Re: Template : cannot convert parameter 1 from const * to *const & ?

From:
"Victor Bazarov" <v.Abazarov@comAcast.net>
Newsgroups:
comp.lang.c++
Date:
Wed, 23 May 2007 10:59:31 -0400
Message-ID:
<f31ksk$nma$1@news.datemas.de>
nassim.bouayad.agha@gmail.com wrote:

Hello,
here is a code snippet showning my problem :


The first problem is all those underscores. Why do you think
you need them at all?

template<typename _K>
class TClass1
{
public:
void Process(const _K& arg) const
{

}
};
template<typename _I>
class TClass2
{
public:
void Process(const _I* & arg) const
{
_class1.Process(arg);


'_I' is 'int', right? '_class1' then 'TClass1<int*>', right?
Then its template argument (the '_K' inside) is 'int*', right?
What's the specification of the 'Process' member, then?

    void TClass1<int*>::Process(int* const&);

So, when you're calling '_class1.Process', what argument type
are you giving? '_I const * &'. Considering '_I' is 'int',
you are trying to call 'Process' with

   int const * &

instead of

   int * const &

.. Decide on the position of the const. Or drop the * from
the definition of '_class1'.

}
protected:
TClass1<_I*> _class1;

};
int main(int argc, char* argv[])
{

TClass2<int> test1;

int* ptr = new int;

test1.Process(ptr);

delete ptr;

return 0;
}

This code does not compile, I have got the following error message :
"cannot convert parameter 1 from 'const int *' to 'int *const & '"
Any idea?I have noted that if I declare _class1 as TClass1<const _I*>,
it is working...


Right. If you add a const at the _I, the function you're trying to
call is

    void TClass1<int const*>::Process(int const* const&);

which is fine. Its argument ('int const* const&') is compatible with
'int const* &' you're trying to give it.

V
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