CODEWITHSUNDEEP
c++templatescompiler-errorstemplate-specialization
jrd1
jrd1

Reputation: 10716

Defining and calling a C++ function of a specialized template

I am currently learning C++ in-depth, and I have come across something that has stumped for a couple hours now. Why is it when I make a template and then specialize it, that I can't call or define that function for the specialized version? The compiler complains, and I have scoured Google for a possible hint as to what I am doing wrong, but to no avail. I am very sure it is something very simple that I am overlooking:

template <typename T>
class C { };

//specialization to type char
template <>
class C <char> 
{
  public:
    void echo();
};

//compiler complains here
template <>
void C <char> :: echo() 
{
  cout << "HERE" << endl;
}

error: template-id ‘echo<>’ for ‘void C::echo()’ does not match any template declaration

Demo.

Upvotes: 5

Views: 1317

Answers (2)

Robᵩ
Robᵩ

Reputation: 168626

//specialization to type char
template <>
class C <char>
{
  public:
    void echo();
};

//template<>  <----- don't mention template<> here
void C <char> :: echo()
{
  cout << "HERE\n";
}

P.s. Never say endl when you mean '\n'. What is the C++ iostream endl fiasco?

Upvotes: 8

Hari
Hari

Reputation: 1803

Robᵩ's answer fixes the issue. It will be good to know more about the reason.

From Explicit (full) template specialization:

Members of specializations

When defining a member of an explicitly specialized class template outside the body of the class, the syntax template<> is not used, except if it's a member of an explicitly specialized member class template, which is specialized as a class template, because otherwise, the syntax would require such definition to begin with template required by the nested template.

Upvotes: 0

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