Algorithms.h

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//  ************************************************************************************************
//
//  BornAgain: simulate and fit reflection and scattering
//
//! @file      Base/Util/Algorithms.h
//! @brief     Defines and implements namespace BaseUtils::algo with some algorithms
//!
//! @homepage  http://www.bornagainproject.org
//! @license   GNU General Public License v3 or higher (see COPYING)
//! @copyright Forschungszentrum Jülich GmbH 2018
//! @authors   Scientific Computing Group at MLZ (see CITATION, AUTHORS)
//
//  ************************************************************************************************
 
#ifdef SWIG
#error no need to expose this header to Swig
#endif
 
#ifndef USER_API
#ifndef BORNAGAIN_BASE_UTIL_ALGORITHMS_H
#define BORNAGAIN_BASE_UTIL_ALGORITHMS_H
 
#include "Base/Util/Assert.h"
#include <algorithm>
#include <limits>
#include <vector>
 
//! Some additions to standard library algorithms.
 
namespace BaseUtils::algo {
 
//! Returns true if two doubles agree within machine epsilon.
inline bool almostEqual(double a, double b)
{
    constexpr double eps = std::numeric_limits<double>::epsilon();
    return std::abs(a - b) <= eps * std::max(eps, (std::abs(a) + std::abs(b)) / 2);
}
 
//! Returns the minimum value of function evaluate as applied to the elements of an iterator range.
template <typename Evaluator, typename Iterator>
double min_value(const Iterator& begin, const Iterator& end, const Evaluator& evaluate);
 
//! Returns the maximum value of function evaluate as applied to the elements of an iterator range.
template <typename Evaluator, typename Iterator>
double max_value(const Iterator& begin, const Iterator& end, const Evaluator& evaluate);
 
//! Returns the concatenation of two std::vector%s.
template <class T>
std::vector<T> concat(const std::vector<T>& v1, const std::vector<T>& v2);
 
} // namespace BaseUtils::algo
 
//  ************************************************************************************************
//  Implementation
//  ************************************************************************************************
 
template <typename Evaluator, typename Iterator>
double BaseUtils::algo::min_value(const Iterator& begin, const Iterator& end,
                                  const Evaluator& evaluate)
{
    ASSERT(begin != end);
    double result = evaluate(*begin);
    Iterator it = begin;
    while (++it != end)
        result = std::min(result, evaluate(*it));
    return result;
}
 
template <typename Evaluator, typename Iterator>
double BaseUtils::algo::max_value(const Iterator& begin, const Iterator& end,
                                  const Evaluator& evaluate)
{
    ASSERT(begin != end);
    double result = evaluate(*begin);
    Iterator it = begin;
    while (++it != end)
        result = std::max(result, evaluate(*it));
    return result;
}
 
template <class T>
std::vector<T> BaseUtils::algo::concat(const std::vector<T>& v1, const std::vector<T>& v2)
{
    std::vector<T> v = v1;
    v.insert(v.end(), v2.begin(), v2.end());
    return v;
}
 
#endif // BORNAGAIN_BASE_UTIL_ALGORITHMS_H
#endif // USER_API