/*!
 * \file
 * \brief Error functions - header file
 * \author Tony Ottosson and Adam Piatyszek
 *
 * -------------------------------------------------------------------------
 *
 * IT++ - C++ library of mathematical, signal processing, speech processing,
 *        and communications classes and functions
 *
 * Copyright (C) 1995-2010  (see AUTHORS file for a list of contributors)
 *
 * This program 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 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 *
 * -------------------------------------------------------------------------
 */

#ifndef ERROR_H
#define ERROR_H

#ifndef _MSC_VER
#  include <itpp/config.h>
#else
#  include <itpp/config_msvc.h>
#endif

#include <itpp/base/help_functions.h>


//!\addtogroup errorfunc
//!@{

#ifndef HAVE_ERF
//! \brief Error function
double erf(double x);
#endif

#ifndef HAVE_ERFC
//! Complementary error function
double erfc(double x);
#endif

//!@}


namespace itpp
{

//!\addtogroup errorfunc
//!@{

/*!
 * \brief Error function for complex argument
 * \author Adam Piatyszek
 *
 * This function calculates a well known error function \c erf(z)
 * for complex \c z. The implementation is based on unofficial
 * implementation for Octave. Here is a part of the author's note
 * from original sources:
 *
 * Put together by John Smith john at arrows dot demon dot co dot uk,
 * using ideas by others.
 *
 * Calculate \c erf(z) for complex \c z.
 * Three methods are implemented; which one is used depends on z.
 *
 * The code includes some hard coded constants that are intended to
 * give about 14 decimal places of accuracy. This is appropriate for
 * 64-bit floating point numbers.
 */
std::complex<double> erf(const std::complex<double>& z);

//! Inverse of error function
double erfinv(double x);

//! Q-function
double Qfunc(double x);


// ----------------------------------------------------------------------
// functions for matrices and vectors
// ----------------------------------------------------------------------

//! Error function
inline vec erf(const vec &x)
{
  return apply_function<double>(::erf, x);
}
//! Error function
inline mat erf(const mat &x)
{
  return apply_function<double>(::erf, x);
}
//! Error function
inline cvec erf(const cvec &x)
{
  return apply_function<std::complex<double> >(erf, x);
}
//! Error function
inline cmat erf(const cmat &x)
{
  return apply_function<std::complex<double> >(erf, x);
}

//! Inverse of error function
inline vec erfinv(const vec &x)
{
  return apply_function<double>(erfinv, x);
}
//! Inverse of error function
inline mat erfinv(const mat &x)
{
  return apply_function<double>(erfinv, x);
}

//! Complementary error function
inline vec erfc(const vec &x)
{
  return apply_function<double>(::erfc, x);
}
//! Complementary error function
inline mat erfc(const mat &x)
{
  return apply_function<double>(::erfc, x);
}

//! Q-function
inline vec Qfunc(const vec &x)
{
  return apply_function<double>(Qfunc, x);
}

//! Q-function
inline mat Qfunc(const mat &x)
{
  return apply_function<double>(Qfunc, x);
}
//!@}

} // namespace itpp

#endif // #ifndef ERROR_H




