T[new] misgivings

[Max Samukha]

On Fri, 16 Oct 2009 02:53:20 -0700, Walter Bright
<newshound1 at digitalmars.com> wrote:

>Don wrote:
>> Max Samukha wrote:
>>> // arrays are true reference types
>>> int[new] a = [1, 2, 3];
>>> b = a;
>>> a.length = 22;
>>> assert (a.length == b.length);
>> 
>> This makes perfect sense to me. The rule would be:
>> If 'x' is T[new], then:
>> x = y; _always_ copies y into a {length, capacity-specified block}, 
>> unless it already is one. x is given a pointer to the start of that block.
>> x[] = y[]; does a memcpy, regardless of whether y is a T[new] or a T[].
>
>Right. Assignment of a reference type does not copy the values of what 
>is referred to. Only the reference is copied.
>
>I think it would be very strange to have T[] behave like a reference 
>type (which it does now) and T[new] to behave like a value type.

By "true reference type", I meant:

struct ArrayRef
{
    Array* ptr;
}

struct Array
{
   void* data;
   size_t length;
   // size_t capacity;
}

The fat reference approach for arrays has sucked from day one (IMHO).

I think performance-critical code will use slices (read - ranges)
anyway, so the additional allocation and indirection is not a big
issue.