PolLeg.cpp

Go to the documentation of this file.

#include "wcpplib/math/PolLeg.h"
#include "wcpplib/util/FunNameStack.h"
/*
Copyright (c) 2003 I. B. Smirnov
 
Permission to use, copy, modify, distribute and sell this file
and its documentation for any purpose is hereby granted without fee,
provided that the above copyright notice, this permission notice,
and notices about any modifications of the original text
appear in all copies and in supporting documentation.
It is provided "as is" without express or implied warranty.
*/
 
double polleg(int l, double x) {
  mfunname("double polleg(int l, double x)");
  check_econd11(l, < 0, mcerr);
  check_econd11a(l, > 6, "not implemented", mcerr);
  switch (l) {
    case 0:
      return 1.0;
    case 1:
      return x;
    case 2:
      return 0.5 * (3.0 * x * x - 1.0);
    case 3:
      return 0.5 * (5.0 * x * x * x - 3.0 * x);
    case 4: {
      double x2 = x * x;
      return 1.0 / 8.0 * (35.0 * x2 * x2 - 30.0 * x2 + 3.0);
    }
    case 5: {
      double x2 = x * x;
      double x3 = x2 * x;
      return 1.0 / 8.0 * (63.0 * x3 * x2 - 70.0 * x3 + 15.0 * x);
    }
    case 6: {
      double x2 = x * x;
      double x4 = x2 * x2;
      return 1.0 / 16.0 * (231.0 * x4 * x2 - 315.0 * x4 + 105.0 * x2 - 5.0);
    }
    default:
      return 0.0;
  }
  /*
  if( l == 0 )
    return 1.0;
  else if(l == 1)
    return x;
  else if(l == 2)
    return 0.5 * (3.0 * x * x - 1.0);
  return 0.0;  // should never happen
  */
}