Re: Growing multidimensional dynamic arrays

[KillerSponge]

On Monday, 8 October 2012 at 13:56:00 UTC, Ali Çehreli wrote:
I don't see the need for 'new' nor the use of a pointer, so I 
will not use them (yet): :)


import std.stdio;

struct X
{
int i;
}

void main()
{
X[][] listOfLists;

auto otherListOfX = [ X(1), X(2), X(3) ];
auto newListForArbitraryReason = true;

foreach (x; otherListOfX) {
if (newListForArbitraryReason) {
X[] newList = [ x ];
listOfLists ~= newList;
}
}

writeln(listOfLists);
}

The body of foreach can be shorter:

listOfLists ~= [ x ];

Also note that

- There is no need for the semicolon at the end of the struct 
definition.


- $ is not a valid index value. The last element is indexed by 
$-1.


Ali


Ah, that works great (even with pointers ;)! Thanks a lot! :) It 
seems so obvious now.


And the use of $ was indeed a stupid mistake on my part. I guess 
I was confused because of the way it is often used in slicing. I 
really should pay attention to that :)

Re: Growing multidimensional dynamic arrays

[Ali Çehreli]

On 10/08/2012 06:12 AM, KillerSponge wrote:

Hi all,

This seems like something that should be possible: how do I grow
multidimensional arrays?

I want something like this:

struct X{ ... };
X*[][] listOfLists;
foreach ( x ; otherListOfX ) {
if ( newListForArbitraryReason ) {
listOfLists ~= new X*[];
}

listOfLists[$] ~= x;
}

Now, this doesn't compile, because I _have_ to give a size to new
X*[](arbitrary_number), and the listOfLists[$] ~= x; line never works
(hangs at runtime).

So, how would I go about doing this? My apologies if this is something
really obvious.


I don't see the need for 'new' nor the use of a pointer, so I will not 
use them (yet): :)


import std.stdio;

struct X
{
int i;
}

void main()
{
X[][] listOfLists;

auto otherListOfX = [ X(1), X(2), X(3) ];
auto newListForArbitraryReason = true;

foreach (x; otherListOfX) {
if (newListForArbitraryReason) {
X[] newList = [ x ];
listOfLists ~= newList;
}
}

writeln(listOfLists);
}

The body of foreach can be shorter:

listOfLists ~= [ x ];

Also note that

- There is no need for the semicolon at the end of the struct definition.

- $ is not a valid index value. The last element is indexed by $-1.

Ali

--
D Programming Language Tutorial: http://ddili.org/ders/d.en/index.html

Growing multidimensional dynamic arrays

[KillerSponge]

Hi all,

This seems like something that should be possible: how do I grow 
multidimensional arrays?


I want something like this:

struct X{ ... };
X*[][] listOfLists;
foreach ( x ; otherListOfX ) {
   if ( newListForArbitraryReason ) {
  listOfLists ~= new X*[];
   }

   listOfLists[$] ~= x;
}

Now, this doesn't compile, because I _have_ to give a size to new 
X*[](arbitrary_number), and the listOfLists[$] ~= x; line never 
works (hangs at runtime).


So, how would I go about doing this? My apologies if this is 
something really obvious.