c++ primer plus中的代码问题，求指教

//namespace.h
#include <string>

namespace pers
{
    struct Person
    {
        std::string fname;
        std::string lname;
    };

    void getPerson (Person &);
    void showPerson (Person &);
}

namespace debts
{
    using namespace pers;

    struct Debt
    {
        Person name;
        double amount;
    };

    void getDebt (Debt &);
    void showDebt (Debt &);
    double sumDebts (const Debt ar[],int n);
}

//namesp.cpp
#include <iostream>
#include "namespace.h"

namespace pers
{
    using std::cout;
    using std::cin;
    using std::endl;

    void getPerson (Person &rp)
    {
        cout << "Enter the first name  : ";
        cin >> rp.fname;
        cout << endl;

        cout << "Enter the last name : ";
        cin >> rp.lname;
        cout << endl;
    }

    void showPerson (const Person &rp)
    {
        cout << rp.lname << " and " << rp.fname;
        cout << endl;
    }
}

namespace debts
{
    using std::cout;
    using std::cin;
    using std::endl;
    using pers::getPerson;
    using pers::showPerson;


    void getDebt (Debt &rd)
    {
        getPerson (rd.name);
        cout << "Enter debt :";
        cin >> rd.amount;
    }

    void showDebt (const Debt &rd)
    {
        showPerson (rd.name);
        cout << " $" << rd.amount << endl;
    }

    double sumDebts (const Debt ar[],int n)
    {
        double total = 0;
        for (int i = 0;i < n;i++)
        {
            total += ar[i].amount;
        }

        return total;
    }
}

//main.cpp
#include <iostream>
#include "namespace.h"

void other (void);
void another (void);

int main ()
{
    using debts::Debt;
    using debts::showDebt;

    Debt golf = {{"Benny","Goatsniff"},120.0};
    showDebt (golf);
    other ();
    another ();
    return 0;
}

void other (void)
{
    using std :: cout;
    using std :: cin;
    using std :: endl;


    using namespace debts;

    Person dg = {"Doodles","Glister"};
    showPerson (dg);
   
    cout << endl;
    Debt zippy[3];

    int i = 0;
    for (i = 0;i < 3;i++)
    {
        getDebt (zippy[i]);
    }

    for (i = 0;i < 3;i++)
    {
        showDebt (zippy[i]);
    }

    cout << "Total debt : $" <<sumDebts (zippy,3) << endl;
    return ;
}

void another (void)
{
    using pers::Person;

    Person collector = {"Milo","Rightshitf"};
    pers::showPerson (collector);
    std::cout << std::endl;
   
    return ;
}