Re: Conversion Operator in Template Class

From:
Victor Bazarov <v.Abazarov@comAcast.net>
Newsgroups:
comp.lang.c++
Date:
Wed, 18 Mar 2009 13:54:08 -0400
Message-ID:
<gprcg0$sq8$1@news.datemas.de>
SG wrote:

On 18 Mrz., 16:27, Victor Bazarov <v.Abaza...@comAcast.net> wrote:

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

Because the Standard prohibits it. When deducing template arguments
from a function call, the conversions are not applied to the function
arguments.


In addition: The conversion would result in an rvalue which is not
allowed to bind to an lvalue reference to non-const.


In this particular test case, yes. But it's not going to be used even
if the conversion function is changed to

     operator Foo<U>& () { return m_foo; }

V
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