OOP Class Lawrence D

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OOP ClassLawrence DAntonio

• Lecture 1

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Quiz 1

• (1) What Danish computer scientist invented C?
• Bjarne Stroustrup
• (2) What was the first object-oriented
  programming language?
• Simula

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• (3) What does STL stand for and who invented it?
• Standard Template Library, Alex Stepanov
• (4) (a) Which language is older C or Java?
• C (sort of)
• (b) Which language is older C or Smalltalk?
• Smalltalk

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• (5) True or false C was designed to be
  backwards compatible with C.
• True (a least in theory, in practice is another
  story)
• (6) What is the difference between overloading
  and polymorphism?
• Overloading creates many functions of the same
  name that work on different types. Polymorphism
  creates one function that work on different
  types.

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• (7) True or false Only object-oriented
  programming languages can exhibit polymorphism.
• False, many languages exhibit polymorphism. In
  Lisp, car and cons are examples of polymorphic
  functions.

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• (8) What is the difference between function
  overloading and function overriding?
• Overloading involves functions of the same name
  having different signatures. Overriding occurs in
  when a function in a derived class replaces a
  function of the same name in the base class.

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• (9) What is a function object?
• A function object is an object that may be called
  like a function. In C this is achieved by
  overloading the () operator.
• (10) How does a function object differ from a
  function?
• A function object has state. It can be
  initialized through a constructor and retains its
  state between invocations.

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• (11) Which of the following C mechanisms is
  used to create polymorphism?
• Virtual functions X Templates X
• Virtual functions exemplify inclusion
  polymorphism. A reference or pointer to a parent
  object may be converted to an object of any
  inherited type. This means that determining which
  method is being called is a run-time decision.
• Templates implement the concept of parametric
  polymorphism. Code works correctly for a variety
  of datatypes. Functional languages such as ML,
  Haskell, Lisp typically use parametric
  polymorphism.

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• (12) What is a predicate in C?
• A function or function object that returns a
  boolean.
• (13) What is the primary difference between a
  struct and a class in C?
• In a struct, access is public by default whereas
  in a class it is private by default.

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• (14) What is the meaning of the key word mutable?
• A data member of a class is declared to be
  mutable then it may be modified inside a const
  member function.

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Mutable example
Ex class Image private mutable bool
is_loaded public void Redraw() const if
(is_loaded false) //load image from
disk is_loaded true //..paint image on
screen
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• (15) What are the member functions that the
  compiler will write for you?
• Default constructor, copy constructor, assignment
  operator, destructor
• (16) True or false a default constructor cannot
  take any arguments
• False. A default constructor must either have no
  arguments or all arguments must have default
  values

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• (17) What are the four cast operators in C?
• static_cast, dynamic_cast, reinterpret_cast,
  const_cast

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• (18) Which of the following conversions is
  generally not legal?
• (a) Converting a base object to a derived object?
• Not legal (the base object is not a derived
  object).
• (b) Converting a derived object to a base object?
• Legal (the derived object is a base object).

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• (19) What is an exception specification?
• A specification of what types of exceptions a
  function may throw (or none at all).

void f() throw(int) //throws only an int void
g() throw() //throws no exceptions
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• (20) What is a nothrow function and how do you
  declare it?
• A nothrow function guarantees that it wont
  throw an exception. The only example currently
  allowed is the nothrow new operator.

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nothrow code
Class X // X p new (nothrow) X Note
even though this code wont throw an exception,
one can still check if the allocation was
successful by using the code if (!p) //
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• (21) True or false it is illegal for a
  destructor to throw an exception.
• False, but it is generally a bad idea.

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• (22) How do you declare and allocate memory for a
  two dimensional array A with n rows and m columns
  (where n,m are integer variables determined at
  run-time)?

int A A new intn for(int i 0 i lt n
i) Ai new intm
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• (23) What is the most significant difference
  between malloc() (the C dynamic memory allocation
  function) and new() (the C dynamic memory
  allocation operator)?
• malloc() doesnt call a constructor for allocated
  objects, while new() does.

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• (24) (a) Is the following code legal?

class X class Y public X main() X p
new Y Legal, since a Y is an X.
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• (b) Is the following code legal?

class X class Y private X main() X
p new Y Illegal, since private inheritance
is used, Y is not an X.
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• (25) What is a smart pointer?
• A smart pointer is an object that acts like a
  pointer. A smart pointer can have state, so it
  can be responsible for owning what it points to.
  auto_ptr is an example of a smart pointer in the
  standard library.

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• (26) What is wrong with this code?

int p new int10 //do stuff with p delete
p In order to delete an array, one must use the
syntax delete p
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• (27) What is wrong with this code?

class X private int a public X(int n) a(n)
main() X p new X new X calls the
default constructor for X, but the class does not
have any default constructor defined.
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• (28) (a) What is wrong with the following
  declaration?

class X public int x X(int a) x(a) void
f(int a) const main() X my_x(5) int p
my_xx p 8 return 0 p is an int
pointer, but Xx is an int inside class X. One
needs to declare and use p like this int Xp
Xx my_x.p 8
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• (30) What is wrong with the following function?

int foo(const vectorltintgt v) n
v.size() if (n 0) //Check if vector is
empty cout ltlt Error Empty vector\n return
-1 return v0 n 0 should be n 0
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• (31) True or false the following code is legal.

include ltiostream.hgt include ltiostreamgt main()
cout ltlt Hello World return 0 True, it
is legal. The cout called is the one in iostream.h
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• (32) What is wrong with the following code?

string operator.(const string s, const string
t) string temp(s) temp.append(t) return
t It is wrong because a reference to a local
variable is returned. But that local object
passes out of scope when the function is
completed.
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• (33) For each of the following state whether the
  code is legal or illegal and say why.

• int f1(int x)
• main()
• f1(5) 6
• Illegal, since f1 returns a temp value (hence no
  lvalue).

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(b) int f2(int x) main() f2(5) 6
Legal, since f2 returns an lvalue.
(c) const_int f3(int x) main() f3(5)
6 Illegal, since f3 returns a const (no
lvalue).
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• (34) Whats wrong with the following code?

template ltclass Containergt void fun(const
Container x) Containeriterator i for(i
x.begin() i ! x.end() i) cout ltlt
i The compiler wont know what kind of
object Containeriterator is. Instead, one must
use typename Containeriterator i
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• (35) You have a string s. Write one line of C
  code that prints (to standard output) the string
  in reverse order.

reverse_copy(s.begin(), s.end(),
ostream_iteratorltchargt(cout))