Re: Conversion Operator in Template Class

From:
James Kanze <james.kanze@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Thu, 19 Mar 2009 01:53:41 -0700 (PDT)
Message-ID:
<e7209f52-8d94-4127-b955-bb91473f40b8@33g2000yqm.googlegroups.com>
On Mar 18, 4:12 pm, joec...@gmail.com wrote:

Hmm... Why doesn't this work and use the conversion operator?
(It doesn't compile)

template<typename T>
class Foo
{
};

template<typename T>
  void bar(Foo<T>& a){}

template<typename T>
class Goo
{
public:
  operator Foo<U>(){return m_foo;}


What's U?

 Foo<U> m_foo;


Same question?

};

int main()
{
Goo<float> g;
 bar(g); // why doesn't this convert to Foo<U> ??
}


Your class template Goo shouldn't compile, since there is no
symbol U defined anywhere. If you replace the U with T, it
still won't compile, because the compiler doesn't know which
specialization of bar to use, and it can't do overload
resolution before bar has been specialized.

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James Kanze (GABI Software) email:james.kanze@gmail.com
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