ECE 264 Object-Oriented Software Development

1. ECE 264Object-Oriented Software Development Instructor: Dr. Honggang Wang Fall 2012 Lecture 7: Continuing with output formatting; File I/O

2. Lecture outline • Announcements/reminders • Lab 2 due Mon. 09/24 • Will submit to M:\ECE-264\<username> • Review: output formatting • Changing precision • Forcing decimal point to be displayed • Today • Continue with output formatting • Changing field widths • Changing justification within fields • Changing fill characters • File I/O ECE 264: Lecture 7

3. Review • Output formatting • Change base with dec/oct/hex or setbase() • Change precision (# places after decimal point) with precision() or setprecision() • Be sure to specify fixed format! • Force decimal point to be shown with showpoint ECE 264: Lecture 7

4. Field Width (width, setw) • Field width • (for ostream) Number of character positions in which value is outputted • Fill characters are inserted as padding • Values wider than the field are not truncated • (for istream) Maximum number of characters inputted • For char array, maximum of one fewer characters than the width will be read (to accommodate null character) ECE 264: Lecture 7

5. Field Width (width, setw) (Cont.) • Field width (Cont.) • Member function width of base class ios_base • Sets the field width • Returns the previous width • width function call with no arguments just returns the current setting • Parameterized stream manipulator setw • Sets the field width • Field width settings are not sticky ECE 264: Lecture 7

6. Example 5: width // Fig. 15.10: Fig15_10.cpp: Demonstrating member function width. #include <iostream> using std::cin; using std::cout; using std::endl; int main() { int widthValue = 4; char sentence[ 10 ]; cout << "Enter a sentence:" << endl; // set field width, then display characters based on that width do { cin.width( 5 ); // input only 5 characters from sentence cin >> sentence; cout.width( widthValue++ ); cout << sentence << endl; }while(sentence[0] != ‘.’); // end while return 0; } // end main ECE 264: Lecture 7

7. Example 5 output Enter a sentence: This is a test of the width member function. This is a test of the widt h memb er func tion . ECE 264: Lecture 7

8. Justification (left, right and internal) • Justification in a field • Manipulator left • fields are left-justified • padding characters to the right • Manipulator right • fields are right-justified • padding characters to the left • Manipulator internal • signs or bases on the left • showpos forces the plus sign to print • showbase forces the base to print (for octal/hex) • magnitudes on the right • padding characters in the middle ECE 264: Lecture 7

9. Example 6: right/left justification // Fig. 15.14: Fig15_14.cpp--Demonstrating left justification and right justification. #include <iostream> using std::cout; using std::endl; using std::left; using std::right; #include <iomanip> using std::setw; int main() { int x = 12345; // display x right justified (default) cout << "Default is right justified:" << endl << setw( 10 ) << x; // use left manipulator to display x left justified cout << "\n\nUse std::left to left justify x:\n" << left << setw( 10 ) << x; // use right manipulator to display x right justified cout << "\n\nUse std::right to right justify x:\n" << right << setw( 10 ) << x << endl; return 0; } // end main ECE 264: Lecture 7

10. Example 7: internal justification // Fig. 15.15: Fig15_15.cpp // Printing an integer with internal spacing and plus sign. #include <iostream> using std::cout; using std::endl; using std::internal; using std::showpos; #include <iomanip> using std::setw; int main() { // display value with internal spacing and plus sign cout << internal << showpos << setw( 10 ) << 123 << endl; return 0; }// end main Output: + 123 ECE 264: Lecture 7

11. Padding (fill, setfill) • Padding in a field • Fill characters are used to pad a field • Member function fill • Specifies the fill character • Spaces are used if no value is specified • Returns the prior fill character • Stream manipulator setfill • Specifies the fill character ECE 264: Lecture 7

12. Example 8: setfill, setw // Fig. 15.16: Fig15_16.cpp // Using member-function fill and stream-manipulator setfill to change // the padding character for fields larger than the printed value. #include <iostream> using std::cout; using std::dec; using std::endl; using std::hex; using std::internal; using std::left; using std::right; using std::showbase; #include <iomanip> using std::setfill; using std::setw; ECE 264: Lecture 7

13. Example 8: setfill, setw (cont.) int main() { int x = 10000; // display x cout << x << " printed as int right and left justified\n" << "and as hex with internal justification.\n" << "Using the default pad character (space):" << endl; // display x with base cout << showbase << setw( 10 ) << x << endl; // display x with left justification cout << left << setw( 10 ) << x << endl; // display x as hex with internal justification cout << internal << setw( 10 ) << hex << x << endl << endl; // display x using padded characters (right justification) cout << right; cout.fill('*' ); cout << setw( 10 ) << dec << x << endl; // display x using padded characters (left justification) cout << left << setw( 10 ) << setfill( '%' ) << x << endl; // display x using padded characters (internal justification) cout << internal << setw( 10 ) << setfill( '^' ) << hex << x << endl; return 0; } // end main ECE 264: Lecture 7

14. Example: setfill, setw (output) ECE 264: Lecture 7

15. Final notes • Next time • File I/O • Introduce classes • Acknowledgements: this lecture borrows heavily from lecture slides provided with the following texts: • Deitel & Deitel, C++ How to Program, 8th ed. • Etter & Ingber, Engineering Problem Solving with C++, 2nd ed. ECE 264: Lecture 7