In page 668 of Stroustrup's book (4th edition - first printing) you`ll find the following example of a template class?

template<typename C>
class String{
public:
String();
...
private:
int sz;
C* ptr;
};


In page 679 the author writes:

Members of a template class are themselves templates parameterized by
the parameters of their template class. When such a member is defined
outside its class, it must explicitly be declared as template. For
example:

template<typename C>
String<C>::String()
:sz(0), ptr(ch)
{
ch[0] = {};
}


There is an obvious error in this example. The variable ch doesn't make any sense above. But that has nothing to do with my question. What I'd like to know is why the constructor above can't be defined without the parameter C, as shown below?

ch

C

template<typename C>
String::String()
: sz(0), ptr(nullptr)
{
}


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