CIS 101: Computer Programming and Problem Solving Lecture11 Usman Roshan Department of Computer Science NJIT

Classes Let’s say we want to define a rectangle object. This is the same defining a new type of variable called rectangle. Previous types we have seen so far are int, char, float, and their pointers. int length; int width; int area(); float diagonal(); This is our rectangle class. it contains the length and width, and also functions to compute the area and diagonal. Rectangle

Defining classes class { public: ; … private: … };

Rectangle class

Constructors, destructors, and copy constructor Constructor: get called when a new instance of the object is created. –rectangle myrec; //constructor gets called Destructor: gets called when you exit the scope of the variable –void myfunction(){ rectangle myrec; myrec.setlength(2); myrec.setwidth(1); myrec.print(); –} //once we exit this function the destructor gets called Copy constructor: gets called everytime a copy of the object is created –rectangle myrec2 = myrec;//not called in this case, we’ll have to write a //separate function for this which (if time) we may see later –void myfunction(rectangle myrec); –void main(){ rectangle myrec; myfunction(myrec) //at this point a copy of myrec is created that is local to //myfunction –}–}

Constructor Everytime we create a rectangle its length and width are automatically set to 2 and 2.

Overloading constructor You can have two or more constructors: convert and default Also called function overloading

Copy constructor Implicit copy constructor is called which copies width and length of r1 into width and length of r2.

String class

Strings mystring p size7 string(int s){ size = s; p = new char[size]; } string mystring(7); string( string& from) { size = from.size; p = from.p; } string mystring2(mystring); mystring2 p size7

Strings mystring p size7 string(int s){ size = s; p = new char[size]; } string mystring(7); string( string& from) { size = from.size; p = new char[size]; for(int i=0;i<size;i++){ p[i]=from.p[i]; } string mystring2(mystring); mystring2 p size7

Lab problems 1.Create string class and add functions: 1.Copy string 2.Compare string for equality 3.Concatenate strings 4.Substring 2.Create Vector class 1.Copy vector 2.Vector equality 3.Dot product 4.Euclidean norm (length) of vector