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Continuous Rand With Lagrange Interpolation (suck)

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  1. template<class Rand>
  2.   class ContinuousRandWithLagrangeInterpolation {
  3.   public:
  4.     int num;
  5.     double x_max;
  6.     Rand rand;
  7.     std::vector<double> x, f, den;
  8.     ContinuousRandWithLagrangeInterpolation(double _x_max, int _num):
  9.       rand(), x_max(_x_max), num(_num),
  10.       x(_num+1,0), f(_num+1,0), den(_num+1,0)
  11.     {
  12.       init();
  13.     }
  14.     void init(){
  15.       int i;
  16.       for(i=0;i<num+1;i++){
  17. 	x[i] = x_max/num*i;
  18. 	f[i] = rand();
  19.       }
  20.       for(i=0;i<num+1;i++){
  21. 	den[i] = mult(x[i], i);
  22.       }
  23.     }
  24.     double mult(const double& y, const int& j){
  25.       int i;
  26.       double m=1;
  27.       for(i=0;i<num+1;i++){
  28. 	if(i != j){
  29. 	  m *= ( y - x[i] );
  30. 	}
  31.       }
  32.       return m;
  33.     }
  34.     double operator()(const double& y) {
  35.       double p=0;
  36.       int i;
  37.       for(i=0;i<num+1;i++){
  38. 	p += f[i] * mult(y, i) / den[i];
  39.       }
  40.       return p;
  41.     }
  42.   };

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