On Monday, 16 September 2013 at 17:50:16 UTC, Maxim Fomin wrote:
On Monday, 16 September 2013 at 16:50:43 UTC, Namespace wrote:
On Monday, 16 September 2013 at 15:47:36 UTC, ilya-stromberg
wrote:
On Monday, 16 September 2013 at 15:12:05 UTC, Maxim Fomin
wrote:
On Monday, 16 September 2013 at 10:29:12 UTC, matovitch
wrote:
All your examples are great, thank you ! Is there a way to
omit validate such that the compiler would call it
implicitly ?
For example :
class C {
...
}
void fun(@nonNull C c) {
...
};
C c;
fun(c); //compilation error since C is null
No, this isn't doable with UDAs because what you want
requires runtime check. It is doable using other language
features.
It's intresting how can I check that pointer is not null at
the compile time. Can you print a example, please?
I know that we can use contract programming, but it requires
runtime check.
That isn't possible. ;)
Similar effect can be achieved by different way. If some
function takes S as parameter, one cannot pass directly
instance of A or null - error will be issued which is some sort
of compile-time protection.
class A
{
int i;
}
struct S
{
A a;
A getA()
{
if (a is null)
a = new A;
return a;
}
alias getA this;
}
void main()
{
S s;
assert (s.i is 0);
S ss = S.init;
assert (ss.i is 0);
}
Unfortunately D does not have non-nullable classes which is a
problem #1. Ideally structs should have default constructors
(hello to those who miss them - problem #2) which could
initialize class instance. Since they are absent, wrapping
struct can be enhanced by inserting disabled constructor to
ensure that no default struct instances with null references
are created. However, since disabled constructors are also
flawed (they don't prevent from producing T.init values by
design and in some situations dmd is not smart enough to detect
other cases by mistake) which is a problem #3, non-null classes
can be simulated by code above using alias this + rt check. At
least this works with two most problematic cases of struct
initilialization: without initializer and with T.init value.
Yes, I know. Search for my name and not null, you will find many
topics.
I hate this NotNull struct hack. It is the same crap as the
current scope solution. BTW: I'm curious which built-in feature
will be removed next, maybe AA?
An annotation like Foo! f would be much nicer than NotNull!Foo or
@NotNull Foo, but it would be an agreement.
And I agree absolute, to disable default CTor's by struct's was a
huge mistake. But D is full of those. ;)
