The University of Iowa
The College of Liberal Arts and Sciences
Department of Computer Science

Programming Languages and Tools:

CS:3210:0001

Lecture/Lab #11

Programming with C++

Operator overloading (part II), enums, member access control

Warm up

  • Is the following a valid C++ program? If so, what does it do?

int main() {
    int n = 42;
    int& r;
    r = n;
    std::cout << r << std::endl;
}

  • How about this one?

auto square( int n ) { return n * n; }

int main() {
    int& i = 17;
    std::cout << i << std::endl;

    int& j = square( 2 );
    std::cout << j << std::endl;
}

Operator overloading (part II)

  • Operators =, [], (), and -> are required to be defined as member functions

https://repl.it/@agurtovoy/lab11-overloading

  • Operators +=, -=, ++, --, *=, /=, unary +, unary - are commonly defined as member functions
  • Operators +, -, *, /, <, >, <=, >=, ==, !=, >>, << are commonly defined as freestanding functions
  • The first parameter of an output operator << is a reference to a nonconst std::ostream object
  • The first parameter of an input operator >> is a reference to a nonconst std::istream object

Exercise 1

Define a stream output operator for type `rectangle`

https://repl.it/@agurtovoy/lab11-exercise1

  • Open the exercise template

  • Write your code, press Run to test

  • When you're done, grab your Repl's link and send it as a direct message to me (agurtovoy)

  • Click on the corresponding option in the "Lab11 exercises" poll in #general

User-defined types: enum

https://repl.it/@agurtovoy/lab11-enum

  • Enumerations let us group together sets of integral constants.
  • In scoped enumerations the constants are scoped within the enumeration type.
  • In unscoped enumerations the constants are placed into the same scope as the enumeration itself.
  • By default, constant values  (aka enumerators) start at 0 and each next constant has a value 1 greater than the preceding one. 
  • But we can supply explicit initializers to any or all of the enumerators.
  • Objects/constants of an unscoped enumeration type are implicitly converted to an integral type.

Exercise 2

Define a stream output operator for an enumeration type

https://repl.it/@agurtovoy/lab11-exercise2

  • Open the exercise template

  • Write your code, press Run to test

  • When you're done, grab your Repl's link and send it as a direct message to me (agurtovoy)

  • Click on the corresponding option in the "Lab11 exercises" poll in #general

Member access control

https://repl.it/@agurtovoy/lab11-access-control

  • Public members define the interface of the type and are accessible to all parts of the program.
  • Private members are considered to be implementation details and are accessible to the member functions of the type only.
  • A class may contain zero or more access specifiers, and there are no restrictions on how often an access specifier may appear. 
  • Each access specifier specifies the access level of the succeeding members. 
  • The specified access level remains in effect until the next access specifier or the end of the class body.
  • The only difference between class and struct keywords is the default access level.
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