• Ellery Newcomer (7/7) Sep 07 2012 alright what's the deal?
• bearophile (12/13) Sep 07 2012 This is one of the "clean" ways to do it:
• Timon Gehr (8/21) Sep 07 2012 I prefer this:
• bearophile (8/14) Sep 08 2012 This allocates past the size of the array, the information to
• Timon Gehr (2/17) Sep 08 2012 Wasn't aware that this got fixed. Thanks!
• Artur Skawina (12/28) Sep 08 2012 Yeah, this would be (the) one reason for introducing reference variables

Ellery Newcomer <ellery-newcomer utulsa.edu> writes:

alright what's the deal?

void main () {
     alias int[3][4] fooz;
     int[3][4]* i = new fooz;
}


wiz.d(6): Error: new can only create structs, dynamic arrays or class 
objects, not int[3LU][4LU]'s

"bearophile" <bearophileHUGS lycos.com> writes:

Ellery Newcomer:

 alright what's the deal?

This is one of the "clean" ways to do it:

void main () {
     static struct Mat {
         int[3][4] m;
         alias m this;
     }
     Mat* fooz = new Mat;
     fooz[1][3] = 5;
}


Bye,
bearophile

Timon Gehr <timon.gehr gmx.ch> writes:

On 09/08/2012 04:19 AM, bearophile wrote:
 Ellery Newcomer:

 alright what's the deal?

 This is one of the "clean" ways to do it:

 void main () {
      static struct Mat {
          int[3][4] m;
          alias m this;
      }
      Mat* fooz = new Mat;
      fooz[1][3] = 5;

This may corrupt your heap.

 }


 Bye,
 bearophile

I prefer this:

void main(){
     alias int[3][4] fooz;
     int[3][4]* i = (new fooz[1]).ptr;
}

But I think the original example should just work.

"bearophile" <bearophileHUGS lycos.com> writes:

Timon Gehr:

 This may corrupt your heap.

I usually don't put the alis this...


 I prefer this:

 void main(){
     alias int[3][4] fooz;
     int[3][4]* i = (new fooz[1]).ptr;
 }

This allocates past the size of the array, the information to 
append to the array of fooz. It's a very little amount of memory.

Since some weeks, if you allocate a single struct that contains a 
single fixed size array, that memory is not allocated.

Bye,
bearophile

Timon Gehr <timon.gehr gmx.ch> writes:

On 09/08/2012 01:21 PM, bearophile wrote:
 Timon Gehr:

 This may corrupt your heap.

 I usually don't put the alis this...


 I prefer this:

 void main(){
     alias int[3][4] fooz;
     int[3][4]* i = (new fooz[1]).ptr;
 }

 This allocates past the size of the array, the information to append to
 the array of fooz. It's a very little amount of memory.

 Since some weeks, if you allocate a single struct that contains a single
 fixed size array, that memory is not allocated.

 Bye,
 bearophile

Wasn't aware that this got fixed. Thanks!

Artur Skawina <art.08.09 gmail.com> writes:

On 09/08/12 05:27, Timon Gehr wrote:
 On 09/08/2012 04:19 AM, bearophile wrote:
 Ellery Newcomer:

 alright what's the deal?

 This is one of the "clean" ways to do it:

 void main () {
      static struct Mat {
          int[3][4] m;
          alias m this;
      }
      Mat* fooz = new Mat;
      fooz[1][3] = 5;

 
 This may corrupt your heap.

Yeah, this would be (the) one reason for introducing reference variables
to the language; it's too easy right now to introduce such bugs (and if
the code happens to compile it will just silently return bogus results).

It's a bit late for such a change (and making it more backwards compatible
by having refs that implicitly convert to pointers would be even more
confusing while not solving the problem).
Restricting certain operations on pointers-to-custom-types might work, but
also carries a cost (eg indexing pointers to such types wouldn't be possible
unless via a (temp) slice) as there probably already is code out there that 
accesses arrays of indexable-structs via pointers...

artur