# include <cstdlib>
# include <ctime>
# include <fstream>
# include <iomanip>
# include <iostream>

using namespace std;

# include "sine_integral.hpp"

int main ( );
void si_plot ( );
double *r8vec_linspace_new ( int n, double a_first, double a_last );
void si_test ( );
void si_values ( int &n_data, double &x, double &fx );
void timestamp ( );

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

int main ( )

//****************************************************************************80
//
//  Purpose:
//
//    sine_integral_test() tests sine_integral().
//
//  Licensing:
//
//    This code is distributed under the MIT license.
//
//  Modified:
//
//    10 August 2025
//
//  Author:
//
//    John Burkardt
//
{
  timestamp ( );
  cout << "\n";
  cout << "sine_integral_test():\n";
  cout << "  C++ version\n";
  cout << "  Test sine_integral().\n";

  si_plot ( );
  si_test ( );
//
//  Terminate.
//
  cout << "\n";
  cout << "sine_integral_test():\n";
  cout << "  Normal end of execution.\n";
  cout << "\n";
  timestamp ( );

  return 0;
}
//****************************************************************************80

void si_plot (  )

//****************************************************************************80
//
//  Purpose:
//
//    si_plot() plots si(x).
//
//  Licensing:
//
//    This code is distributed under the MIT license.
//
//  Modified:
//
//    10 August 2025
//
//  Author:
//
//    John Burkardt
//
{
  string command_filename;
  ofstream command_unit;
  string data_filename;
  ofstream data_unit;
  int i;
  int nplot;
  string output_filename;
  string prefix = "si";
  double *xplot;
  double *yplot;

  nplot = 101;
  xplot = r8vec_linspace_new ( nplot, -10.0, +10.0 );
  yplot = new double[nplot];

  for ( i = 0; i < nplot; i++ )
  {
    yplot[i] = si ( xplot[i] );
  }
//
//  Create the data file.
//
  data_filename = prefix + "_data.txt";
  data_unit.open ( data_filename.c_str ( ) );
  for ( i = 0; i < nplot; i++ )
  {
    data_unit << xplot[i] << "  " << yplot[i] << "\n";
  }
  data_unit.close ( );
  cout << "\n";
  cout << "  Created graphics data file '" << data_filename << "'.\n";
//
//  Plot the selected data.
//
  command_filename = prefix + "_commands.txt";
  command_unit.open ( command_filename.c_str ( ) );

  command_unit << "# " << command_filename << "\n";
  command_unit << "#\n";
  command_unit << "# Usage:\n";
  command_unit << "#  gnuplot < " << command_filename << "\n";
  command_unit << "#\n";
  command_unit << "set term png\n";
  command_unit << "set nokey\n";
  output_filename = prefix + "_plot.png";
  command_unit << "set output '" << output_filename << "'\n";
  command_unit << "set xlabel '<---X--->'\n";
  command_unit << "set ylabel '<---Si(X)--->'\n";
  command_unit << "set title 'Sine Integral Si(x)'\n";
  command_unit << "set grid\n";
  command_unit << "set style data lines\n";
  command_unit << "plot '" << data_filename << "' using 1:2 lw 3 linecolor rgb 'blue'\n";

  command_unit.close ( );
  cout << "  Created graphics command file '" << command_filename<< "'.\n";

  delete [] xplot;
  delete [] yplot;

  return;
}
//****************************************************************************80

double *r8vec_linspace_new ( int n, double a_first, double a_last )

//****************************************************************************80
//
//  Purpose:
//
//    r8vec_linspace_new() creates a vector of linearly spaced values.
//
//  Discussion:
//
//    An R8VEC is a vector of R8's.
//
//    4 points evenly spaced between 0 and 12 will yield 0, 4, 8, 12.
//
//    In other words, the interval is divided into N-1 even subintervals,
//    and the endpoints of intervals are used as the points.
//
//  Licensing:
//
//    This code is distributed under the MIT license.
//
//  Modified:
//
//    29 March 2011
//
//  Author:
//
//    John Burkardt
//
//  Input:
//
//    int N, the number of entries in the vector.
//
//    double A_FIRST, A_LAST, the first and last entries.
//
//  Output:
//
//    double R8VEC_LINSPACE_NEW[N], a vector of linearly spaced data.
//
{
  double *a;
  int i;

  a = new double[n];

  if ( n == 1 )
  {
    a[0] = ( a_first + a_last ) / 2.0;
  }
  else
  {
    for ( i = 0; i < n; i++ )
    {
      a[i] = ( ( double ) ( n - 1 - i ) * a_first 
             + ( double ) (         i ) * a_last ) 
             / ( double ) ( n - 1     );
    }
  }
  return a;
}
//****************************************************************************80

void si_test ( )

