• "Janice Caron" <caron800 googlemail.com> Apr 24 2008
• bearophile <bearophileHUGS lycos.com> Apr 24 2008
• Lionello Lunesu <lio lunesu.remove.com> May 04 2008
• Fawzi Mohamed <fmohamed mac.com> May 08 2008
• "Koroskin Denis" <2korden gmail.com> May 08 2008
• "Janice Caron" <caron800 googlemail.com> May 08 2008

I would like to be able to allocate a dynamic array on the stack.
The following compiles, but does not achieve the desired effect:

    int n = 100;
    scope array = new int[n];

The array is allocated on the heap, not the stack. I would like it to
be allocated on the stack.

I would also like to be able to create uninitialised dynamic arrays:

    // on the heap
    auto array = new int[n] = void;

    // on the stack
    scope array = new int[n] = void;

Note that the last one of these can be implemented in machine code
merely by decrementing the stack pointer! (Well - almost. array.ptr
and array.length would still need to be assigned, but I can live with
that).

Obviously, increasing the length of a scope array would have to be illegal!

Finally, I want to be able to increase the length of an array without
initialising the new elements:

    array.length = 100 = void;

(The syntax of the last one leaves a bit to be desired, but I can't
think of anything better off hand, right now).

Does anyone know if any or all of these are already the subject of
enhancement request? Does anyone else want any of these? Is there any
reason why I shouldn't add this to bugzilla?

Janice Caron Wrote:

 I would like to be able to allocate a dynamic array on the stack.
 I would also like to be able to create uninitialised dynamic arrays:


In the "extra" module in my D libs there are functions for that:
http://www.fantascienza.net/leonardo/so/libs_d.zip


 Finally, I want to be able to increase the length of an array without
 initialising the new elements:


This needs more work...

Bye,
bearophile

Janice Caron wrote:
 I would like to be able to allocate a dynamic array on the stack.
 The following compiles, but does not achieve the desired effect:
 
     int n = 100;
     scope array = new int[n];


Maybe this could be made to work as well:

#int n = 100;
#int[n] array;

L.

On 2008-05-08 16:18:04 +0200, "Janice Caron" <caron800 googlemail.com> said:

 2008/5/8 Koroskin Denis <2korden gmail.com>:
 That's not a dynamic allocation, i.e. you cannot do like this:
 
 void foo(int i)
 {
 int[i] array;
 }
 
 And I don't know of any language, that could do that.


 C99.
 
 http://www.comeaucomputing.com/techtalk/c99/#variablelengtharrays


also fortran can do this :)
Indeed it can be useful.
An ugly side effect is that then the stack can grow a lot and you hit 
the default ulimit (ifort does it).

On Sun, 04 May 2008 19:22:29 +0400, Lionello Lunesu  
<lio lunesu.remove.com> wrote:

 Janice Caron wrote:
 I would like to be able to allocate a dynamic array on the stack.
 The following compiles, but does not achieve the desired effect:
      int n = 100;
     scope array = new int[n];


 Maybe this could be made to work as well:

 #int n = 100;
 #int[n] array;

 L.


That's not a dynamic allocation, i.e. you cannot do like this:

void foo(int i)
{
    int[i] array;
}

And I don't know of any language, that could do that. Problem is, you have  
to deal with stack alignment.
C/C++/D use "static stack alignment", i.e. it is mostly manager at compile  
time.
The only way of manipulating it at run time is a recursion. Asm statements  
don't help, because
for each "asm { push something; }" statement there is corresponding hidden  
"asm { pop; }" added.

 Janice Caron wrote:
 I would also like to be able to create uninitialised dynamic arrays:


    // on the heap
    auto array = new int[n] = void;

    // on the stack
    scope array = new int[n] = void;


I would rather stick with capacity member, i.e:

char[] array;
array.length = 100;   // zeroes out 100 elements
array.capacity = 200; // 0..100 are zeroes, 101..200 hold garbage

capacity can be implemented as a member function, rather than a field,
so that (array.sizeof == 8) still true.

2008/5/8 Koroskin Denis <2korden gmail.com>:
  That's not a dynamic allocation, i.e. you cannot do like this:

  void foo(int i)
  {
    int[i] array;
  }

  And I don't know of any language, that could do that.


C99.

http://www.comeaucomputing.com/techtalk/c99/#variablelengtharrays