Re: Question about function template(from Thinking in C++ book)

From:

"Igor Tandetnik" <itandetnik@mvps.org>

Newsgroups:

microsoft.public.vc.language

Date:

Sun, 19 Jul 2009 00:32:01 -0400

Message-ID:

<eA6KgnCCKHA.4792@TK2MSFTNGP05.phx.gbl>

chrisben wrote:

Here are sample codes from Thinking in C++ Vol I, page 776

// A function template:
template<class Iter>
void drawAll(Iter start, Iter end) {
while(start != end) {
(*start)->draw();
start++;
}
}

What I do not understand is line
(*start)->draw();

If Iter is a pointer, should that be start->draw(), instead of
(*start)?

Obviously, Iter is intended to be analogous to a double pointer - a
pointer into a collection of pointers to objects (perhaps smart
pointers). Something along the lines of:

class Shape {
public:
  virtual void draw() = 0;
};

class Circle : public Shape {
public:
  void draw();
};

class Square : public Shape {
public:
  void draw();
};

vector<Shape*> shapes;
shapes.push_back(new Circle);
shapes.push_back(new Square);

drawAll(shapes.begin(), shapes.end());

--
With best wishes,
    Igor Tandetnik

With sufficient thrust, pigs fly just fine. However, this is not
necessarily a good idea. It is hard to be sure where they are going to
land, and it could be dangerous sitting under them as they fly
overhead. -- RFC 1925