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digitalmars.D.learn - Array of pointers

reply "Arjan Fetahu" <21arjan hotmail.com> writes:
Hi. I started my first program in D (I have a little experience 
in c).
I wanted to create an array of pointers for creating a node with 
multiple
connections. In C you can make one directly (node *nedePtr[]). 
What is the equivalent for the D's syntax??

Regards
Arjan
Jan 16 2014
parent reply "Namespace" <rswhite4 googlemail.com> writes:
On Thursday, 16 January 2014 at 08:55:43 UTC, Arjan Fetahu wrote:

 Hi. I started my first program in D (I have a little experience 
 in c).
 I wanted to create an array of pointers for creating a node 
 with multiple
 connections. In C you can make one directly (node *nedePtr[]). 
 What is the equivalent for the D's syntax??

 Regards
 Arjan


node*[] nedePtr;
Jan 16 2014
parent reply "Arjan Fetahu" <21arjan hotmail.com> writes:
On Thursday, 16 January 2014 at 09:00:18 UTC, Namespace wrote:

 On Thursday, 16 January 2014 at 08:55:43 UTC, Arjan Fetahu 
 wrote:

 Hi. I started my first program in D (I have a little 
 experience in c).
 I wanted to create an array of pointers for creating a node 
 with multiple
 connections. In C you can make one directly (node *nedePtr[]). 
 What is the equivalent for the D's syntax??

 Regards
 Arjan


 node*[] nedePtr;


Ok. Thank You!
Jan 16 2014
parent reply "Rene Zwanenburg" <renezwanenburg gmail.com> writes:
On Thursday, 16 January 2014 at 09:03:00 UTC, Arjan Fetahu wrote:

 On Thursday, 16 January 2014 at 09:00:18 UTC, Namespace wrote:

 On Thursday, 16 January 2014 at 08:55:43 UTC, Arjan Fetahu 
 wrote:

 Hi. I started my first program in D (I have a little 
 experience in c).
 I wanted to create an array of pointers for creating a node 
 with multiple
 connections. In C you can make one directly (node 
 *nedePtr[]). What is the equivalent for the D's syntax??

 Regards
 Arjan


 node*[] nedePtr;


 Ok. Thank You!


Keep in mind that, unlike in c++, D classes are reference types:

class Node
{
     Node[] nodes; // This is valid
}

Structs are value types though, so using a struct in the above 
example is illegal.
Jan 16 2014
next sibling parent reply "Namespace" <rswhite4 googlemail.com> writes:
On Thursday, 16 January 2014 at 09:47:21 UTC, Rene Zwanenburg 
wrote:

 On Thursday, 16 January 2014 at 09:03:00 UTC, Arjan Fetahu 
 wrote:

 On Thursday, 16 January 2014 at 09:00:18 UTC, Namespace wrote:

 On Thursday, 16 January 2014 at 08:55:43 UTC, Arjan Fetahu 
 wrote:

 Hi. I started my first program in D (I have a little 
 experience in c).
 I wanted to create an array of pointers for creating a node 
 with multiple
 connections. In C you can make one directly (node 
 *nedePtr[]). What is the equivalent for the D's syntax??

 Regards
 Arjan


 node*[] nedePtr;


 Ok. Thank You!


 Keep in mind that, unlike in c++, D classes are reference types:

 class Node
 {
     Node[] nodes; // This is valid
 }

 Structs are value types though, so using a struct in the above 
 example is illegal.


You mean:
----
struct Node {
     Node[] nodes;
}
----

or

----
struct Node {
     Node*[] nodes;
}
----

? Works both.

What's not working is this:
----
struct Node {
	Node node;
}
----
Jan 16 2014
parent reply "Arjan Fetahu" <21arjan hotmail.com> writes:
 Keep in mind that, unlike in c++, D classes are reference 
 types:

 class Node
 {
    Node[] nodes; // This is valid
 }

 Structs are value types though, so using a struct in the above 
 example is illegal.


 You mean:
 ----
 struct Node {
     Node[] nodes;
 }
 ----

 or

 ----
 struct Node {
     Node*[] nodes;
 }
 ----

 ? Works both.

