views:

90

answers:

2

A constructor of a class can be a template function. At the point where such a constructor is called, the compiler usually looks at the arguments given to the constructor and determines the used template parameters from them. Is there also some syntax to specify the template parameters explicitly?

A contrived example:

struct A {
   template<typename T>
   A() {}
};

Is there a way to instantiate this class? What is the syntax to explicitly specify the constructor's template parameters?

My use case would be a problem were the compiler doesn't seem to find the correct templated constructor. Explicitly specifying the template parameters would probably generate more useful error messages or even resolve the problem.

A: 
Noah Roberts
I don't quite understand the answer... how is it related to the question?
David Rodríguez - dribeas
It shows how you can do it. It just so happens that you can't do it the way the question asked.
MSN
Too bad comments can't be demoted. That one is far from "great".
Noah Roberts
You can also do it in a way so that the ctor doesn't appear to need args: `template <typename T> A(const T* = NULL);` Be sure to keep that space between * and = or you'll wonder for days what the error message means...
dash-tom-bang
I don't suppose the person who up-voted that actually tried it. You can't do that because the compiler is unable to figure out what T is meant to be without the argument.
Noah Roberts
+8  A: 

No. The C++03 standard says:

[Note: because the explicit template argument list follows the function template name, and because conversion member function templates and constructor member function templates are called without using a function name, there is no way to provide an explicit template argument list for these function templates.] (§14.5.2/5)

James McNellis