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 | Posted by Derek Parnell
in reply to John Love-Jensen |  Permalink Reply |
|
Derek Parnell 
Posted in reply to John Love-Jensen
| On Sun, 21 Aug 2005 14:29:43 -0500, John Love-Jensen wrote:
> Hi everyone,
>
> I'm new to D Programming Language.
>
> I was wondering how one would code the following (see below) C++ code in D.
>
> Some of the paradigms in particular:
> + using the assignment operator as the setter
> + using the cast operator as the getter
> + working with the output system to print the object's state
>
> This part in D is easy...
> typedef int X;
> typedef int Y;
> ...I wish C++ had actually typing typedef instead of mere aliasing typedef.
>
> The assignment-setter paradigm and the cast-getter paradigm are less clear to me for how to do them in D.
>
> I have no clue how to incorporate Point with import std.stdio's writef.
>
> Thanks,
> --Eljay
>
> - - - - - - - - - - - - - - - - - - -
>
> #include <iostream>
>
> using std::cout;
> using std::endl;
> using std::ostream;
>
> class X
> {
> int m;
> public:
> explicit X(int in) : m(in) { }
> X() : m(0) { }
> operator int () const { return m; }
> };
>
> class Y
> {
> int m;
> public:
> Y() : m(0) { }
> explicit Y(int in) : m(in) { }
> operator int () const { return m; }
> };
>
> class Point
> {
> X x;
> Y y;
> public:
> Point(X inX, Y inY) : x(inX), y(inY) { }
> Point() { }
> void operator = (X inX) { x = inX; }
> void operator = (Y inY) { y = inY; }
> operator X () const { return x; }
> operator Y () const { return y; }
> };
>
> ostream& operator << (ostream& output, Point const& point)
> {
> output << X(point) << "," << Y(point);
> return output;
> }
>
> int main()
> {
> Point point;
> X x;
> Y y;
> x = X(17);
> cout << "point: " << point << "\nx : " << x << "\ny : " << y
> << endl;
> point = x;
> point = Y(33);
> y = point;
> cout << "point: " << point << "\nx : " << x << "\ny : " << y
> << endl;
> }
I'm not really a C++ coder so I had to make a few guesses as to what you expected as the output. Anyhow, here is an attempt to code this in D ...
//--------------------------
import std.stdio;
class X
{
private{
int m;
}
// Constructors
this(int in_val) { m = in_val;}
this() { m = 0; }
// Convert this object into a string form.
char[] toString() { return std.string.format("%d", m); }
}
class Y
{
private{
int m;
}
// Constructors
this(int in_val) { m = in_val;}
this() { m = 0; }
// Convert this object into a string form.
char[] toString() { return std.string.format("%d", m); }
}
class Point
{
private{
X _x;
Y _y;
}
// Constructors
this(X inX, Y inY){ _x = inX; _y = inY; }
this() { _x = new X; _y = new Y;}
// Define some properties...
void x(X inX) { _x = inX; } // setter
X x() { return _x; } // getter
void y(Y inY) { _y = inY; } // setter
Y y() { return _y; } // getter
// Convert this object into a string form.
char[] toString() { return _x.toString ~ "," ~ _y.toString; }
}
int main()
{
Point point = new Point;
X x = new X;
Y y = new Y;
x = new X(17);
writefln("point: " , point.toString, "\nx : " , x.toString ,
"\ny : " , y.toString);
point.x = x;
point.y = new Y(33);
y = point.y;
writefln("point: " , point.toString, "\nx : " , x.toString ,
"\ny : " , y.toString);
return 0;
}
//--------------------------
This program produces the output ...
point: 0,0
x : 17
y : 0
point: 17,33
x : 17
y : 33
--------------------
The main differences are that you need to explicitly do a 'new' for objects otherwise they are not created. There is no way to override the '=' operator in D, but there are 'properties' which replace a lot of uses for '=' overriding. And 'ostream' stuff is generally handled by the toString member function, though theoretically you could override the '<<' operator but that is not the D way.
--
Derek
(skype: derek.j.parnell)
Melbourne, Australia
22/08/2005 10:01:47 AM
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