Operații de intrare/ieșire în C++. Clase și obiecte.

class NumeClasa {
  private:                      // implicit pentru class
    tip date_membre;            // accesibile doar din interiorul clasei

  public:
    NumeClasa();                // constructor implicit
    NumeClasa(parametri);       // constructor cu parametri
    ~NumeClasa();               // destructor

    tip functie_membra(...);    // interfata publica
};

class Temperatura {
  private:
    double celsius;

  public:
    // fara incapsulare, oricine ar putea scrie t.celsius = -500;
    bool setCelsius(double v) {
        if (v < -273.15) return false;    // validare: zero absolut
        celsius = v;
        return true;
    }
    double getCelsius() const { return celsius; }
    double getFahrenheit() const { return celsius * 9.0 / 5.0 + 32.0; }
};

#include <iostream>
#include <iomanip>
using namespace std;

int main()
{
    double pi = 3.14159265358979;

    cout << "Implicit:      " << pi << endl;
    cout << "fixed, 4 zec:  " << fixed << setprecision(4) << pi << endl;
    cout << "scientific:    " << scientific << pi << endl;

    cout << fixed << setprecision(2);

    // tabel aliniat
    cout << "\n" << left  << setw(14) << "Produs"
         << right << setw(8)  << "Buc"
         << setw(10) << "Pret" << endl;
    cout << setfill('-') << setw(32) << "" << setfill(' ') << endl;

    cout << left << setw(14) << "Rezistor"
         << right << setw(8) << 120 << setw(10) << 0.15 << endl;
    cout << left << setw(14) << "Condensator"
         << right << setw(8) << 45  << setw(10) << 0.80 << endl;

    // baze de numeratie
    int v = 255;
    cout << "\n" << dec << v << " = " << hex << v
         << " (hex) = " << oct << v << " (oct)" << dec << endl;

    cout << boolalpha << "\n3 > 5 este " << (3 > 5) << endl;

    return 0;
}

#include <iostream>
#include <string>
#include <iomanip>
using namespace std;

class Student {
  private:
    string nume;
    int    varsta;
    double medie;

  public:
    // constructor implicit
    Student() : nume("necunoscut"), varsta(0), medie(0.0) {
        cout << "  [constructor implicit]" << endl;
    }

    // constructor cu parametri, folosind lista de initializare
    Student(string n, int v, double m) : nume(n), varsta(v), medie(m) {
        cout << "  [constructor pentru " << nume << "]" << endl;
    }

    // constructor de copiere
    Student(const Student &alt)
        : nume(alt.nume), varsta(alt.varsta), medie(alt.medie) {
        cout << "  [copiere pentru " << nume << "]" << endl;
    }

    ~Student() {
        cout << "  [destructor pentru " << nume << "]" << endl;
    }

    // functii de acces, cu validare
    bool setMedie(double m) {
        if (m < 1.0 || m > 10.0) return false;
        medie = m;
        return true;
    }

    string getNume()  const { return nume; }
    double getMedie() const { return medie; }
    bool   promovat() const { return medie >= 5.0; }

    void afiseaza() const {
        cout << left << setw(18) << nume
             << right << setw(4) << varsta << " ani"
             << setw(8) << fixed << setprecision(2) << medie
             << "  " << (promovat() ? "promovat" : "restanta") << endl;
    }
};

int main()
{
    cout << "Creare obiecte:" << endl;
    Student s1("Popescu Ion", 20, 9.15);
    Student s2("Ionescu Maria", 21, 4.30);
    Student s3 = s1;                       // apeleaza constructorul de copiere

    cout << "\nLista:" << endl;
    s1.afiseaza();
    s2.afiseaza();
    s3.afiseaza();

    cout << "\nIncercare de setare a mediei la 15: ";
    cout << (s2.setMedie(15.0) ? "acceptat" : "RESPINS de validare") << endl;

    cout << "\nDistrugere (ordine inversa):" << endl;
    return 0;
}

#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main()
{
    // scriere
    {
        ofstream fout("date_cpp.txt");
        if (!fout) { cerr << "Nu pot scrie!" << endl; return 1; }

        fout << "Popescu Ion 20 9.15" << endl;
        fout << "Ionescu Maria 21 8.70" << endl;
    }   // fisierul se inchide AUTOMAT aici, prin destructor

    // citire
    ifstream fin("date_cpp.txt");
    if (!fin) { cerr << "Nu pot citi!" << endl; return 1; }

    string nume, prenume;
    int varsta;
    double medie;

    cout << "Continutul fisierului:" << endl;
    while (fin >> nume >> prenume >> varsta >> medie) {
        cout << "  " << nume << " " << prenume
             << ", " << varsta << " ani, media " << medie << endl;
    }
    fin.close();

    // citire linie cu linie
    ifstream f2("date_cpp.txt");
    string linie;
    int nr = 0;
    cout << "\nLinie cu linie:" << endl;
    while (getline(f2, linie)) {
        cout << "  " << ++nr << ": " << linie << endl;
    }

    return 0;
}