Strange Initialize..........

milestanley

In "Programming Priciples and Practice Using C++". chapter 17.5 destructors

//a very simplified vector of doubles
class vector{
int sz; // the size
double* elem; //a pointer to the elements
public:
vector(int s) //constructor
:sz(s), //"initialize sz", I have no idea what does it mean that writting?
elem(new double[s]) //initialize elem, and the same as above
{
for(int i=0; i < s;i++) elem[i]=0; //initialize elements
}
int size() const {return sz;} //the current size
};

Chris Losinger

//"initialize sz", I have no idea what does it mean that writting? it means "call sz's constructor with the value in s." it's just another way to initialize member variables.

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Lost User

forPower wrote:

  vector(int s)       //constructor
  :sz(s),           //"initialize sz", I have no idea what does it mean that writting?
  elem(new double\[s\])       //initialize elem, and the same as above

It means set the variable sz to the value of the constructor parameter s, and set the variable elem to point to a new array of doubles, of length s. It is a shorthand alternative to writing the lines

sz = s;
elem = new double[s];

_Superman_

A value can be put in a variable by either initialization and assignment. Here is the difference -

// Initializing a variable with a value.
double d = 25.4;

// Assigning a value to a variable.
double d;
d = 25.4;

What you're doing is initializing a class member variable because you cannot do the initialization as I did above inside a class. (You can if the variable is a static const variable.) Read about it here - Initializing C++ Class Members[^]

«_Superman_» I love work. It gives me something to do between weekends.
Microsoft MVP (Visual C++)