Functions and Output

• Functions
  • C,C++ have a large libraries of functions
  • These are "mini" programs that do something
  • They always return a value to the calling routine
  • They usually require parameters from the calling routine

  • float x;
    float angle;
    ...
    x = cos(angle);
    	

  • In this example, we calculate the cosine of angle and store it in x.
  • We call the cos function
  • Our routine is the calling
  • angle is a parameter
  • it returns a floating point value
  • There is a table of functions on page 113
    • Generaly, they all require a header file to be included
    • They all take parameters
    • There are many many more.
  • Some functions don't return a value, and they are called void functions.
  • We will deal with this much more in chapters 7 and 8.
  • Write a program that will calculate the volume of a sphere given it's radius. (V = 3/4*PI*r³)
• Formating Output

  • int a,b,c;
    
    a = 5;
    b = 7;
    c = 4;
    cout << a << b << c << endl;
    

  • What results would you get from this
  • cout << a << " " << b << " " << c << endl;
  • What if we wanted to make a table where everything was right justified?

  • int a,b,c;
    
    a = 15;
    b = 127;
    c = 34;
    cout << a << endl;
    cout << b << endl
    cout << c << endl;
    

  • setw(n)
    • #include <iomanip>
    • only for numbers and strings
    • use (at least) n characters for output
    • cout << setw(4) << 3 << endl;
    • only works for the next insertion into the output stream
  • setprecision(n)
    • for the life of the of the program (or until another is called)
    • the number of digits to the right of the decimal point
  • showpoint
    • shows the decimal point
    • Broken on our system
    • cout.setf(ios::showpoint);
  • fixed
    • shows floats in normal notation, not scientific
    • Broken on our system
    • cout.setf(ios::fixed, ios::floatfield);