Re: Get pointer or reference of an element in Array(struct)

2017-12-11 Thread Arun Chandrasekaran via Digitalmars-d-learn 
On Saturday, 9 December 2017 at 19:26:26 UTC, David Nadlinger 
wrote:

but "free" references don't exist in the language.


To the point! Thanks!

Re: Get pointer or reference of an element in Array(struct)

2017-12-09 Thread Azi Hassan via Digitalmars-d-learn 
On Saturday, 9 December 2017 at 06:46:27 UTC, Arun Chandrasekaran 
wrote:

On Saturday, 9 December 2017 at 06:38:46 UTC, anonymous wrote:
On Saturday, 9 December 2017 at 06:15:16 UTC, Arun 
Chandrasekaran wrote:
Is there a way to get the pointer or reference of an element 
in Array(T)?

[...]

auto d2 = gallery[0];


auto d2 = &gallery[0];


Thanks. Just curious why reference can't be obtained here. 
Saves nasty null checks in most places.


In D, structs are passed by value unless otherwise specified. 
Using a class will yield the expected result.

Re: Get pointer or reference of an element in Array(struct)

2017-12-09 Thread David Nadlinger via Digitalmars-d-learn 
On Saturday, 9 December 2017 at 06:46:27 UTC, Arun Chandrasekaran 
wrote:
Thanks. Just curious why reference can't be obtained here. 
Saves nasty null checks in most places.


D simply doesn't have a (C++-style) concept of references as part 
of the type. Arguments can be passed by reference - hence the 
`ref` keyword -, but "free" references don't exist in the 
language.


The ref in foreach loop variables can be conceptually thought of 
as a parameter to the loop body as well. (For opApply-based 
iteration, the loop body indeed gets turned into a function; for 
"plain" iteration the compiler AST internally has special ref 
variables, but they are not visible to the language.)


 -David

Re: Get pointer or reference of an element in Array(struct)

2017-12-08 Thread Arun Chandrasekaran via Digitalmars-d-learn 

On Saturday, 9 December 2017 at 06:38:46 UTC, anonymous wrote:
On Saturday, 9 December 2017 at 06:15:16 UTC, Arun 
Chandrasekaran wrote:
Is there a way to get the pointer or reference of an element 
in Array(T)?

[...]

auto d2 = gallery[0];


auto d2 = &gallery[0];


Thanks. Just curious why reference can't be obtained here. Saves 
nasty null checks in most places.

Re: Get pointer or reference of an element in Array(struct)

2017-12-08 Thread anonymous via Digitalmars-d-learn 
On Saturday, 9 December 2017 at 06:15:16 UTC, Arun Chandrasekaran 
wrote:
Is there a way to get the pointer or reference of an element in 
Array(T)?

[...]

auto d2 = gallery[0];


auto d2 = &gallery[0];

Get pointer or reference of an element in Array(struct)

2017-12-08 Thread Arun Chandrasekaran via Digitalmars-d-learn 
Is there a way to get the pointer or reference of an element in 
Array(T)?


https://run.dlang.io/gist/70fd499afe8438d4877f57aec90c3091?compiler=dmd

The assertion seems to fail below. Value copy is not is intended 
here.


module test;

void main()
{
struct Data
{
int id;
}

import std.container.array;
Array!Data gallery;

Data d1;
gallery.insertBack(d1);

auto d2 = gallery[0];
d2.id = 1;
assert(d2.id == gallery[0].id, "neither ref nor pointer");
}