====== 12 - Úvod do C++ ======
===== 1. Jmenné prostory, vstup a výstup =====
#include // C include, /usr/include, /usr/local/include
#include
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;
}
===== 2. Vstup a výstup - formátování, modifikátory =====
#include
#include
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;
}
===== 3. Reference =====
#include
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;
}
===== 4. Jednoduchá práce se souborem =====
#include
#include
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;
}