Classes or stucts :: Newbie

[Andrej Mitrovic]

There's also scoped() in std.typecons, but I think this will still
allocate on the heap. Not sure..

On 12/19/10, bearophile <bearophileHUGS at lycos.com> wrote:
> David Currie:
>
>> I am new to D (like many have done C++ , Java ).
>
> Welcome to D :-)
> What language do you refer to, D1 or D2? The answers here are about the
> latest versions of D2.
>
>
>> Can a class be instantiated on the stack ?
>
> There was a way built in the language to do that (using "scope", it works
> still but it's deprecated), but now you have to use the std library. See the
> std.conv.emplace, but keep in mind it has issues (more than the issues of
> "scope"!) like I think not calling the object destructor.
>
>
>> It appears that D ASSUMES myC is really a myC*(in C++)
>
> Right, in D class instances are always managed by reference, even when you
> allocate them on the stack using the emplace trick.
>
>
>> // but this ALWAYS requires calling the memory allocator
>> // this is what Java does (forces your Class instance onto the Heap)
>
> A difference is that the Oracle Java Garbage Collector has a Eden memory for
> the newly allocated objects that's much faster than the current D GC :-)
>
>
>> Will a struct do?
>
> Sometimes a struct is enough. D structs are managed by value or by pointer,
> but they don't support inheritance. In D structs and classes are different
> (like the memory layout of a class instance is decided by the compiler,
> while struct fields are in memory as you want them, with the alignment you
> desire) and they are used for different purposes.
>
>
>> Does a struct have a constructor (as opposed to an opcall?)
>
> In D2 the struct constructor is this() as for classes.
>
> Bye,
> bearophile
>