I have the following C++ code:
template <class T1, class T2, class T3>
void MetaTypeHandler(T1 lambda1, T2 lambda2, T3 lambda3) {
lambda1(1);
lambda2('x');
lambda3(true);
}
int main() {
auto f = [] (auto x) {};
MetaTypeHandler(f,f,f);
}
Passing f multiple times is ugly. Is it possible to write MetaTypeHandler() so that f is passed only 1 or 2 times? I think that template template parameters may help, but can't wrap my head around them.
I don't understand the problem.
It's a generic lambda.
Substantially the object of a struct with a template operator() in it.
So you can pass it one time only and use it with all types you want
#include <iostream>
template <typename T>
void MetaTypeHandler (T lambda)
{
lambda(42);
lambda('x');
lambda("abc");
lambda(true);
}
int main()
{
MetaTypeHandler(
[](auto const & x){ std::cout << "x is " << x << std::endl;});
}
You can just provide an overload:
#include <iostream>
template <class T1, class T2, class T3>
void MetaTypeHandler(T1 lambda1, T2 lambda2, T3 lambda3) {
lambda1(1);
lambda2('x');
lambda3(true);
}
template <class T>
void MetaTypeHandler(T lambda)
{
MetaTypeHandler(lambda, lambda, lambda);
}
int main() {
auto f = [] (auto x) {std::cout << x << std::endl;};
MetaTypeHandler(f);
}
So you can pass 3 different handlers, or one handler executing 3 times.
