On 05/04/2015 11:07 AM, Robert M. Münch wrote:
> enum A {a, b, c};
>
> enum members1 = __traits(allMembers, A);
> auto members2 = __traits(allMembers, A);
>
> 1. So the (string, string, string) output is based on the expression of
> members1? Meaning, the right-hand-side.
There are many different kinds of tuples in D, only two of which I can
handle:
1) Tuple from std.typecons, which are ordinarily created at run time
2) TypeTuple from std.typetuple, which are compile-time entities
The documentation is not clear that __traits(allMembers) returns a
TypeTuple, which additionally has a bad name.
TypeTuple is great because it enables "compile-time foreach"
(unfortunately, implicitly):
foreach (m; __traits(allMembers, A)) {
// This body is repeated for each member at compile time
}
It is also possible to expand members of a TypeTuple just by putting it
inside an array:
[ __traits(allMembers, A) ]On 05/04/2015 11:07 AM, Robert M. Münch wrote:
> enum A {a, b, c};
>
> enum members1 = __traits(allMembers, A);
> auto members2 = __traits(allMembers, A);
>
> 1. So the (string, string, string) output is based on the expression of
> members1? Meaning, the right-hand-side.
There are many differents kinds of tuples in D, only two of which I can
handle:
1) Tuple from std.typecons, which are ordinarily created at run time
2) TypeTuple from std.typetuple, which are compile-time entities
The documentation is not clear that __traits(allMembers) returns a
TypeTuple, which additionally has a bad name.
TypeTuple is great because it enables "compile-time foreach"
(unfortunately, implicitly):
foreach (m; __traits(allMembers, A)) {
// This body is repeated for each member at compile time
}
It is also possible to expand members of a TypeTuple just by putting it
inside an array:
[ __traits(allMembers, A) ]
However, it should be obvious that all members must have a common type
to be members of the same array. (True to its name, TypeTuple can have
types themselves as well.)
Powerful stuff. :)
> 2. I'm wondering why members1 doesn't has a type at all.
Because it is a TypeTuple of values of various types and even types
themselves.
> So, we don't
> have a compile-time boolean?
I don't understand that one. :(
Ali
However, it should be obvious that all members must have a common type
to be members of the same array. (True to its name, TypeTuple can have
types themselves as well.)
Powerful stuff. :)
> 2. I'm wondering why members1 doesn't has a type at all.
Because it is a TypeTuple of values of various types and even types
themselves.
> So, we don't
> have a compile-time boolean?
I don't understand that one. :(
Ali
