Re: Class template specialization with template parameter

Greg Herlihy <>
Wed, 14 May 2008 13:20:24 -0700 (PDT)
On May 14, 12:51 pm, flopbucket <> wrote:


First, thanks for the reply.

Foo<int> uses the normal template, but Foo<std::map<T1, T2> > for any
types of T1 and T2 uses the specifalization?

Not sure what you're asking here.

What I was trying to say was that if I declare:

Foo<int> myFoo();

I believe that you mean to declare an object (and not a function):

   Foo<int> myFoo;

The instantiation will be for the normal/not-specialized template.


But if I declare:

Foo<std::map<int, std::string> > myFoo2();

Again, I believe that you want:

   Foo<std::map<int, std::string> > myFoo2;

it will use the specialization... and that regardless of the types
used for std::map (in this case, int and std::string), any
"Foo<std::map<typeA, typeB> > myFooExample()" will always
instantiate the specialization.

The answer depends on how many template parameters "std::map"
requires. The usual number is two - the two specified by the C++
Standard. An implementation however is allowed to require additional
temmplate type parameters for a std::map. So, assuming that std::map
requires only two type parameters, then the answer is "yes".


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