src/main/cpp/numerics4cpp/series/powerseries.h

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#ifndef _NUMERICS4CPP_SERIES_POWERSERIES_H_
#define _NUMERICS4CPP_SERIES_POWERSERIES_H_

#include <cmath>
#include "../iterativemethod.h"
#include "../exception/exception.h"

NUM_NAMESPACE_BEGIN

template<class Term>
class power_series : public iterative_method {

public:
        power_series(Term& t, unsigned int first = 0, unsigned int iterations = 100,
        double relative_error = 1.0e-13)
        : iterative_method(iterations, relative_error),
        _first_index(first), _term(t)
    {
        }
        
    ~power_series() {
    }

        double evaluate(double x) {
        unsigned int n = _first_index;
        double z = std::pow(x, (double)n);
        double t = _term(n) * z;
        double s = t;
        double sn = s;
        double error = std::numeric_limits<double>::infinity();
        
                do {
            ++n;
            z *= x;
            sn = s + (_term(n) * z);
            error = std::fabs(sn / s - 1.0);
                    s = sn;
        } while (n <= maximum_iterations() && error > maximum_relative_error());
        
                if (n > maximum_iterations()) {
                    throw convergence_exception("Power series failed to converge.");
                }
        
                return s;
        }
        
private:
    unsigned int _first_index;

    Term& _term;
};

typedef double power_series_term(unsigned int);

NUM_NAMESPACE_END

#endif

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