I'm currently learning how templates work in C++. In particular, I'm looking at the single member function templates within class templates. To understand what I mean, code is found below.
// foo.h
template<typename A>
class foo {
template<typename B>
void boo(B);
};
// foo.cpp
template<typename A>
void foo<A>::boo(B value) {} // compiler error: 'Unknown' type name B
// or if I try this
template<typename B>
void foo<A>::boo(B value) {} // compiler error: Use of undeclared identifier A
I'm trying to use two typenames, one from the class template, and one from the single file template, for that specific function. But in those two versions above, I get compiler errors. How would I bypass this problem?
Both the two sets of template parameters are required to define the member template.
(emphasis mine)
If the enclosing class declaration is, in turn, a class template, when a member template is defined outside of the class body, it takes two sets of template parameters: one for the enclosing class, and another one for itself:
E.g.
template<typename A>
template<typename B>
void foo<A>::boo(B value) {}
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