Re: how do I check if a member of a T has a member ?
On Sunday, 13 September 2015 at 17:34:11 UTC, BBasile wrote:
On Sunday, 13 September 2015 at 17:24:20 UTC, Laeeth Isharc
wrote:
On Sunday, 13 September 2015 at 17:09:57 UTC, wobbles wrote:
Use __traits(compiles, date.second)?
Thanks.
This works:
static if (__traits(compiles, { T bar; bar.date.hour;}))
pragma(msg,"hour");
else
pragma(msg,"nohour");
can't you use 'hasMember' (either with __traits() or
std.traits.hasMember)? It's more idiomatic than checking if
it's compilable.
I'll check again in a bit, but I seem to recall hasMember didn't
work. I would like to get the type of a member of a type, and I
think hasMember!(T.bar.date","hour") didn't work for that.
Possibly it does work and I messed it up somehow, or it doesn't
work and there is a more elegant way.
Someone ought to write a tutorial showing how to use the good
stuff we have to solve real problems. Eg an annotated babysteps
version of Andrei's allocator talk. I can't do it as too much on
my plate.
Re: how do I check if a member of a T has a member ?
On Monday, 14 September 2015 at 14:05:01 UTC, Laeeth Isharc wrote: On Sunday, 13 September 2015 at 17:34:11 UTC, BBasile wrote: On Sunday, 13 September 2015 at 17:24:20 UTC, Laeeth Isharc wrote: [...] can't you use 'hasMember' (either with __traits() or std.traits.hasMember)? It's more idiomatic than checking if it's compilable. I'll check again in a bit, but I seem to recall hasMember didn't work. I would like to get the type of a member of a type, and I think hasMember!(T.bar.date","hour") didn't work for that. Possibly it does work and I messed it up somehow, or it doesn't work and there is a more elegant way. You mean hasMember!(typeof(T.bar.date), "hour"), right?
Re: how do I check if a member of a T has a member ?
On Monday, 14 September 2015 at 14:21:12 UTC, John Colvin wrote: On Monday, 14 September 2015 at 14:05:01 UTC, Laeeth Isharc wrote: On Sunday, 13 September 2015 at 17:34:11 UTC, BBasile wrote: On Sunday, 13 September 2015 at 17:24:20 UTC, Laeeth Isharc wrote: [...] can't you use 'hasMember' (either with __traits() or std.traits.hasMember)? It's more idiomatic than checking if it's compilable. I'll check again in a bit, but I seem to recall hasMember didn't work. I would like to get the type of a member of a type, and I think hasMember!(T.bar.date","hour") didn't work for that. Possibly it does work and I messed it up somehow, or it doesn't work and there is a more elegant way. You mean hasMember!(typeof(T.bar.date), "hour"), right? Ahh. Probably that was why (I will check it shortly). Why do I need to do a typeof? What kind of thing is T.bar.date before the typeof given that T is a type?
Re: how do I check if a member of a T has a member ?
On Monday, 14 September 2015 at 15:04:00 UTC, Laeeth Isharc wrote: On Monday, 14 September 2015 at 14:21:12 UTC, John Colvin wrote: On Monday, 14 September 2015 at 14:05:01 UTC, Laeeth Isharc wrote: On Sunday, 13 September 2015 at 17:34:11 UTC, BBasile wrote: On Sunday, 13 September 2015 at 17:24:20 UTC, Laeeth Isharc wrote: [...] can't you use 'hasMember' (either with __traits() or std.traits.hasMember)? It's more idiomatic than checking if it's compilable. I'll check again in a bit, but I seem to recall hasMember didn't work. I would like to get the type of a member of a type, and I think hasMember!(T.bar.date","hour") didn't work for that. Possibly it does work and I messed it up somehow, or it doesn't work and there is a more elegant way. You mean hasMember!(typeof(T.bar.date), "hour"), right? Ahh. Probably that was why (I will check it shortly). Why do I need to do a typeof? What kind of thing is T.bar.date before the typeof given that T is a type? T.bar.date is just a symbol. If you tried to actually access it then it would have to be a compile-time construct or be a static member/method, but it's perfectly OK to ask what type it has or what size it has. The simple story: hasMember takes a type as its first argument. T.bar.date isn't a type, it's a member of a member of a type. To find out what type it is, use typeof.
how do I check if a member of a T has a member ?
can I check if a member of a T has a member without using a mixin?
hid_t createDataType(T)()
if (__traits(isSame, TemplateOf!(T), PriceBar))
{
auto tid=H5T.create(H5TClass.Compound,T.sizeof);
enum offsetof(alias type, string field) = mixin(type.stringof
~"."~field~".offsetof");
H5T.insert(tid, "date", offsetof!(T,"date"),
createDataType!(KalDate));
static if(hasMember!(T,"open"))
H5T.insert(tid,"open",offsetof!(T,"open"),mapDtoHDF5Type("double"));
}
I would like to check if date has a member called second.
Thanks.
Re: how do I check if a member of a T has a member ?
On Sunday, 13 September 2015 at 17:24:20 UTC, Laeeth Isharc wrote:
On Sunday, 13 September 2015 at 17:09:57 UTC, wobbles wrote:
Use __traits(compiles, date.second)?
Thanks.
This works:
static if (__traits(compiles, { T bar; bar.date.hour;}))
pragma(msg,"hour");
else
pragma(msg,"nohour");
can't you use 'hasMember' (either with __traits() or
std.traits.hasMember)? It's more idiomatic than checking if it's
compilable.
Re: how do I check if a member of a T has a member ?
On Sunday, 13 September 2015 at 16:46:54 UTC, Laeeth Isharc wrote:
can I check if a member of a T has a member without using a
mixin?
hid_t createDataType(T)()
if (__traits(isSame, TemplateOf!(T), PriceBar))
{
auto tid=H5T.create(H5TClass.Compound,T.sizeof);
enum offsetof(alias type, string field) = mixin(type.stringof
~"."~field~".offsetof");
H5T.insert(tid, "date", offsetof!(T,"date"),
createDataType!(KalDate));
static if(hasMember!(T,"open"))
H5T.insert(tid,"open",offsetof!(T,"open"),mapDtoHDF5Type("double"));
}
I would like to check if date has a member called second.
Thanks.
Use __traits(compiles, date.second)?
Re: how do I check if a member of a T has a member ?
On Sunday, 13 September 2015 at 17:09:57 UTC, wobbles wrote:
Use __traits(compiles, date.second)?
Thanks.
This works:
static if (__traits(compiles, { T bar; bar.date.hour;}))
pragma(msg,"hour");
else
pragma(msg,"nohour");
