Re: Problem with overloading operator *, I think

Hello group! I tried to make a simple program to exhibit why making a
operator() in a functor a member template is a good idea, but I can't
get this code to compile, hehe. I've reduced it to the following
complete test program:

#include <algorithm>
#include <iostream>
#include <vector>

using namespace std;

template <typename T>
class Foo
{
public:
  explicit Foo(const T& v) : m_v(v) {}

  bool operator==(const Foo& rhs) // Should I actually write const
Foo<T>& rhs here, btw?
  {
     return m_v == rhs.m_v;
  }

  Foo operator*(const int val)

  {
     T v = m_v * val;

     return Foo(v);
  }

private:
  T m_v;
};

struct twice_over_functor
{
  template<typename T>
  bool operator()(const T& v1, const T& v2)
  {
     return (v2 == v1 * 2);
  }
};

typedef vector<Foo<int > >::const_iterator constitr;

int
main()
{
  vector<Foo<int> > v;
  int n;

  while (cin >> n)
  {
     v.push_back(Foo<int>(n));
  }

  constitr itr = adjacent_find(v.begin(), v.end(),
twice_over_functor());

  if (itr != v.end())
  {
     cout << "Pair found!" << endl;
  }
  else
  {
     cout << "No pairs found!" << endl;
  }
}

The error I get when compiling is:
$ g++ -Wall -Wextra -std=c++98 -pedantic -g copy.cpp -o runme
copy.cpp: In member function `bool twice_over_functor::operator()
(const T&, const T&) [with T = Foo<int>]':
/usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/bits/stl_algo.h:395:
instantiated from `_ForwardIterator
std::adjacent_find(_ForwardIterator, _Forwa
rdIterator, _BinaryPredicate) [with _ForwardIterator =
__gnu_cxx::__normal_iterator<Foo<int>*, std::vector<Foo<int>,
std::allocator<Foo<int> > > >,
_BinaryPredicate = twice_over_functor]'
copy.cpp:51: instantiated from here
copy.cpp:34: error: no match for 'operator*' in 'v1 * 2'
copy.cpp:19: note: candidates are: Foo<T> Foo<T>::operator*(int) [with
T = int] <near match>

Where am I going wrong?