CS 455 Lecture Notes

Week Four, Thursday: Functions

Use existing library functions when possible.

Math Library Functions

These include logarithm, exponential, and power functions; trigonometric functions; and floating point and integer operation functions (floor, ceiling, and absolute value).

Declarations (Function Prototypes) and Definitions

Always use function prototypes (although they are not required by the compiler if they are defined before they are called). In large programs, function prototypes should be declared in a header (*.h) file.

Pseudo-Random Number Generation

Create a random integer over a defined range:

  rand() % 6

for example.

Scope Issues

Never use global variables. Global constants are OK.

Keyword static example:

void f1()
{
  static int count = 1;        // Initialized only the first time f1() is called.
  int i = 1;                   // Initialized every time f1() is called.

  count++;
}                              // i goes "out of scope" but count does not.

Recursion

Example: Fibonacci numbers.

Function Overloading

Different functions can have the same name if their parameter lists are different.

Function Templates

Another way to get the effect of function overloading is with function templates.

This page established September 19, 1999; last updated September 19, 1999.