?
Solved

can someone please tell me what this does?

Posted on 2002-03-27
4
Medium Priority
?
216 Views
Last Modified: 2010-04-02
I'm taking a beginner's C++ class, and long story, but for now I have to work without the textbook.

This is from a class point (for a triangle) example.

I have a basic understanding of classes, but what I can't find any help on is this:

double distance (const point& another) const;

My questions: what does the ampersand at the end of point& do, and is "another" a keyword, or is it an arbitrary assignment, and what does it do?

Thank You Thank You, for your time.
0
Comment
Question by:celere
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
4 Comments
 
LVL 30

Expert Comment

by:Axter
ID: 6901830
The ampersand means the variable takes a reference, and "another" is a type, not a keyword.
0
 
LVL 16

Accepted Solution

by:
Peter Kwan earned 200 total points
ID: 6901833
& means "reference" in C++. As in your example, the code says that you pass the argument into the function as reference, which means that the argument you passed into the function can be changed and the change inside the function is reflected outside the function.

Let me give another example to illustrate and help you to understand:

void fn(int& x) {
   x=1;
}

void fn1(int x) {
   x=4;
}

int main() {
  int x=9;
  cout << "Before: " << x << endl;
  fn(x);
  cout << "After fn: " << x << endl;
  fn1(x);
  cout << "After fn1: " << x << endl;
  return 0;
}

In this example, the output is:
Before: 9
After fn: 1
After fn1: 1

=========================================================
"another" is not a keyword, it is just a name of the argument. You can replace it with any valid name you like (of course you need to change the name of all the instances with the name "another" inside that function as well).
0
 
LVL 3

Expert Comment

by:MDarling
ID: 6902029
Another is not a type or a keyword, it is a variable of type "point".

I'm guessing that

double distance (const point& another) const;

is supposed to be a member function of the class point.  If so then good old Pythagoras would help you determine the distance from point to point.

class point
{
double x,y;
public:
point(double _x,double _y);
double distance(const point& another) const
{
   double d=...;
   // pythagoras
}
};

Regards,
Mike.
0
 
LVL 3

Expert Comment

by:MDarling
ID: 6902031
Correction: Another is not a type or a keyword, it is a reference to a variable of type "point".
0

Featured Post

Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

C++ Properties One feature missing from standard C++ that you will find in many other Object Oriented Programming languages is something called a Property (http://www.experts-exchange.com/Programming/Languages/CPP/A_3912-Object-Properties-in-C.ht…
Go is an acronym of golang, is a programming language developed Google in 2007. Go is a new language that is mostly in the C family, with significant input from Pascal/Modula/Oberon family. Hence Go arisen as low-level language with fast compilation…
The goal of the video will be to teach the user the concept of local variables and scope. An example of a locally defined variable will be given as well as an explanation of what scope is in C++. The local variable and concept of scope will be relat…
The viewer will be introduced to the technique of using vectors in C++. The video will cover how to define a vector, store values in the vector and retrieve data from the values stored in the vector.
Suggested Courses

777 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question