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From: niklas@appli.se (Niklas Hallqvist)
Newsgroups: comp.lang.c++
Subject: Re: MEMBER ACCESS
Message-ID: <1390@appli.se>
Date: 3 Jun 91 10:17:16 GMT
References: <97edfa6b92f028446f60@rose.uucp>
Organization: Applitron Datasystem AB, GOTHENBURG, SWEDEN
Lines: 51

phil.calvin@rose.uucp (PHIL CALVIN) writes:


> A language feature I'd like to see...
There is language support for this already...

> A class has certain data members, for efficiency reasons, I would like
>to grant the USER read-only access.

> EX:

> class COORD
>   {
> public:
>   // Don't modify just read..
>   int x,y;
>   ...
>   };

> Obviously, the comment does little more than _encourage_ the user to
>modify the value.  My proposal is to have language support for this
>concept:

class COORD {
  int _x;
  int _y;
public:
  const int& x;
  const int& y;

  COORD() : x(_x), y(_y) {}
};

int main(int, char**)
{
  COORD p;
  int X = p.x;
  int Y = p.y;
//  p.x = X;		// ERROR!
//  p.y = Y;		// ERROR!
}

As you can see, no new language constructs are needed.

						Niklas

-- 
Niklas Hallqvist	Phone: +46-(0)31-40 75 00
Applitron Datasystem	Fax:   +46-(0)31-83 39 50
Molndalsvagen 95	Email: niklas@appli.se
S-412 63  GOTEBORG, Sweden     mcsun!sunic!chalmers!appli!niklas