pointers, assignments, Garbage Collection Oh My?

[JohnnyK]

On Wednesday, 10 July 2013 at 18:45:56 UTC, H. S. Teoh wrote:
> On Wed, Jul 10, 2013 at 08:38:40PM +0200, JohnnyK wrote:
> [...]
>> Reminds me of how Delphi (aka Pascal) strings are work.  Thanks
>> everyone this answers some of my questions.  Now what about 
>> when the
>> return type of a function is a string?  Is D returning the 
>> pointer
>> to the string structure or is it returning the structure?
>
> D structs are always passed by value, so it's the 
> length+pointer pair
> that's being returned. There's no extra indirection involved 
> here. What
> it points to stays where it is on the GC heap.
>
> So for example:
>
> 	int[] data = [1,2,3];
>
> 	int[] f() {
> 		return data;
> 	}
>
> 	void main() {
> 		auto arr = f();	// returns copy of data's ptr+length
> 		arr.length--;	// modifies this copy
> 		assert(arr == [1,2]);
> 		assert(data == [1,2,3]); // data itself hasn't changed
> 	}
>
> Does this help?
>
>
I understand thanks for the information.