• bearophile (25/25) Nov 06 2012 import std.stdio;
• H. S. Teoh (23/32) Nov 06 2012 [...]
• Don Clugston (10/40) Nov 07 2012 I keep getting hurt by the bizarre "magic null" that happens with AAs.
• kenji hara (5/9) Nov 07 2012 If you tell me which bugs should be fixed for the new AA

"bearophile" <bearophileHUGS lycos.com> writes:

import std.stdio;
void main() {
     int[] a;
     int[int] aa;
     a ~= a.length;
     aa[10] = aa.length;
     writeln(a, " ", aa);
     a ~= a.length;
     aa[20] = aa.length;
     writeln(a, " ", aa);
}


It prints:

[0] [10:1]
[0, 1] [20:2, 10:1]

So the associative array is updated before taking its length. I 
suggest to try to fix this AA behavour before too much D2 code 
relies on this. I'd like to avoid this to become a permanent wart 
of D2.

My bug report is from February 2010, it's in the most important 
20 bug reports of mine. In my opinion it's wrong to add new 
features to D before similar bugs are fixed:

http://d.puremagic.com/issues/show_bug.cgi?id=3825

Thank you,
bye,
bearophile

"H. S. Teoh" <hsteoh quickfur.ath.cx> writes:

On Wed, Nov 07, 2012 at 05:08:43AM +0100, bearophile wrote:
[...]
 So the associative array is updated before taking its length. I
 suggest to try to fix this AA behavour before too much D2 code relies
 on this. I'd like to avoid this to become a permanent wart of D2.
 
 My bug report is from February 2010, it's in the most important 20
 bug reports of mine. In my opinion it's wrong to add new features to
 D before similar bugs are fixed:
 
 http://d.puremagic.com/issues/show_bug.cgi?id=3825

[...]

I'd love to fix AA's once for all. The problem is that right now the AA
code is scattered all over the compiler, and even within druntime it's a
schizophrenic mosaic of half-duplicated code, partly in aaA.d and partly
in object_.d. It's a major undertaking even just to refactor this code
in a sane way.

Would you like to help in this effort? ;-)

I tried to do it myself some time ago, and I did get as far as a struct
that works pretty much like the built-in AA's with quite a good number
of current issues fixed, but it got stuck with handling const, pure,
IFTI bugs, and a number of related issues.  Frankly, at this point I
believe that it's going to take more than one person to do it. We need a
team of about 2-3 to tackle different aspects of it so that we can clean
up the whole thing properly. My code is already up on github, but so far
it seems that no one has been interested to contribute yet.

I do agree that cleaning up AA's should be quite an important item in
D2. There are quite a lot of IMO serious problems with the current
implementation. But it ain't gonna happen unless more people help.


T

-- 
Meat: euphemism for dead animal. -- Flora

Don Clugston <dac nospam.com> writes:

On 07/11/12 05:38, H. S. Teoh wrote:
 On Wed, Nov 07, 2012 at 05:08:43AM +0100, bearophile wrote:
 [...]
 So the associative array is updated before taking its length. I
 suggest to try to fix this AA behavour before too much D2 code relies
 on this. I'd like to avoid this to become a permanent wart of D2.

 My bug report is from February 2010, it's in the most important 20
 bug reports of mine. In my opinion it's wrong to add new features to
 D before similar bugs are fixed:

 http://d.puremagic.com/issues/show_bug.cgi?id=3825

 [...]

 I'd love to fix AA's once for all. The problem is that right now the AA
 code is scattered all over the compiler, and even within druntime it's a
 schizophrenic mosaic of half-duplicated code, partly in aaA.d and partly
 in object_.d. It's a major undertaking even just to refactor this code
 in a sane way.

 Would you like to help in this effort? ;-)

 I tried to do it myself some time ago, and I did get as far as a struct
 that works pretty much like the built-in AA's with quite a good number
 of current issues fixed, but it got stuck with handling const, pure,
 IFTI bugs, and a number of related issues.  Frankly, at this point I
 believe that it's going to take more than one person to do it. We need a
 team of about 2-3 to tackle different aspects of it so that we can clean
 up the whole thing properly. My code is already up on github, but so far
 it seems that no one has been interested to contribute yet.

 I do agree that cleaning up AA's should be quite an important item in
 D2. There are quite a lot of IMO serious problems with the current
 implementation. But it ain't gonna happen unless more people help.


 T

I keep getting hurt by the bizarre "magic null" that happens with AAs. 
It makes the implementation really horrible.
Can we please please make it so that declaring an AA creates an empty 
AA? So that AAs are always reference types.
(It would also be OK if they had to explicitly created, just like 
classes are; but these semantics of "inserting an item into a null AA 
creates the AA first" is really awful).

Making AAs nicer and less bug-prone for users would make them easier to 
implement!

kenji hara <k.hara.pg gmail.com> writes:

2012/11/7 H. S. Teoh <hsteoh quickfur.ath.cx>:
[snip]
 I tried to do it myself some time ago, and I did get as far as a struct
 that works pretty much like the built-in AA's with quite a good number
 of current issues fixed, but it got stuck with handling const, pure,
 IFTI bugs, and a number of related issues.

If you tell me which bugs should be fixed for the new AA
implementation, I'll try to fix them.

Kenji Hara