C ++ Programming Languages

1. Sharif University of Technology C++ Programming Languages Lecturer: OmidJafarinezhad Fall 2013 Lecture 2 Department of Computer Engineering

2. Extensions to C #include <stdio.h> voidshow(intval) { printf("Integer: %d\n", val); } voidshow(doubleval) { printf("Double: %lf\n", val); } voidshow(char const *val) { printf("String: %s\n", val); } int main() { show(12); show(3.1415); show("Hello World!\n"); } Function Overloading

3. Extensions to C • Function Overloading: • Do not use function overloading for functions doing conceptually different tasks. • C++ does not allow identically named functions to differ only in their return values.

4. Extensions to C #include <stdio.h> int Sum(int a = 1, int b = 4) {return a + b;} int main() { printf("%d", Sum()); // arguments: 1 + 4 printf("%d”, Sum(20)); // arguments: 20 + 4 printf("%d", Sum(20, 5)); // arguments: 20 + 5 // Sum(,6); // Error } Default function arguments

5. Extensions to C // sample header file extern void two_ints(int a = 1, int b = 4); // code of function in, filename.ccp voidtwo_ints(int a, int b) { ... } • Default function arguments • Default arguments must be known at compile-time since at that moment arguments are supplied to functions. Therefore, the default arguments must be mentioned at the function's declaration, rather than at its implementation:

6. Extensions to C #include <iostream> using namespace std; int main() { intival; charsval[30]; std::cout<< "Enter a number:\n"; // <<, insertion operator cin >> ival; // >>, extraction operator cout << "And now a string:\n"; cin >> sval; cout<< "The number is: " << ival << "\n" "And the string is: " << sval << '\n'; }

7. Extensions to C // c++ intint_value; int &ref = int_value; ++int_value; ++ref; // c and c++ intint_value; int *ref = &int_value; ++int_value; ++(*ref); • References • the reference operator & indicates that ref is not itself an int but a reference to one • synonyms for variables • A reference to a variable is like an alias

8. Extensions to C // c++ void increase(int&valr) { valr += 5; } int main() { int x; increase(x); } // c and c++ void increase(int *valp) { *valp += 5; } int main() { int x; increase(&x); } • References

9. Extensions to C boolbValue; // true (!=0) or false (0) bool bValue1 = true; // explicit assignment bool bValue2(false); // implicit assignment bool bValue1 = !true; // bValue1 will have the value false bool bValue2(!false); // bValue2 will have the value true boolbValue = true; // boolbValue = 30; cout << bValue << endl; // 1 cout << !bValue << std::endl; // 0 if (!bValue) cout << "The if statement was true" << endl; else cout << "The if statement was false" << endl; Bool

10. IOStreams • File • ifstream (derived from istream) • file input • ofstream (derived from ostream) • output file • fstream(derived from iostream). • input/output file • fstream.h

11. IOStreams #include <fstream> #include <iostream> // ofstream is used for writing files. // We'll make a file called Sample.dat ofstreamoutf("Sample.dat"); // If we couldn't open the output file stream for writing if (!outf)// Print an error and exit     {   …  }  // We'll write two lines into this file outf << "This is line 1" << endl; outf << "This is line 2" << endl; File output

12. IOStreams #include <fstream> #include <iostream> // ifstream is used for reading files     // We'll read from a file called Sample.dat ifstreaminf("Sample.dat"); // If we couldn't open the output file stream for writing if (!inf)// Print an error and exit     {   …  } // While there's still stuff left to read     while (inf)     { // read stuff from the file into a string and print it std::string strInput; inf >> strInput; getline(inf, strInput); cout << strInput << endl;     } • Output File • ifstream returns a 0 if we’ve reached the end of the file (EOF)