general questions regarding value and reference semantics

[Ali Çehreli]

On 04/28/2013 05:22 PM, WhatMeWorry wrote:

 > Does a fixed-length, static array behave with value semantics

Yes, a static array has value semantics. When assigned, a variable of a 
static array type will get its own elements, separate from the right 
hand side's elements.

     int[2] a;
     int[2] b = a;  // b and a have separate elements
     int[2] c;
     b = c;         // b's elements are copied from c's

 > while a dynamic array behave with reference semantics?

Yes, because a dynamic array does not own any elements. It is a handle 
to reach those elements.

 > And then what to make of Phobos' std.container, when it says "DList uses
 > neither reference nor value semantics."  Is there some hybrid or new
 > undiscovered semantic I've never heard about?

I don't have experience with DList but looking at its documentation, a 
DList is obviously a reference to a part of something called a chain. In 
that sense, DList has reference semantics.

On the other hand, every DList variable owns the chain as well, because 
they can actually remove elemnents from it regardless of whether others 
are still referring parts of it. (Apparently, it is not undefined 
behavior nor it invalidates other DList variables: The other variables 
simply start seeing a shorter chain of elements.)

Ali