Why Does Explicit Specialization of a Member Function Outside its Namespace Cause a C Compilation Error?

Explicit Specialization in Non-Namespace Scope

In template class CConstraint, an explicit specialization of the Verify member function for int is defined outside of the namespace of the class. This causes an error in g due to a violation of C standards.

According to C 03 §14.7.3/2, explicit specializations must be declared in the namespace of which the template is a member or, for member templates, in the namespace of which the enclosing class or enclosing class template is a member.

To resolve this issue, the explicit specialization of Verify for int must be declared within the namespace of CConstraint. This can be achieved by using the following modified code:

<br>template<typename T><br>class CConstraint<br>{<br>public:</p>
<pre class="brush:php;toolbar:false">CConstraint()
{
}

virtual ~CConstraint()
{
}

template <typename TL>
void Verify(int position, int constraints[])
{       
}

template <>
void Verify<int>(int position, int constraints[])
{   
}

};

Additionally, since explicit specializations of member functions require explicit specialization of the containing class, a better solution would be to move the Verify function out of the class and into a separate namespace:

<br>namespace detail<br>{</p>
<pre class="brush:php;toolbar:false">template <typename TL>
void Verify(int position, int constraints[]) { }

template <>
void Verify<int>(int position, int constraints[]) { }

}

template
class CConstraint
{

// ...

template <typename TL>
void Verify(int position, int constraints[])
{
    detail::Verify<TL>(position, constraints);
}

};

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