Is this a bug?

import std.stdio;

class C
{
	int[] x;
}

void main()
{
	C[] arr;
	arr.length = 3;
	arr[] = new C; /* this is the offending line, it doesn't happen if I */
			/*initalize each independently */

	foreach (ref c; arr)
	{
		c.x ~= 5;
		writefln(c.x);
	}
}

the printed result is:
[5]
[5,5]
[5,5,5]

I expected it to be:
[5]
[5]
[5]

I didn't find any explanation for this kind of behaviour in the docs, and it does seem like a bug to me.

D 1.027 by the way.

"Denton Cockburn" <diboss@hotmail.com> wrote in message news:pan.2008.03.04.13.32.00.785638@hotmail.com...

> arr[] = new C; /* this is the offending line, it doesn't happen if I */

This creates *one* instance of C and sets all the elements of arr to point to that single instance.

Hence:

> [5]
> [5,5]
> [5,5,5]

You keep modifying the same array.  :)

On Tue, 04 Mar 2008 08:53:35 -0500, Jarrett Billingsley wrote:

> "Denton Cockburn" <diboss@hotmail.com> wrote in message news:pan.2008.03.04.13.32.00.785638@hotmail.com...
> 
>> arr[] = new C; /* this is the offending line, it doesn't happen if I */
> 
> This creates *one* instance of C and sets all the elements of arr to point to that single instance.
> 
> Hence:
> 
>> [5]
>> [5,5]
>> [5,5,5]
> 
> You keep modifying the same array.  :)

Yeah, would be nice if that was mentioned somewhere.

in the section of the docs where:
s[] = 3;		// same as s[0] = 3, s[1] = 3, s[2] = 3

I (naively) expected:

s[] = new C;  // to be same as s[0] = new C, s[1] = new C, s[2] = new C
or
s[] = foo(); // where foo returns an object (a different one each time)

easy to work with and around as is, but would be rather nice to be able to do what I just stated.  Syntactic sugar for 2.0?

Denton Cockburn:
> easy to work with and around as is, but would be rather nice to be able to do what I just stated.  Syntactic sugar for 2.0?

I think the current behavior is better, despite being a little less intuitive, because it's more uniform: it copies the value to all the cells. In such situation the value is the object reference, that is many references to the same object. So I think that sugar you talk about is bad for your health in the long run.

Bye,
bearophile