to B-factor
    static ftype u2b( const ftype& x ) { return x * eightpi2_; }
    //! Convert isotropic B-factor to U-value
    static ftype b2u( const ftype& x ) { return x / eightpi2_; }
    //! Convert F+/F- to mean F, with NaN checks
    template<class T> inline static T mean( const T& pl, const T& mi )
      {
	if ( Util::is_nan(pl) ) return mi;
	else if (Util::is_nan(mi) ) return pl;
	else return 0.5*(pl+mi);
      }
    //! Convert sigF+/sigF-/cov to sig F, with NaN checks
    template<class T> inline static T sig_mean( const T& pl, const T& mi, const T& cov )
      {
	if ( Util::is_nan(pl) ) return mi;
	else if (Util::is_nan(mi) ) return pl;
	else if (Util::is_nan(cov) ) return 0.5*sqrt(pl*pl+mi*mi);
	else return 0.5*sqrt(pl*pl+mi*mi+2*cov);
      }

    //! Truncate-to-integer: int(floor(a))
    inline static int intf( const ftype& a ) { return int( floor( a ) ); }
    //! Truncate-to-integer above: int(ceil(a))
    inline static int intc( const ftype& a ) { return int( ceil( a ) ); }
    //! Round-to-integer: int(round(a))
    inline static int intr( const ftype& a ) { return int( rint( a ) ); }

    //! Corrected mod
    inline static ftype mod( const ftype& a, const ftype& b )
      { ftype c = fmod(a, b); if (c < 0) c+=b; return c;}
    //! Corrected mod
    inline static int mod( const int& a, const int& b )
      { int c = a%b; if (c < 0) c+=b; return c; }
    //! max
    template<class T> inline static T max(const T& a, const T& b)
      { return (a > b) ? a : b; }
    //! min
    template<class T> inline static T min(const T& a, const T& b)
      { return (a < b) ? a : b; }
    //! bound a value by limits
    template<class T> inline static T bound( const T& min, const T& val, const T& max ) { return ( (val < max) ? ( (val > min ) ? val : min ) : max ); }
    //! swap the contents of two objects
    template<class T> inline static void swap( T& a, T& b )
      { T c = a; a = b; b = c; }
    //! swap the contents of two objects, using third as store (for speed)
    template<class T> inline static void swap( T& a, T& b, T& c )
      { c = a; a = b; b = c; }
    //! square
    template<class T> inline static T sqr( const T& a ) { return a*a; }
    //! Integer square root (returns floor of sqrt)
    template<class T> inline static T isqrt( const T& n )
      { return T(floor(sqrt(ftype(n)))); }

    //! pi
    inline static const ftype& pi() { return onepi_; }
    //! 2 pi
    inline static const ftype& twopi() { return twopi_; }
    //! 2 pi squared
    inline static const ftype& twopi2() { return twopi2_; }
    //! 8 pi squared
    inline static const ftype& eightpi2() { return eightpi2_; }
    //! degree-to-radian conversion
    static ftype d2rad( const ftype& x );
    //! degree-to-radian conversion
    static ftype rad2d( const ftype& x );

  private:
    static float  nanf_;  //!< float NaN
    static double nand_;  //!< double NaN
    static ftype  nan_;   //!< ftype nan
    static ftype onepi_;  //!< one*pi
    static ftype twopi_;  //!< two*pi
    static ftype twopi2_; //!< two*pi*pi
    static ftype eightpi2_; //!< eight*pi*pi
    static ftype d2rad_;  //!< degree-radian conversion
    static ftype sim_a;   //!< sim fn param
    static ftype sim_b;   //!< sim fn param
    static ftype sim_c;   //!< sim fn param
    static ftype sim_d;   //!< sim fn param
    static ftype sim_e;   //!< sim fn param
    static ftype sim_A;   //!< invsim fn param
    static ftype sim_B;   //!< invsim fn param
    static ftype sim_C;   //!< invsim fn param
    static ftype sim_g;   //!< invsim fn param
    static ftype sim_p;   //!< invsim fn param
    static ftype sim_q;   //!< invsim fn param
    static ftype sim_r;   //!< invsim fn param
  };

} // namespace clipper

#endif
