/*
* Copyright (c) 2015-2019 Sergey Bakhurin
* Digital Signal Processing Library [http://dsplib.org]
*
* This file is part of DSPL.
*
* is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* DSPL is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Foobar.  If not, see <http://www.gnu.org/licenses/>.
*/


#include <stdio.h>
#include <stdlib.h>
#include "dspl.h"


/******************************************************************************
Numerical integration of real data using the trapezoidal method.
*******************************************************************************/
int DSPL_API trapint(double* x, double* y, int n, double* sum)
{
  int k;

  if(!x || !y)
    return ERROR_PTR;
  if(n<2)
    return ERROR_SIZE;
  *sum = 0.0;

  for(k = 1; k < n; k++)
    *sum += 0.5 * (x[k] - x[k-1]) * (y[k] + y[k-1]);

  return RES_OK;
}




/*******************************************************************************
Numerical integration of complex data using the trapezoidal method.
*******************************************************************************/
int DSPL_API trapint_cmplx(double* x, complex_t* y, int n, complex_t* sum)
{

  int k;
  double dx;
  if(!x || !y)
    return ERROR_PTR;
  if(n<2)
    return ERROR_SIZE;
  RE(*sum) = IM(*sum) = 0.0;

  for(k = 1; k < n; k++)
  {
    dx = 0.5 * (x[k] - x[k-1]);
    RE(*sum) +=  dx * (RE(y[k]) + RE(y[k-1]));
    IM(*sum) +=  dx * (IM(y[k]) + IM(y[k-1]));
  }
  return RES_OK;
}