====== 12 - Úvod do C++ ======

===== 1. Jmenné prostory, vstup a výstup =====

<code c++>
#include  <stdio.h>    // C include, /usr/include, /usr/local/include

#include  <iostream>

namespace test
{
    int a = 10;    // test::a
    int b = 78;
}

using namespace std;
using namespace test;

int main()
{
    printf ("ahoj C\n");

    std::cout << "ahoj C++" << std::endl;

    std::cout << "jedna" << " dva" << " tri" << std::endl;

    std::cout << "10 + 30 = " << 10 + 30 << std::endl;

    int a = 33;

    std::cout << "a = " << a << ", test::a = " << test::a << std::endl;
   
    cout << "a = " << a << ", test::a = " << test::a << endl;
   
    cout << "b = " << b << endl;

    /*
        std::cout     std. vystup
        std::cin      std. vstup
        std::cerr     std. chybovy vystup
        std::clog     std. logovaci vystup
    */

    cout << "zadej cislo datoveho typu int: ";

    cin >> b;

    if (cin.good())
        cout << "zadal jsi " << b << endl;
    else
        cout << "nauc se datove typy" << endl;

    return 0;
}
</code>

===== 2. Vstup a výstup - formátování, modifikátory =====

<code c++>
#include <iostream>
#include <iomanip>

using namespace std;

int main()
{
	float pi = 3.14159265;
	float pp = 65.876866;
	float px = 768748.898;

	cout << pi << endl << pp << endl << px << endl;

	cout << setprecision(2);	

	cout << pi << endl << pp << endl << px << endl;

	cout << fixed;

	cout << "fixed: " << endl << pi << endl << pp << endl << px << endl;

	cout << setprecision(5);

	cout << pi << endl << pp << endl << px << endl;

	cout << scientific;

	cout << pi << endl << pp << endl << px << endl;

	cout.unsetf (ios_base::floatfield);

	cout << pi << endl << pp << endl << px << endl;

	cout << setw(15) << pi << endl;

	return 0;
}
</code>

===== 3. Reference =====

<code c++>
#include <iostream>

void f1(int *a) 
{
	*a = 31;
}

void f2(int &a) 
{
	a = 32;	
}

int main()
{
    int x = 10;

    std::cout << "x = " << x << std::endl;

    f1 (&x);

    std::cout << "x = " << x << std::endl;

    int &y = x;
	
    f2 (x);

    std::cout << "x = " << x << std::endl;

    return 0;
}
</code>

===== 4. Jednoduchá práce se souborem =====

<code c++>

#include <iostream>
#include <fstream>

using namespace std;

int main ()
{
	ifstream in ("04.cpp");
	ofstream out ("04-copy.cpp");

	if (in.good ())
	{
		cout << "soubor byl otevren" << endl;

		string s;
			
		while (getline (in, s))
		{
			cout << s << endl;
			out << s << endl;
		}
	}

	return 0;
}
</code>