CS 340 - 2/14/13

Assignment vs. Initialization

   The assignment operator typically executes a
     superset of code from  the initialization code
     (i.e. the copy constructor)


Generics in Java or Templating in C++

template <class X>
X getMax (X a, X b)
{
 if (a < b)
   return b;
 else
   return a;
}


template <class X>
X getMax (X a[], int size)
{
 X temp = a[0];

 for (int i = 1 ; i < size; ++i)
   {
     if (temp < a[i] )
       temp = a[i];
   }

 return temp;
}

//   operator[]
//   myString str1;
//    cout << str1[3];

char MyString::operator[] (int index) const
{
  if (index >= 0 && index < length_)
     return str_[index];
  else
    {
      cerr << "Error: subscript out of range: " 
           << index << endl;
      return '\0';
    } 
}

//   str1[0] = 'J';
char& MyString::operator[] (int index)
{
  if (index >= 0 && index < length_)
     return str_[index];
  else
    {
      cerr << "Error: subscript out of range: " 
           << index << endl;
      return str_[0];   // exceptions are almost needed
    }

}

//    str1 = "Hello";
//    str1[2] = '\0';
//  Warning the above allows the object to enter
//   an invalid data state based on the definition
//   of the object based on the Object Oriented 
//   development

//  Concatenation operator+  (not append!!)

//    str1 = str2 + str3;


// attempt #1  - works but has an extra allocation
//       and deallocation
MyString MyString::operator+ (const MyString& rhs) const
{
   MyString temp;
 
   temp.length_ = strlen (str_) + strlen(rhs.str_);
   delete [] temp.str_;
   temp.str_ = new char[temp.length_ + 1];
   strcpy (temp.str_, str_);
   strcat (temp.str_, rhs.str_ );

   return temp;
}

// attempt #2
MyString MyString::operator+ (const MyString& rhs) const
{
   int tlength = strlen (str_) + strlen(rhs.str_);
   MyString temp(tlength);
 
   strcpy (temp.str_, str_);
   strcat (temp.str_, rhs.str_ );

   return temp;
}


// The above code replies on the following constructor
//   this constructor was defined as PRIVATE since
//   it leaves the object in an invalid state that
//   must be resolved immediately after the call.
MyString::MyString (int len)
  :  str_ (new char [len + 1]),
     length_ (len)
{
}