On Wed, 28 Dec 2011 15:00:10 +0100, Gor Gyolchanyan
<[email protected]> wrote:
This is something I was thinking about for a long time now.
There seems to be absolutely no difference between T, const(T) and
immutable(T) if T is a compile-time value (a enum or a local in CTFE).
The possibility to mutate compile-time values (at compile time, of
course) would allow very convenient techniques to be used for a number
of purposes.
And since in my hypothetical D compile-time data can be mutated, then
a compile-time static this is required (especially for the next
example).
For instance, here's something I'd love to be able to do:
class Base
{
mixin template Register()
{
ctStaticThis() // a placeholder for the real compile-time static
this
{
Derived = TypeTuple!(Derived, typeof(this));
}
}
enum Derived = TypeTuple!();
}
class Derived1: Base
{
mixin Register;
}
class Derived2: Base
{
mixin Register;
}
static assert(is(Base.Derived == TypeTuple!(Base, Derived1, Derived2)));
Similar things would allow to quickly build extremely powerful and
useful compile-time information, which is currently not possible to
build.
If mutable compile-time data is implemented, the entire compile-time
computation in D would become just like the run-time one.
I'd really like to see such a construct.
enum __iota;
enum Masks
{
A = (1 << __iota++),
B = (1 << __iota++),
C = (1 << __iota++),
DMask = (0b11 << __iota),
D0 = (1 << __iota++),
D1 = (1 << __iota++),
}
static assert(__iota <= 32);
Now this would depend on the order of semantic so it's not feasible.
