Weed wrote:
bearophile пишет:
> Weed:
>> Planned in the future to implement inheritance of structs or the
static creation of classes?
>
> Inheritance of structs: I think it's not planned. Structs in D are
meant to be used for different things than classes.
> Yet, as time passes structs are gaining more power: you can't believe
>
that very recently they have gained constructors/destructors too in D2.
Probably in a system language conceptual purity isn't much appreciated :-)
>
I believe that the opportunity to place an object in memory, stack or
heap is more important than the struggle against "splicing".
I think not worth taking structs and classes from C#. May be bytecode
interpreter C# does not show the difference in speed between the
allocation of memory by a small object + its using and the use of a
static object, so developers C# decided to do so as done. (but I am not
a specialist in the design of compilers :))
> Static creation of classes (I think you mean creation of objects): it
> sounds like an interesting thing, I know of a system language that
> allows the creation of objects only at compile-time, and at
> compile-time it also performs several space optimizations among such
> objects (and such space optimizations often improve running speed a
> little).
And in fact we come to making structs and classes similar except that
classes can not be assigned by value.
Such an option I like.
If I understand you correctly - I think you confuse here two separate
and orthogonal issues.
1) struct vs. class
2) memory allocation
What D tries to do is to provide types with value semantics via structs
and types with reference semantics _and_polymorphism_ via classes.
IMO C++ is a prime example how to not design a language and the slicing
problem is a good example of that. value types should not have
polymorphism whatsoever as is done in D.
memory allocation is orthogonal to this:
class C {...}
Struct S {...}
auto c1 = new C; // classes default to heap alloc
scope c2 = new C; // c2 is on stack
S s1; // structs default to stack
auto s2 = new S; // s2 is S* (heap alloc)
I think Andrei said he wants to make changes to "scope", that is IIRC.
struct inheritance, if it gets implemented in D, should express IMO
semantics similar to concepts as in C++0x, not provide polymorphism for
value types which is clearly a mistake. (also this will remove the need
for typedefs, isn't it?)
