Re: msvc++ 2005 template question

From:
"Ben Voigt" <rbv@nospam.nospam>
Newsgroups:
microsoft.public.vc.language
Date:
Wed, 18 Oct 2006 12:29:52 -0500
Message-ID:
<OoGlGst8GHA.3384@TK2MSFTNGP05.phx.gbl>

     typedef typename EOT::Fitness Fitness;

This is actually the only time "typename" isn't used, because typedef
requires a typename anyway.

The place typename is needed is undoubtedly in this code:

  struct GetFitness { Fitness operator()(const EOT& _eo) const { return
_eo.fitness(); } };

  /** returns the fitness of the nth element */
 Fitness nth_element_fitness(int which) const
  { // probably not the fastest way to do this, but what the heck

      std::vector<Fitness> fitness(size());
      std::transform(begin(), end(), fitness.begin(), GetFitness());

      typename std::vector<Fitness>::iterator it = fitness.begin() +
which;
      std::nth_element(fitness.begin(), it, fitness.end(),
std::greater<Fitness>());
      return *it;
  }


I think the first line of that is the problem, and that because it's a
different type, where the typedef may not have been seen.

That whole line is a wtf?!?.
The only reason for a struct there would be for polymorphism through a
v-table.... but there's no inheritance and no v-table.
 It looks like it should read:
static Fitness GetFitness(const EOT& _eo) { return _eo.fitness(); }
But then, I haven't used std::transform. Try using "typename Fitness" on
that line.

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