 What's not working is this:
 ----
 struct Node {
 	Node node;
 }
 ----


I wanted to heap allocate Nodes which connect to each other via 
pointers. Since each Node connects to multiple others i came up 
with this solution.

class Node {
      auto content;
      Node*[] nodes;
      //..constructor..
}
Jan 18 2014
parent reply "bearophile" <bearophileHUGS lycos.com> writes:
Arjan Fetahu:


 Since each Node connects to multiple others i came up with this 
 solution.

 class Node {
      auto content;
      Node*[] nodes;
      //..constructor..
 }


Nodes are reference types in D, so probably you don't need to use 
a * for Node. Alternatively use a struct handled by pointer.

"auto content;" can't compile, you need a type, or you have to 
template Node on T and use it for content.

Bye,
bearophile
Jan 18 2014
parent reply "Arjan Fetahu" <21arjan hotmail.com> writes:
 Nodes are reference types in D, so probably you don't need to 
 use a * for Node. Alternatively use a struct handled by pointer.

 "auto content;" can't compile, you need a type, or you have to 
 template Node on T and use it for content.

 Bye,
 bearophile


Youre right, it compiles now, and the object generated is of the 
same size.
I'm still confusing with C. I have some experience with C 
experience, so I still have to learn tamplates.

Thaks for the help.

Arjan
Jan 18 2014
parent "Gary Willoughby" <dev nomad.so> writes:
On Saturday, 18 January 2014 at 14:57:39 UTC, Arjan Fetahu wrote:

 I have some experience with C experience, so I still have to 
 learn tamplates.

 Thaks for the help.

 Arjan


Here's a handy introduction: 
http://nomad.so/2013/07/templates-in-d-explained/
Jan 20 2014
prev sibling next sibling parent Philippe Sigaud <philippe.sigaud gmail.com> writes:
On Thu, Jan 16, 2014 at 10:47 AM, Rene Zwanenburg
<renezwanenburg gmail.com> wrote:


 Keep in mind that, unlike in c++, D classes are reference types:

 class Node
 {
     Node[] nodes; // This is valid
 }

 Structs are value types though, so using a struct in the above example is
 illegal.


That's not true. Indeed:

`struct Node { T value; Node[] children;}`

is my standard way of having trees in D.

The thing is, an array is a reference type and so the compiler is able
to determine `Node` size (T.sizeof + a pointer size, or maybe 2, I
don't remember which).
Jan 16 2014
prev sibling next sibling parent reply Andrej Mitrovic <andrej.mitrovich gmail.com> writes:
On 1/16/14, Philippe Sigaud <philippe.sigaud gmail.com> wrote:

 The thing is, an array is a reference type


Actually it's not, let's not confuse people with the terminology here.
To recap for people new to arrays: an array in D is really just a
struct, e.g.:

struct Array
{
    int* data;
    size_t length;
}

Array myArray;

Once you know this it's easy to understand why passing myArray by
value to a function allows you to change the contents of "data", but
changing what "data" points to or changing the length of the array
will not be reflected at the call site, *unless* you've passed myArray
to a function by reference.
Jan 20 2014
parent =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 01/20/2014 01:58 AM, Andrej Mitrovic wrote:


 On 1/16/14, Philippe Sigaud <philippe.sigaud gmail.com> wrote:

 The thing is, an array is a reference type


 Actually it's not, let's not confuse people with the terminology here.
 To recap for people new to arrays: an array in D is really just a
 struct, e.g.:

 struct Array
 {
      int* data;
      size_t length;
 }

 Array myArray;


I don't remember whether this thread explicitly excludes fixed-length 
arrays but to add to common confusion(s), the above is true only for 
slices (aka dynamic arrays). :) (And, although it shouldn't matter, the 
actual implementation defines the length member before the data member.)

Ali
Jan 20 2014
prev sibling parent Philippe Sigaud <philippe.sigaud gmail.com> writes:
On Mon, Jan 20, 2014 at 10:58 AM, Andrej Mitrovic
<andrej.mitrovich gmail.com> wrote:

 On 1/16/14, Philippe Sigaud <philippe.sigaud gmail.com> wrote:

 The thing is, an array is a reference type


 Actually it's not, let's not confuse people with the terminology here.
 To recap for people new to arrays: an array in D is really just a
 struct, e.g.:


You're right, my bad.
TL;DR: you can do

```
struct Node
{
    T data;
    Node[] children;
}
```
Jan 20 2014