Re: std::tr1::unordered_set problem in GCC 4.1.2

Pete Becker <>
Sun, 8 Apr 2007 09:02:05 CST
Carl Barron wrote:

Martin M. Pedersen <> wrote:

struct TraxboardCompare
   bool operator()(const Traxboard& tb1, const Traxboard& tb2) const
     return (tb1.getHash()<tb2.getHash());

  tr1 unordered containers want an equal to comparision not a less than
one. This is one problem. further it is the objects themselves that
are compared for equality not the hashes. that is internally in
unorderd_* when objects have the same hash they are compared for
equality. The container already knoes that if the hashes are different
the objects are also.
   note your functor when actually called will always return false.

  You need an equal compare for,which you have so the default
std::equal_to should work.

It may well be that the semantics of the various functions aren't right,
but that doesn't mean that the interface is wrong. The code should compile.


    -- Pete
Roundhouse Consulting, Ltd. (
Author of "The Standard C++ Library Extensions: a Tutorial and
Reference." (

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