ECE 264 Object-Oriented Software Development Instructor: Dr. Honggang Wang Fall 2012 Lecture 6: Continuing with output formatting

Lecture outline Announcements/reminders  Lab 2 due Mon. 09/24 Will submit to M:\ECE-264\ TA office: SENG am (Tue), 11-12:00 pm (Thur) Attendance ( bonus quiz in class: 3%, required for lab) Review  get(), getline(), and ignore()  Started output formatting—bases Continue with output formatting 10/1/2015 ECE 264: Lecture 6 2

Review Input ( cin ) streams  Use cin to read values into variables E.g., cin >> x; Skips whitespace characters Input value must be compatible with type of x  Reading n characters: cin.get(buffer, n); Reading 1 character: cin.get(ch);  Reading an entire line (at most m characters): cin.getline(buffer, m)  May need cin.ignore(x) to skip characters Output formatting  Change base with dec/oct/hex or setbase() 10/1/2015 ECE 264: Lecture 6 3

Example 2: bases //Example: Determine the output #include using std::cout; using std::endl; using std::hex; using std::oct; int main() { int i; for (i = 0; i <= 32; i += 8) { cout << "Decimal: " << i << endl; cout << oct << "Octal: " << i << endl; if ((i % 16) == 0) cout << hex << "Hexadecimal: " << i << endl; } return 0; } 10/1/2015 ECE 264: Lecture 6 4

Example 2: bases (cont.) Output: Decimal: 0 Octal: 0 Hexadecimal: 0 Decimal: 8 Octal: 10 Decimal: 20 Octal: 20 Hexadecimal: 10 Decimal: 18 Octal: 30 Decimal: 40 Octal: 40 Hexadecimal: 20 10/1/2015 ECE 264: Lecture 6 5 What’s the problem?  Base settings are sticky How would we fix it?  Insert “ dec ” into the cout statement for the decimal values

FP Precision ( precision, setprecision ) Precision of floating-point numbers  Number of digits displayed to the right of the decimal point  setprecision parameterized stream manipulator  precision member function When called with no arguments, returns the current precision setting  Should always use with fixed format  Precision settings are sticky 10/1/2015 ECE 264: Lecture 6 6

Example 3: setprecision // Fig. 15.9: Fig15_09.cpp // Controlling precision of floating-point values. #include using std::cout; using std::endl; using std::fixed; #include using std::setprecision; #include using std::sqrt; // sqrt prototype 10/1/2015 ECE 264: Lecture 6 7

Example 3: setprecision (cont.) int main() { double root2 = sqrt( 2.0 ); // calculate square root of 2 int places; // precision, vary from 0-9 cout << "Square root of 2 with precisions 0-9." << endl << "Precision set by ios_base member function " << "precision:" << endl; cout << fixed; // use fixed point format // display square root using ios_base function precision for ( places = 0; places <= 9; places++ ) { cout.precision( places ); cout << root2 << endl; } // end for cout << "\nPrecision set by stream manipulator " << "setprecision:" << endl; // set precision for each digit, then display square root for ( places = 0; places <= 9; places++ ) cout << setprecision( places ) << root2 << endl; return 0; } // end main 10/1/2015 ECE 264: Lecture 6 8

Example 3 output 10/1/2015 ECE 264: Lecture 6 9

Trailing Zeros and Decimal Points ( showpoint ) Stream manipulator showpoint  Floating-point numbers are output with decimal point and trailing zeros Example  79.0 prints as instead of 79  Reset showpoint setting with noshowpoint  Implies a default precision of 6 Can override with precision / setprecision 10/1/2015 ECE 264: Lecture 6 10

Example 4: showpoint, setprecision #include using std::cin; using std::cout; using std::endl; using std::fixed; using std::showpoint; #include using std::setprecision; int main() { double i, j, x, y; cin >> i >> j >> x >> y; cout << fixed << showpoint; cout << "First output " << endl; cout << i << ',' << j << ',' << setprecision(3) << x << ',' << y << endl; return 0; } // Input stream is: /1/2015 ECE 264: Lecture 6 11 First output , ,3.400,5.000 _

Final notes Next time Finish formatted output—field widths, justification, and fill characters Acknowledgements: this lecture borrows heavily from lecture slides provided with the following texts: Deitel & Deitel, C++ How to Program, 8 th ed. Etter & Ingber, Engineering Problem Solving with C++, 2 nd ed. 10/1/2015 ECE 264: Lecture 6 12