//****************************************************************************80
//
//  Purpose:
//
//    si_test() tests si().
//
//  Licensing:
//
//    This code is distributed under the MIT license.
//
//  Modified:
//
//    10 August 2025
//
//  Author:
//
//    John Burkardt
//
{
  double fx1;
  double fx2;
  int n_data;
  double x;

  cout << "\n";
  cout << "si_test():\n";
  cout << "  si() evaluates the sine integral function.\n";
  cout << "\n";
  cout << "      X            SI(X)\n";
  cout << "\n";

  n_data = 0;

  while ( true )
  {
    si_values ( n_data, x, fx1 );

    if ( n_data == 0 )
    {
      break;
    }

    fx2 = si ( x );

    cout << "  " << setw(14) << x
         << "  " << setw(24) << setprecision ( 16 ) << fx1
         << "  " << setw(24) << setprecision ( 16 ) << fx2 << "\n";
  }

  return;
}
//****************************************************************************80

void si_values ( int &n_data, double &x, double &fx )

//****************************************************************************80
//
//  Purpose:
//
//    si_values() returns some values of the sine integral function.
//
//  Discussion:
//
//    SI(X) = integral ( 0 <= T <= X ) sin ( T ) / T dt
//
//    In Mathematica, the function can be evaluated by:
//
//      SinIntegral[x]
//
//  Licensing:
//
//    This code is distributed under the MIT license.
//
//  Modified:
//
//    12 August 2004
//
//  Author:
//
//    John Burkardt
//
//  Reference:
//
//    Milton Abramowitz, Irene Stegun,
//    Handbook of Mathematical Functions,
//    National Bureau of Standards, 1964,
//    ISBN: 0-486-61272-4,
//    LC: QA47.A34.
//
//    Stephen Wolfram,
//    The Mathematica Book,
//    Fourth Edition,
//    Cambridge University Press, 1999,
//    ISBN: 0-521-64314-7,
//    LC: QA76.95.W65.
//
//  Parameters:
//
//    Input/output, int &N_DATA.  The user sets N_DATA to 0 before the
//    first call.  On each call, the routine increments N_DATA by 1, and
//    returns the corresponding data; when there is no more data, the
//    output value of N_DATA will be 0 again.
//
//    Output, double &X, the argument of the function.
//
//    Output, double &FX, the value of the function.
//
{
# define N_MAX 16

  static double fx_vec[N_MAX] = {
     0.4931074180430667E+00,
     0.5881288096080801E+00,
     0.6812222391166113E+00,
     0.7720957854819966E+00,
     0.8604707107452929E+00,
     0.9460830703671830E+00,
     0.1108047199013719E+01,
     0.1256226732779218E+01,
     0.1389180485870438E+01,
     0.1505816780255579E+01,
     0.1605412976802695E+01,
     0.1778520173443827E+01,
     0.1848652527999468E+01,
     0.1833125398665997E+01,
     0.1758203138949053E+01,
     0.1654140414379244E+01 };

  static double x_vec[N_MAX] = {
      0.5E+00,
      0.6E+00,
      0.7E+00,
      0.8E+00,
      0.9E+00,
      1.0E+00,
      1.2E+00,
      1.4E+00,
      1.6E+00,
      1.8E+00,
      2.0E+00,
      2.5E+00,
      3.0E+00,
      3.5E+00,
      4.0E+00,
      4.5E+00 };

  if ( n_data < 0 )
  {
    n_data = 0;
  }

  n_data = n_data + 1;

  if ( N_MAX < n_data )
  {
    n_data = 0;
    x = 0.0;
    fx = 0.0;
  }
  else
  {
    x = x_vec[n_data-1];
    fx = fx_vec[n_data-1];
  }

  return;
# undef N_MAX
}
//****************************************************************************80

void timestamp ( )

//****************************************************************************80
//
//  Purpose:
//
//    timestamp() prints the current YMDHMS date as a time stamp.
//
//  Example:
//
//    31 May 2001 09:45:54 AM
//
//  Licensing:
//
//    This code is distributed under the MIT license. 
//
//  Modified:
//
//    19 March 2018
//
//  Author:
//
//    John Burkardt
//
{
# define TIME_SIZE 40

  static char time_buffer[TIME_SIZE];
  const struct std::tm *tm_ptr;
  std::time_t now;

  now = std::time ( NULL );
  tm_ptr = std::localtime ( &now );

  std::strftime ( time_buffer, TIME_SIZE, "%d %B %Y %I:%M:%S %p", tm_ptr );

  std::cout << time_buffer << "\n";

  return;
# undef TIME_SIZE
}