# include <cmath>
# include <cstdlib>

using namespace std;

# include "dirichlet.hpp"

//****************************************************************************80

double dirichlet ( double x, int n )

//****************************************************************************80
//
//  Purpose:
//
//    dirichlet() evaluates the Dirichlet kernel function.
//
//  Discussion:
//
//    The Dirichlet kernel function is also called the periodic sinc function.
//
//  Licensing:
//
//    This code is distributed under the MIT license.
//
//  Modified:
//
//    13 July 2025
//
//  Author:
//
//    John Burkardt
//
//  Input:
//
//    real x: the argument of the function.
//
//    integer n: the degree of the function.
//
//  Output:
//
//    real dirichlet: the value of the function.
//
{
  double value;

  if ( sin ( 0.5 * x ) == 0.0 )
  {
    value = 1.0;
  }
  else
  {
    value = sin ( 0.5 * n * x ) / n / sin ( 0.5 * x );
  }

  return value;
}