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xmath.H

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#ifndef _XMATH_H
#define _XMATH_H



namespace xchen
{

  inline unsigned long int_pow(int base, int p)
  {
    unsigned long ret = 1;
    for(int i=0; i<p; i++)
      ret *= base;
    return ret;
  }

  const double pi = 3.141592;
  const double epsilon = 1.0E-5;

  extern double  epsilon_scaleup;
  extern double  epsilon_scaledown;

  //random int between low and high inclusive
#define irand48(low,high) ( (int) ((low) + ((high)-(low)+1) * drand48()))

  inline double lineFun(double a, double b, double c, double x, double y) { return (a*x+b*y+c); }

  inline double getYgivenX(double a, double b, double c, double x) { assert(b); return  -(a*x+c)/b; }
  inline double getXgivenY(double a, double b, double c, double y) { assert(a); return -(b*y+c)/a; }

  inline int lineFun(int a, int b, int c, int x, int y) { return (a*x+b*y+c); }
  inline int getYgivenX(int a, int b, int c, int x) { assert(b); return -(a*x+c)/b; }
  inline int getXgivenY(int a, int b, int c, int y) { assert(a); return -(b*y+c)/a; }

  inline int round(double a) { return (a>=0? int(a+.5) : int(a-.5)); }
  inline int sign(double num) { if(num>0) return 1; if(num<0) return -1; return 0; }

  inline long factorial(int n) 
  {
    if(!n) 
      return 1;
    else 
      return n * factorial(n-1);
  }



  template<class T>
  bool outside(const T& t, const T& t0, const T& t1) { return (t<t0 || t>t1); }

  inline bool approx_eq(double a, double b, double epsilon = 1.0E-6) { return fabs(a-b) < epsilon; }

  template<class T>
  inline double ratio(T v, T m, T M) { return (v-m)/(M-m); }

  template <class T>
  inline T interpolate(double t, const T& P1, const T& P2) { return P1*(1-t) + P2*t; }

  template <class T>
  inline T interpolate (double t, double t1, double t2, const T& p1, const T& p2) 
  {
    assert(t<=t2 && t>=t1 && t1!=t2);
    return ( (t2-t) * p1 + (t-t1) * p2 ) / (t2-t1);
  }



}//end namespace xchen


#endif

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