1. Output Stream Formatting
Andy Wang
Object Oriented Programming in C++
COP 3330

2. Brief Introduction cout is the standard output stream
It is of type ostream
cin is the standard input stream
It is of type istream
ostream and istream are classes

3. Stream member functions
setf() // the set flags function
Takes a parameter to turn the flag on
ios::fixed // print floating numbers in fixed notation
// digits before and after the ‘.’
ios::scientific // print floating numbers in scientific (exponential) notation
ios::showpoint // decimal point will always be printed for floating point types (e.g., 4.0)

4. Stream member functions
setf() // the set flags function
ios::right // right justifies an output item in a field
// if field width is specified
ios::left // left justifies an output item in a field
ios::showbase // show a leading 0 for octal, 0x for hex

5. Stream member functions
unsetf() // unset flags
precision() // specifies the number of digits after the decimal point

6. Stream member functions
width() // specify the field width for the next item
// extra space will be filled with the fill character
int x = 1234;
cout.setf(io::right);
cout.width(10);
cout << “Hello”;
cout.width(15);
cout << x;
// output of the above is:
// Hello

7. Stream member functions
fill() // specify the fill character to pad out the extra space in a field when used with width
int x = 1234;
cout.setf(io::right);
cout.fill(‘.’);
cout.width(10);
cout << x;
// output of the above is: //

8. Stream Manipulators
A stream manipulator is a symbol or function that is used by placing it on the right side of the insertion operator <<. Need to include <iomanip>
A plain manipulator is just a symbol
cout << endl; // endl is a stream manipulator
A parameterized stream manipulator looks like a function call
cout << setw(10);

9. Stream Manipulators
Many of the stream manipulators are alternative ways of doing tasks performed by member function
Good for cascading
cout << setw(10) << “Hello” << endl;
setprecision() ~= precision()
cout.precision(2);
cout << setprecision(2);

10. Stream Manipulators setw() ~= width() setfill() ~= fill()
cout.width(10);
cout << setw(10);
setfill() ~= fill()
cout.fill(‘*’);
cout. << setfill(‘*’);
setiosflags() ~= setf()
cout.setf(ios::left);
cout << setiosflags(ios::left);
setbase()
// set to base 10, 8, or 16

11. Example: Formatting Flags and Member Functions
amio/format/formats1.cpp

12. format1.cpp
#include <iostream> using namespace std; void PrintData(int x, double y) { cout.width(15); cout << x; cout.width(25); cout << y; cout.width(30); cout << “Hello, World” << endl; }

13. format1.cpp
int main() { int a; double b; cout << “Enter an integer: “; cin >> a; cout << “Enter a double: “; cin >> b; cout << endl; PrintData(a, b); cout.setf(ios::fixed); cout.setf(ios::showpoint); cout.setf(ios::left); cout.precision(5);

14. format1.cpp
cout.setf(ios::scientific); cout.setf(ios::right); cout.precision(1); PrintData(a, b); cout.setf(ios::showpo); cout.fill(‘.’); Print(a, b); cout << “\nSee ya!\n”; }

15. Example: Stream Manipulators
amio/format/formats2.cpp

16. format2.cpp
#include <iostream> #include <iomanip> using namespace std; void PrintData(int x, double y) { cout << setw(15) << x; cout << setw(25) << y; cout << setw(30) << “Hello, World” << endl; }

17. format2.cpp
int main() { int a; double b; cout << “Enter an integer: “; cin >> a; cout << “Enter a double: “; cin >> b; cout << endl; PrintData(a, b); cout << fixed << showpoint << left << setprecision(5);

18. format2.cpp
cout << scientific << right << setprecision(1); PrintData(a, b); cout << showpoint << setfill(‘.’); cout << internal; cout << “\nSee ya!\n”; }

19. Example: Integer Output in Decimal, Octal, and Hex
amio/format/bases.cpp

20. bases.cpp
#include <iostream> #include <iomanip> using namespace std; void PrintValues(int x, int y, int x) { cout int WID = 20; … cout << dec << “Decimal “ << setw(WID) << x << setw(WID) << y << setw(WID) << z << endl;

21. bases.cpp
cout << oct << “Decimal “ << setw(WID) << x << setw(WID) << y << setw(WID) << z << endl; cout << hex<< “Decimal “ << setw(WID) << x << setw(WID) << y << setw(WID) << z << endl; }

22. bases.cpp
int main() { int x = , y = , z = ; PrintValues(x, y, z); cout.setf(ios::showbase); cout.setf(ios::uppercase); return 0; }