Increase to Interest Rate and Interest Rate to Increase

#include <ctgmath>
#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <locale>

namespace jacknpoe {
//--------------------------- Interest class
    class Interest {
    protected:
    protected:
        short Quant;        // number of payments (all payments with 0 will be considered a valid payment in cash)
        bool Compounded;        // compounded (InterestRate², InterestRate³)
        short Period;       // period fot the InterestRate (like 30 for a 30 days interest rate)
        short *Payments;        // payment days in periods like in days { 0, 30, 60, 90}
        long double *Weights;       // payment weights (in any unit, value, apportionment...)
        void init( short quant, bool compounded, short period);
    public:
        Interest( short quant = 0, bool compounded = false, short period = 30);
        Interest( bool compounded, short period = 30);
        ~Interest();
        bool setQuant( short quant);
        short getQuant( void);
        void setCompounded( bool compounded);
        bool getCompounded( void);
        bool setPeriod( short period);
        short getPeriod( void);
        bool setPayment( short index, short value);
        short getPayment( short index);
        bool setWeight( short index, long double value);
        long double getWeight( short index);
        long double getTotalWeight( void);
        long double InterestRateToIncrease( long double interestrate);
        long double IncreaseToInterestRate( long double increase, char precision = 8,
                                            short maxiterations = 100, long double maxinterestrate = 50,
                                            bool increaseasoriginalvalue = false);
    };

    void Interest::init( short quant, bool compounded, short period) {
        Payments = NULL;  Weights = NULL;  Quant = 0;
        setQuant( quant);  Compounded = compounded;  Period = period;
    }

    Interest::Interest( short quant, bool compounded, short period) { init( quant, compounded, period); }
    Interest::Interest( bool compounded, short period) { init( 0, compounded, period); }

    bool Interest::setQuant( short quant) {
        if( quant < 0 ) return false; if( quant == Quant) return true;
        Payments = (short *) std::realloc( Payments, sizeof( short) * quant);
        if( quant !=0 and Payments == NULL) { Quant = 0; return false; }
        Weights = (long double *) std::realloc( Weights, sizeof( long double) * quant);
        if( quant !=0 and Weights == NULL) { std::free( Payments); Payments = NULL; Quant = 0; return false; }
        for( short index = Quant; index < quant; index++) { Payments[ index] = 0; Weights[ index] = 1; }
        Quant = quant; return true;
    }
    short Interest::getQuant( void) { return Quant; }

    void Interest::setCompounded( bool compounded) { Compounded = compounded; }
    bool Interest::getCompounded( void) { return Compounded; }

    bool Interest::setPeriod( short period) {
        if( period < 1 ) return false;
        Period = period; return true;
    }
    short Interest::getPeriod( void) { return Period; }

    bool Interest::setPayment( short index, short value) {
        if( index < 0 or index >= Quant or value < 0) return false;
        Payments[ index] = value; return true;
    }
    short Interest::getPayment( short index) {
        if( index < 0 or index >= Quant) return 0; else return Payments[ index];
    }

    bool Interest::setWeight( short index, long double value) {
        if( index < 0 or index >= Quant or value < 0) return false;
        Weights[ index] = value; return true;
    }
    long double Interest::getWeight( short index) {
        if( index < 0 or index >= Quant) return 0; else return Weights[ index];
    }

    long double Interest::getTotalWeight( void) {
        long double accumulator = 0;
        for( short index = 0; index < Quant; index++) accumulator += Weights[ index];
        return accumulator;
    }

    long double Interest::InterestRateToIncrease( long double interestrate) {
        if( interestrate <= 0 or Quant == 0 ) return 0;
        long double total = getTotalWeight();
        if( total == 0) return 0;
        if( Period <= 0) return 0;
        long double accumulator = 0; bool onlyzero = true;

        for( short index = 0; index < Quant; index++) {
            if( Payments[ index] > 0 and Weights[ index] > 0) onlyzero = false;
            if( Compounded)     // compounded interest
                accumulator += Weights[ index] / pow( 1 + interestrate / 100, Payments[ index] / Period);
            else        // simple interest
                accumulator += Weights[ index] / (( 1 + interestrate / 100) * Payments[ index] / Period);
        }
        if( onlyzero) return 0;
        return ( total / accumulator - 1 ) * 100;
    }

    long double Interest::IncreaseToInterestRate( long double increase, char precision,
                                                  short maxiterations, long double maxinterestrate,
                                                  bool increaseasoriginalvalue)
    {
        long double mininterestrate = 0, medinterestrate, min_diff;
        if( maxiterations < 1 or Quant == 0) return 0;
        if( precision < 1) return 0;
        long double total = getTotalWeight();
        if( total == 0) return 0;
        if( Period <= 0) return 0;
        if( increase <= 0) return 0;
        if( increaseasoriginalvalue) {
            increase = 100 * ( total / increase - 1 );
            if( increase <= 0) return 0;
        }

        min_diff = pow( 0.1, precision);
        for( short index = 0; index < maxiterations; index++) {
            medinterestrate = ( mininterestrate + maxinterestrate) / 2;
            if( ( maxinterestrate - mininterestrate ) < min_diff) break;        // the desired precision was reached
            if( InterestRateToIncrease( medinterestrate ) <= increase )
                mininterestrate = medinterestrate;
            else
                maxinterestrate = medinterestrate;
        }
        return medinterestrate;
    }

