legndr.cpp

来自「c++的数学物理方程数值算法源程序。这是"Numerical Methods f」· C++ 代码 · 共 20 行

#include "NumMeth.h"

void legndr( int n, double x, Matrix& p) {
// Legendre polynomials function
// Inputs  
//    n    Highest order polynomial returned
//    x    Value at which polynomial is evaluated
// Output
//    p    Vector containing P(x) for order 0,1,...,n

  //* Perform upward recursion
  p(1) = 1;      // P(x) for n=0
  if(n == 0) return;
  p(2) = x;      // P(x) for n=1
  // Use upward recursion to obtain other n's
  int i;
  for( i=3; i<=(n+1); i++ )  
    p(i) = ((2*i-3)*x*p(i-1) - (i-2)*p(i-2))/(i-1);
}