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digitalmars.D.learn - Making template instantiations more lazy

reply Per =?UTF-8?B?Tm9yZGzDtnc=?= <per.nordlow gmail.com> writes:
Are there any nearby plans to make more template instantiations 
(especially aggregate members) lazy in DMD?

Are there any specific obstacles against doing that or has it 
just not been prioritized?
Oct 18 2017
parent reply Jonathan M Davis <newsgroup.d jmdavisprog.com> writes:
On Wednesday, October 18, 2017 09:13:47 Per Nordlöw via Digitalmars-d-learn 
wrote:

 Are there any nearby plans to make more template instantiations
 (especially aggregate members) lazy in DMD?

 Are there any specific obstacles against doing that or has it
 just not been prioritized?


Templates are never instantiated unless they're actually... well,
instantiated. So, they're already lazy in that sense. The compiler isn't
pre-emptive with them at all. What exactly about them do you want to be lazy
that isn't?

- Jonathan M Davis
Oct 18 2017
parent reply =?UTF-8?B?Tm9yZGzDtnc=?= <per.nordlow gmail.com> writes:
On Wednesday, 18 October 2017 at 09:32:39 UTC, Jonathan M Davis 
wrote:

 On Wednesday, October 18, 2017 09:13:47 Per Nordlöw via 
 Digitalmars-d-learn wrote:

 Are there any nearby plans to make more template 
 instantiations (especially aggregate members) lazy in DMD?

 Are there any specific obstacles against doing that or has it 
 just not been prioritized?


 Templates are never instantiated unless they're actually... 
 well, instantiated. So, they're already lazy in that sense. The 
 compiler isn't pre-emptive with them at all. What exactly about 
 them do you want to be lazy that isn't?

 - Jonathan M Davis


Member functions of templated containers is my main focus.
Oct 18 2017
parent reply Biotronic <simen.kjaras gmail.com> writes:
On Wednesday, 18 October 2017 at 09:56:33 UTC, Nordlöw wrote:

 On Wednesday, 18 October 2017 at 09:32:39 UTC, Jonathan M Davis 
 wrote:

 On Wednesday, October 18, 2017 09:13:47 Per Nordlöw via 
 Digitalmars-d-learn wrote:

 Are there any nearby plans to make more template 
 instantiations (especially aggregate members) lazy in DMD?

 Are there any specific obstacles against doing that or has it 
 just not been prioritized?


 Templates are never instantiated unless they're actually... 
 well, instantiated. So, they're already lazy in that sense. 
 The compiler isn't pre-emptive with them at all. What exactly 
 about them do you want to be lazy that isn't?

 - Jonathan M Davis


 Member functions of templated containers is my main focus.


Make them templates, that should solve the problem:

struct S(T) {
     void foo()() {
         compileerror;
     }
}
Oct 18 2017
parent reply Per =?UTF-8?B?Tm9yZGzDtnc=?= <per.nordlow gmail.com> writes:
On Wednesday, 18 October 2017 at 10:17:38 UTC, Biotronic wrote:

 Make them templates, that should solve the problem:

 struct S(T) {
     void foo()() {
         compileerror;
     }
 }


Yeah I've thought of that.

I still would like to have it built-in to the compiler.
Oct 18 2017
next sibling parent reply Per =?UTF-8?B?Tm9yZGzDtnc=?= <per.nordlow gmail.com> writes:
On Wednesday, 18 October 2017 at 10:36:41 UTC, Per Nordlöw wrote:

 Yeah I've thought of that.

 I still would like to have it built-in to the compiler.


Would such a change cause any serious breakage?
Oct 18 2017
parent reply Biotronic <simen.kjaras gmail.com> writes:
On Wednesday, 18 October 2017 at 10:55:49 UTC, Per Nordlöw wrote:

 On Wednesday, 18 October 2017 at 10:36:41 UTC, Per Nordlöw 
 wrote:

 Yeah I've thought of that.

 I still would like to have it built-in to the compiler.


 Would such a change cause any serious breakage?


Seems unlikely - when did you last use a function without using 
it? :p

I'm not actually sure why D behaves this way - C++ doesn't. I 
guess there is some value as tests - instantiating the type tests 
that all its methods compile. Not actually sure that's more of a 
positive than a negative, but it's certainly never bothered me.

--
   Biotronic
Oct 18 2017
parent =?UTF-8?B?Tm9yZGzDtnc=?= <per.nordlow gmail.com> writes:
On Wednesday, 18 October 2017 at 11:18:31 UTC, Biotronic wrote:

 I'm not actually sure why D behaves this way - C++ doesn't. I 
 guess there is some value as tests - instantiating the type 
 tests that all its methods compile. Not actually sure that's 
 more of a positive than a negative, but it's certainly never 
 bothered me.

 --
   Biotronic


I wonder if the fix simple (to Walter at least).

It would save container-heavy projects noticeable build time.

Adding () to the member functions did it for mine at least.
Oct 18 2017
prev sibling parent Jonathan M Davis <newsgroup.d jmdavisprog.com> writes:
On Wednesday, October 18, 2017 10:36:41 Per Nordlöw via Digitalmars-d-learn 
wrote:

 On Wednesday, 18 October 2017 at 10:17:38 UTC, Biotronic wrote:

 Make them templates, that should solve the problem:

 struct S(T) {

     void foo()() {

         compileerror;

     }

 }


 Yeah I've thought of that.

 I still would like to have it built-in to the compiler.


If you actually needed all of the member functions to fully exist, that
would make life a lot harder (e.g. if you're doing something with language
bindings and need to guarantee that a particular template instantiation
fully exists). And if you suddenly couldn't guarantee that everything within
a template was instantiated when the template was instantiated, then you
basically have code that looks like it exists but doesn't actually, and that
would make it rather difficult to know what code actually exists, whereas
right now, if you instantiate a template, you know exactly what code then
exists because of that instantiation.

At least with the ability to separately templatize member functions, you can
control what's going on.

- Jonathan M Davis
Oct 18 2017