Re: How does this template work?
On Sunday, 16 June 2019 at 15:11:29 UTC, Robert M. Münch wrote:
How does the observerObject Template and function work? I'm
struggling because both use the same name and how is the
template parameter R deduced/where is it coming from? Looks
like it's somehow implicitly deduced.
Eponymous templates:
https://dlang.org/spec/template.html#implicit_template_properties
"Templated types" are actually particular cases of eponymous
templates:
https://dlang.org/spec/template.html#StructTemplateDeclaration
class ObserverObject(R, E...) {...}
is equivalent to
tempalte ObserverObject(R, E...)
{
class ObserverObject(R, E...) {...}
}
So this is I think how everything is made to work with the same
compiler engine, both individual "templated types" and "eponymous
templates".
It's considered idiomatic, but if you don't like it in your case,
it's very easy for the author to avoid it: just make the names
different in any way.
template Observer(E)
{
ObserverObject!(R, E) Object(R)(R range)
{
return new ObserverObject!(R, E)(range);
}
}
auto observer = Observer!int.Object(TestObserver());
Re: How does this template work?
On 2019-06-17 20:53:28 +, aliak said: Less typing for one. Otherwise you'd have to write: auto observer = observerObject!int.observerObject(TestObserver()); Since code is many times more read than written I will never understand why the syntax is polluted to save some keystrokes, making it much harded for others who don't have 800 pages special cases in their mind to read the code. One explicit alias or so would be OK too for cases where such a declaration is needed more than once. But anyway, thanks. -- Robert M. Münch http://www.saphirion.com smarter | better | faster
Re: How does this template work?
On Monday, 17 June 2019 at 18:25:24 UTC, Robert M. Münch wrote: On 2019-06-16 15:14:37 +, rikki cattermole said: observerObject is an eponymous template. What this means (in essence) is the symbol inside the template block == template block. Hmm... ok. Is there any reason to have these "eponymous templates"? I don't see any benefit... Less typing for one. Otherwise you'd have to write: auto observer = observerObject!int.observerObject(TestObserver());
Re: How does this template work?
On 2019-06-16 15:14:37 +, rikki cattermole said: observerObject is an eponymous template. What this means (in essence) is the symbol inside the template block == template block. Hmm... ok. Is there any reason to have these "eponymous templates"? I don't see any benefit... -- Robert M. Münch http://www.saphirion.com smarter | better | faster
How does this template work?
How does the observerObject Template and function work? I'm struggling
because both use the same name and how is the template parameter R
deduced/where is it coming from? Looks like it's somehow implicitly
deduced.
class ObserverObject(R, E...){...}
template observerObject(E)
{
ObserverObject!(R, E) observerObject(R)(R range)
{
return new ObserverObject!(R, E)(range);
}
}
struct TestObserver {...}
auto observer = observerObject!int(TestObserver());
--
Robert M. Münch
http://www.saphirion.com
smarter | better | faster
Re: How does this template work?
On 17/06/2019 3:11 AM, Robert M. Münch wrote:
How does the observerObject Template and function work? I'm struggling
because both use the same name and how is the template parameter R
deduced/where is it coming from? Looks like it's somehow implicitly
deduced.
class ObserverObject(R, E...){...}
template observerObject(E)
{
ObserverObject!(R, E) observerObject(R)(R range)
{
return new ObserverObject!(R, E)(range);
}
}
struct TestObserver {...}
auto observer = observerObject!int(TestObserver());
observerObject is an eponymous template.
What this means (in essence) is the symbol inside the template block ==
template block.
Yes R is being inferred by the argument.
