For the following type system,
<code>template <typename U, typename V>
struct Base { ... };
struct Derived1 : Base<TypeA, TypeB> { ... };
struct Derived2 : Base<TypeA, TypeC> { ... };
</code>
<code>template <typename U, typename V>
struct Base { ... };
struct Derived1 : Base<TypeA, TypeB> { ... };
struct Derived2 : Base<TypeA, TypeC> { ... };
</code>
template <typename U, typename V>
struct Base { ... };
struct Derived1 : Base<TypeA, TypeB> { ... };
struct Derived2 : Base<TypeA, TypeC> { ... };
I would like to be able to write functions that accept parameters that have been derived from Base while restricting some (none, all) of the template parameters in Base. My idea is to use C++ concepts for this (though I’m open for other approaches!). Essentially, I am looking for something like
<code>template <typename T, typename U, typename V>
concept FromBase = requires ...
</code>
<code>template <typename T, typename U, typename V>
concept FromBase = requires ...
</code>
template <typename T, typename U, typename V>
concept FromBase = requires ...
such that I can write functions like this
<code>void foo(FromBase auto param); // accepts anything derived from `Base`
void bar(FromBase<TypeA> auto param); // accepts `Derived1` and `Derived2`
void baz(FromBase<TypeA, TypeB> auto param); // accepts `Derived1`, but not `Derived2`
</code>
<code>void foo(FromBase auto param); // accepts anything derived from `Base`
void bar(FromBase<TypeA> auto param); // accepts `Derived1` and `Derived2`
void baz(FromBase<TypeA, TypeB> auto param); // accepts `Derived1`, but not `Derived2`
</code>
void foo(FromBase auto param); // accepts anything derived from `Base`
void bar(FromBase<TypeA> auto param); // accepts `Derived1` and `Derived2`
void baz(FromBase<TypeA, TypeB> auto param); // accepts `Derived1`, but not `Derived2`
How would I do this with concepts? Or is this even possible with C++? Note that I’m specifically looking for a solution that is “easy on the eyes and mind”, i.e., ideally I don’t want to use N different concepts to support N potential parameters.
Bonus question: Is this also possible with mixed type/non-type template parameters in Base?