[Bug libstdc++/5583] std::set::iterator is readonly

["erikhaugen at yahoo dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From erikhaugen at yahoo dot com  2003-11-26 00:13 -------
(In reply to comment #5)
> State-Changed-From-To: feedback->closed
> State-Changed-Why: LWG Defect Report #103 has resulted in a change to the C++
>     Standard:  std::set::iterator is /required/ to be read-only.
>     So, this is now definitely not a bug.  :-)
>     
>     Your example of directed edges doesn't really work:  you
>     didn't specify how "edge_t" is supposed to be ordered, but
>     assuming that you define an operator< which examines the
>     'weight' member, then you /still/ can't change the weight,
>     because that would be changing the ordering!  It's right
>     back to the original problem...

No, the example actually does work just fine.  The missing operator< should 
only compare u and v.  The poster made this very clear: "Obviously edges of a 
directed weighted exclusively are distinguished by their vertices. Obviously it 
would be nonsense to allow edgessets like {(1,2,3),(1,2,3)} or {(1,2,3),
(1,2,inf)}."  Your assumption that operator< would examine the weight is 
certainly incorrect.

This is a fine example of why you would want to be able to modify a value in a 
set, but I guess as of the defect report you'll have to pick a different data 
structure.

-Erik Haugen <erikhaugen@yahoo.com>

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=5583