    Interest::~Interest() { std::free( Payments); std::free( Weights); }
}

using namespace jacknpoe;   // this code is awkward because, in reality, this file is a concatenation of a .h and a .cpp (from a library) and the main
int main() {
    Interest interest;

    setlocale( LC_ALL, "");     // equal caracters in prompt
    std::cout.precision(9);

    short payments, temp, period, option;
    long double increase, interestrate, total, temp_ld;


    while( true) {
        std::cout << "——————————————————————————————————\n";
        std::cout << "| Choose an option               |\n";
        std::cout << "——————————————————————————————————\n\n";
        std::cout << "     1. Interest Rate to Increase.\n\n";
        std::cout << "     2. Increase to Interest Rate.\n\n";
        std::cout << "Others. Exit.\n\n\n";

        std::cin >> option;
        std::cout << "\n";
        if( option != 1 and option != 2) {
            break;
        }

        std::cout << "\n";

        std::cout << "Number of payments: ";
        std::cin >> payments;

        if( payments < 1) {
            std::cout << "You must provide at least one payment.\n\n";
            system( "PAUSE");
            std::cout << "\n\n";
            continue;
        }
        interest.setQuant( payments);

        std::cout << "Interest rate relating to (example: 30 days, 1 month): ";
        std::cin >> period;

        if( period < 1) {
            std::cout << "Interest rate must relating to at least one period.\n\n";
            system( "PAUSE");
            std::cout << "\n\n";
            continue;
        }
        interest.setPeriod( period);

        for( short index = 0; index < payments; index++) {
            std::cout << "Payment " << index + 1 << ": ";
            std::cin >> temp;
            interest.setPayment( index, temp);

            std::cout << "Weight " << index + 1 << ": ";
            std::cin >> temp_ld;
            interest.setWeight( index, temp_ld);
        }

        if( option == 1)
        {
            std::cout << "\nFull cash value: ";
            std::cin >> total;

            std::cout << "Interest rate: ";
            std::cin >> interestrate;

            interest.setCompounded( false); // simple interest
            increase = interest.InterestRateToIncrease( interestrate);
            std::cout << "\n\nSIMPLE INTEREST";
            std::cout << "\nIncrease: " << increase << "%, payment value: " << total * ( 1 + increase / 100) / payments;
            std::cout << ", total paid: " << total * ( 1 + increase / 100);

            interest.setCompounded( true);  // compound interest
            increase = interest.InterestRateToIncrease( interestrate);
            std::cout << "\n\nCOMPOUND INTEREST";
            std::cout << "\nIncrease: " << increase << "%, payment value: " << total * ( 1 + increase / 100) / payments;
            std::cout << ", total paid: " << total * ( 1 + increase / 100);
        }
            else
        {
            std::cout << "\nIncrease: ";
            std::cin >> increase;

            interest.setCompounded( false);
            interestrate = interest.IncreaseToInterestRate( increase);
            std::cout << "\n\nSIMPLE INTEREST: " << interestrate;

            interest.setCompounded( true);
            interestrate = interest.IncreaseToInterestRate( increase);
            std::cout << "\n\nCOMPOUND INTEREST: " << interestrate;
        }

        std::cout << "\n\n";
        system( "PAUSE");
        std::cout << "\n\n";
    }
    std::cout << "\n\n"; exit( 0);
}

//
//----------------------------------
//| Choose an option               |
//----------------------------------
//     1. Interest Rate to Increase.
//     2. Increase to Interest Rate.
//Others. Exit.

//2

//Number of payments: 3
//Interest rate relating to (example: 30 days, 1 month): 30
//Payment 1: 30
//Weight 1: 1
//Payment 2: 60
//Weight 2: 1
//Payment 3: 90
//Weight 3: 1

//Increase: 20

//SIMPLE INTEREST: 10.2936087
//COMPOUND INTEREST: 9.70102574

//----------------------------------
//| Choose an option               |
//----------------------------------
//     1. Interest Rate to Increase.
//     2. Increase to Interest Rate.
//Others. Exit.

//1

//Number of payments: 2
//Interest rate relating to (example: 30 days, 1 month): 1
//Payment 1: 1
//Weight 1: 1
//Payment 2: 2
//Weight 2: 1

//Full cash value: 1000
//Interest rate: 5

//SIMPLE INTEREST
//Increase: 7.44186047%, payment value: 537.209302, total paid: 1074.4186

//COMPOUND INTEREST
//Increase: 7.56097561%, payment value: 537.804878, total paid: 1075.60976