Re: Template typedefs
On Sep 12, 3:28 am, alexandro...@meta.ua wrote:
As we know, using template typedefs is illegal in C++:
template <typename T>
typedef std::vector<T> Vector; // won't compile
It is suggested, that the following workaround can be used to
implement "template typedefs":
template <typename T>
struct Types
{
typedef std::vector<T> Vector;
};
...
Types<int>::Vector numbers;
However, this prevents some argument deduction scenarios when calling
a templated function. The following example compiles on MSVC 9.0:
//----------------------------------------------------------
#include <vector>
template <typename T>
void signify( const std::vector<T>& )
{
}
int main()
{
std::vector<int> v;
signify( v );
return 0;
}
//----------------------------------------------------------
Whereas the following doesn't:
//----------------------------------------------------------
#include <vector>
template <typename T>
struct Types
{
typedef std::vector< T > Vector;
};
template <typename T>
void signify( const typename Types< T > :: Vector& )
{
}
int main()
{
Types< int > :: Vector v;
signify( v );
return 0;
}
//----------------------------------------------------------
The error concerns "signify( v );" line and is reported to be : "
could not deduce template argument for 'T' "
Is there a workaround to make argument deduction function with
templated typedefs?
I ran your code through Comeau online, and I think the error may be
because vector actually has *2* template parameters, one of which is
defaulted.
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