• Dave Jones (4/4) Oct 18 2017 Poking around in the source code for emplace and I noticed...
• Dave Jones (2/6) Oct 18 2017 sorry meant to put this in learn
• Moritz Maxeiner (5/9) Oct 18 2017 It means that any argument (that is an element of args) will be
• Dave Jones (4/15) Oct 18 2017 So it's just to make sure any "ref" in the eventual call to Ts
• Jonathan M Davis (8/25) Oct 18 2017 That's likely the main reason in this case, since losing the ref-ness co...
• Dave Jones (3/12) Oct 19 2017 Makes sense, thanks.

Dave Jones <dave jones.com> writes:

Poking around in the source code for emplace and I noticed...

T* emplace(T, Args...)(T* chunk, auto ref Args args)

what does the "auto ref" do in this situiation? Cant seem to find 
any explanation in the docs.

Dave Jones <dave jones.com> writes:

On Wednesday, 18 October 2017 at 21:38:41 UTC, Dave Jones wrote:
 Poking around in the source code for emplace and I noticed...

 T* emplace(T, Args...)(T* chunk, auto ref Args args)

 what does the "auto ref" do in this situiation? Cant seem to 
 find any explanation in the docs.

sorry meant to put this in learn

Moritz Maxeiner <moritz ucworks.org> writes:

On Wednesday, 18 October 2017 at 21:38:41 UTC, Dave Jones wrote:
 Poking around in the source code for emplace and I noticed...

 T* emplace(T, Args...)(T* chunk, auto ref Args args)

 what does the "auto ref" do in this situiation? Cant seem to 
 find any explanation in the docs.

It means that any argument (that is an element of args) will be 
passed by reference if and only if it's an lvalue (has a memory 
address that can be taken) (it'll be passed by value otherwise).

https://dlang.org/spec/template.html#auto-ref-parameters

Dave Jones <dave jones.com> writes:

On Wednesday, 18 October 2017 at 22:16:32 UTC, Moritz Maxeiner 
wrote:
 On Wednesday, 18 October 2017 at 21:38:41 UTC, Dave Jones wrote:
 Poking around in the source code for emplace and I noticed...

 T* emplace(T, Args...)(T* chunk, auto ref Args args)

 what does the "auto ref" do in this situiation? Cant seem to 
 find any explanation in the docs.

 It means that any argument (that is an element of args) will be 
 passed by reference if and only if it's an lvalue (has a memory 
 address that can be taken) (it'll be passed by value otherwise).

 https://dlang.org/spec/template.html#auto-ref-parameters

So it's just to make sure any "ref" in the eventual call to Ts 
constructor is also reflected in the call to emplace?

Jonathan M Davis <newsgroup.d jmdavisprog.com> writes:

On Thursday, October 19, 2017 00:00:54 Dave Jones via Digitalmars-d wrote:
 On Wednesday, 18 October 2017 at 22:16:32 UTC, Moritz Maxeiner

 wrote:
 On Wednesday, 18 October 2017 at 21:38:41 UTC, Dave Jones wrote:
 Poking around in the source code for emplace and I noticed...

 T* emplace(T, Args...)(T* chunk, auto ref Args args)

 what does the "auto ref" do in this situiation? Cant seem to
 find any explanation in the docs.

 It means that any argument (that is an element of args) will be
 passed by reference if and only if it's an lvalue (has a memory
 address that can be taken) (it'll be passed by value otherwise).

 https://dlang.org/spec/template.html#auto-ref-parameters

 So it's just to make sure any "ref" in the eventual call to Ts
 constructor is also reflected in the call to emplace?

That's likely the main reason in this case, since losing the ref-ness could
definitely cause issues with some constructors, but auto ref is frequently
used simply to avoid copying lvalues while not requiring lvalues (since if
ref is used, the argument must be an lvalue, and if ref is not used, the
argument will be copied if it's an lvalue; it will be moved if it's an
rvalue). D never binds rvalues to ref like C++ does with const T&.

- Jonathan M Davis

Dave Jones <dave jones.com> writes:

On Thursday, 19 October 2017 at 01:05:28 UTC, Jonathan M Davis 
wrote:
 On Thursday, October 19, 2017 00:00:54 Dave Jones via

 That's likely the main reason in this case, since losing the 
 ref-ness could definitely cause issues with some constructors, 
 but auto ref is frequently used simply to avoid copying lvalues 
 while not requiring lvalues (since if ref is used, the argument 
 must be an lvalue, and if ref is not used, the argument will be 
 copied if it's an lvalue; it will be moved if it's an rvalue). 
 D never binds rvalues to ref like C++ does with const T&.

 - Jonathan M Davis

Makes sense, thanks.