Functions

• Void Functions

  • void function_name() {
       body
    }
           

  • example:

  • void Greeting() {
       cout << "Welcome to my program" << endl;
       cout << "   Please enjoy your stay " << endl;
    }
    
    int main () {
        Greeting();
        Greeting();
    }
           

  • Flow of control
  • Write a function that presents a question and four menu choices.

• User Defined functions
  • Flow of control
  • Parameters
    • A method of passing information to and from a function
  • Function prototype
    • Defininig the type and formal parameters of a function
  • Function call
    • Transfering control to, and passing arguments to a function
  • Function declaration
    • Defining the function
    • Defining local variables, or variables available only to the function.
    • Includes a return statement, which returns a variable of the type of the function

• Parameter
  • A value parameter (or constant parameter) passes only the value to the function
  • A reference parameter (or variable parameter) is a parameter that can be changed.
  • Parameters in the agrument list (call) must match the formal parameter list in type, variablilty and number.
  • They are passed according to position.

• Designing Functions
  • Interface - a connecting link at a shared boundry that permits independant systems to meet and act or communicate with each other.
  • Encapsulation - Hiding a module implementation in a separate block with a formally specified interface.
  • Often pre and postconditions are written as part of the function's documentation.

• Examples Parameter
  • prototype

  • void name (type name, type name, type name, ...);
    	

  • call

  • name(arg1, arg2, arg3, ...)
    	

  • declaration

    void name (type name, type name, type name, ...) {
         local variable declarations
    
         statements
    
         return
    }
        

• Functions should have a single point of exit. (one return per function)

• Write a yes/no question asker.
• Write a program to implement a four choice menu with response output
• Write a midpoint rule root finder.