http://d.puremagic.com/issues/show_bug.cgi?id=10381

           Summary: Nonsense associative array comparison
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: wrong-code
          Severity: critical
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: verylonglogin.reg@gmail.com


--- Comment #0 from Denis Shelomovskij <verylonglogin.reg@gmail.com> 2013-06-16 18:29:05 MSD ---
Currently associative arrays are compared by comparing its `impl` pointers e.g.
`aa1 < aa2` is rewritten as `cast(void*) aa1 > cast(void*) aa2` instead of
calling a runtime function.

---
void main()
{
    int[int] aa1 = [0: 1];
    int[int] aa2 = [0: 1];
    assert(aa1 == aa2); // Passes
    assert(!(aa1 < aa2) && !(aa1 > aa2)); // Fails, different `impl`-s
}
---

And yes, there is not such function in druntime so this is druntime's issue too.

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--- Comment #1 from hsteoh@quickfur.ath.cx 2013-07-08 15:12:06 PDT ---
IMO, comparing AA's with < should be a compile-time error. AA's are unordered so it makes no sense to use < to compare them.

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bearophile_hugs@eml.cc changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bearophile_hugs@eml.cc


--- Comment #2 from bearophile_hugs@eml.cc 2013-07-08 15:58:43 PDT ---
(In reply to comment #1)
> IMO, comparing AA's with < should be a compile-time error. AA's are unordered so it makes no sense to use < to compare them.

There are some meaningful (and occasionally useful) operations done on whole associative arrays, like testing if the keys of an associative array are a subset (or strict subset) of the keys of another associative array. But probably it's not the best idea to use < to perform similar set comparisons...

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--- Comment #3 from Don <clugdbug@yahoo.com.au> 2013-09-19 23:20:27 PDT ---
https://github.com/D-Programming-Language/dmd/pull/2575

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Martin Nowak <code@dawg.eu> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |code@dawg.eu


--- Comment #4 from Martin Nowak <code@dawg.eu> 2013-09-20 12:42:36 PDT ---
(In reply to comment #2)
> There are some meaningful (and occasionally useful) operations done on whole associative arrays, like testing if the keys of an associative array are a subset (or strict subset) of the keys of another associative array.

Yes, interesting but too complex/specialized for built-in functionality IMHO.

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--- Comment #5 from hsteoh@quickfur.ath.cx 2013-09-20 13:31:02 PDT ---
(In reply to comment #4)
> (In reply to comment #2)
> > There are some meaningful (and occasionally useful) operations done on whole associative arrays, like testing if the keys of an associative array are a subset (or strict subset) of the keys of another associative array.
> 
> Yes, interesting but too complex/specialized for built-in functionality IMHO.

FWIW, using == on AA's already does (a superset of) what an AA subset operation
would do (iterate over AA keys and check for existence in the other AA).

But I agree that it shouldn't be built-in functionality. Maybe a nice library wrapper in std.array, but not much beyond that.

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--- Comment #6 from github-bugzilla@puremagic.com 2013-09-24 10:06:18 PDT ---
Commit pushed to master at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/f357fb07cfbb5b64c5a4ccc12a4ce7b83cb7a3b8 Fix issue 10381 Nonsense associative array comparison

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Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |bugzilla@digitalmars.com
         Resolution|                            |FIXED


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