I've just started working with D.  I'm very pleased with what I see.
 I have noticed something that might be a bug though.  I'm not sure the
correct protocol for reporting potential bugs, so I figured I'd send my
thoughts here first.

    The following code apparently worked in earlier versions of D (I
haven't tested this, but have seen similar code in other threads):

import std.stdio;

void main ()
{
    int[int][int]	array;

    array[12][15]++;
}

    I compiled this with:

    gdc test.d -o test

    And when run it results in an ArrayBoundsError exception being
thrown.  After reading the message boards I came across a change in 0.19
that I think is responsible.  Apparently associative arrays would add
entries just by being referenced.  0.19 removed this behavior and they
now throw ArrayBoundsError exceptions.  This makes perfect sense to me
and is the right behavior (at least it seems to be to me).  The problem
is that the first access in the multidimensional array modification is
being treated as just that, and access, and not an lvalue.  At least
that's what I think is happening.  This seams like an unintentional side
effect of the change.  If I change the code to initialize the inner
associative array then it works but is cumbersome:

import std.stdio;

void main ()
{
    static int[int]	init;
    int[int][int]	array;

    array[12] = init;

    array[12][15]++;
}

    That version works fine in 0.19, but means that every time you want
to modify a multidimensional associative array you need to check each
inner dimension to make sure it's initialized and initialize it if it is
not.

    Thank you,
        Anton Staaf

On Thu, 10 Aug 2006 16:31:45 -0700, Anton V Staaf wrote:

...

> every time you want
> to modify a multidimensional associative array you need to check each
> inner dimension to make sure it's initialized and initialize it if it is
> not.

Yes, that is what we need to do for now. Maybe in v2.0 of D we will have some help from the compiler. And BTW, this applies to non-AA dynamic-length arrays too.

-- 
Derek
(skype: derek.j.parnell)
Melbourne, Australia
"Down with mediocrity!"
11/08/2006 10:37:53 AM

Anton V Staaf wrote:
>     I've just started working with D.  I'm very pleased with what I see.
>  I have noticed something that might be a bug though.  I'm not sure the
> correct protocol for reporting potential bugs, so I figured I'd send my
> thoughts here first.
> 
>     The following code apparently worked in earlier versions of D (I
> haven't tested this, but have seen similar code in other threads):
> 
> import std.stdio;
> 
> void main ()
> {
>     int[int][int]	array;
> 
>     array[12][15]++;
> }
> 
>     I compiled this with:
> 
>     gdc test.d -o test
> 
>     And when run it results in an ArrayBoundsError exception being
> thrown.  After reading the message boards I came across a change in 0.19
> that I think is responsible.  Apparently associative arrays would add
> entries just by being referenced.  0.19 removed this behavior and they
> now throw ArrayBoundsError exceptions.  This makes perfect sense to me
> and is the right behavior (at least it seems to be to me).

Personally, I'd prefer if use of AAs as an lvalue inserted the element if it didn't exist and then returned a reference to this element, while use of AAs as an rvalue simply returned the init value of the contained type and didn't modify the AA.  'in' could still be used for testing whether the AA contained the value or not.  But I suppose that's water under the bridge at this point ;-)


Sean

Anton V Staaf wrote:

> thrown.  After reading the message boards I came across a change in 0.19
> that I think is responsible.  Apparently associative arrays would add

I was actually just looking for the changelog yesterday. I found:

  D 0.163 (current) back to D 0.140 (Nov 23, 2005)
  http://www.digitalmars.com/d/changelog.html

  D 0.139 (Nov 7, 2005) back to D 0.43 (Sep 28, 2002)
  http://www.digitalmars.com/d/changelog1.html

However I could not find a link for anything as far back as D 0.19. I tried changelog2.html but got dropped back on the homepage. Since you were asking about D 0.19 I thought I might ask if you found anything before Sep 2002?

nobody wrote:

> Anton V Staaf wrote:
> 
>> thrown.  After reading the message boards I came across a change in 0.19 that I think is responsible.  Apparently associative arrays would add
> 
> I was actually just looking for the changelog yesterday. I found:
> 
>    D 0.163 (current) back to D 0.140 (Nov 23, 2005)
>    http://www.digitalmars.com/d/changelog.html
> 
>    D 0.139 (Nov 7, 2005) back to D 0.43 (Sep 28, 2002)
>    http://www.digitalmars.com/d/changelog1.html
> 
> However I could not find a link for anything as far back as D 0.19. I tried changelog2.html but got dropped back on the homepage. Since you were asking about D 0.19 I thought I might ask if you found anything before Sep 2002?

I suppose he meant GDC 0.19 which is based on the DMD 0.162 frontend.

-- 
Lars Ivar Igesund
blog at http://larsivi.net
DSource & #D: larsivi

Lars Ivar Igesund wrote:
> 
> I suppose he meant GDC 0.19 which is based on the DMD 0.162 frontend.
> 

	Yes, you are correct.  I wasn't all that clear about which part I was
talking about.

	Thanks for the info folks,
		Anton

On 2006-08-10 16:31:45 -0700, Anton V Staaf <dm@socialhacker.com> said:
> 
> import std.stdio;
> 
> void main ()
> {
>     static int[int]	init;
>     int[int][int]	array;
> 
>     array[12] = init;
> 
>     array[12][15]++;
> }

The fact that you are using ++ makes this code invalid even if the symptom you state is there.  (++ is a lookup and an increment.)

However, I think you are correct about the multidimensional problem anyways as I have run into it in the past.

I think you have to do:

array[12] = new int[int];
array[12][15] = 1;

for the time be-ing

-S