I was doing an experiment, code below:

template<typename T>
struct S
{
	explicit S(T v) :val{ v } {};
	T val;
};

int main()
{
	S<int> MyS('g');
	cout << MyS.val << endl;//Output is 103

	return 0;
}

Even though I am providing T with a type which is int, and I have an explicit constructor, why I have an implicit conversion from char to int? Shouldn't it see that T is int since I'm telling it so and thus give me error for constructing an S out of char?

Thanks @Kylotan, I had grossly misunderstood the meaning of that keyword

I'm changing the title of the topic into "Questions about Templates" because I'm experimenting with it and I know I will have more than one, doesn't seems right to make 1000 mini-topics

So now I have the code below:

template<typename T>
struct S
{
	S(T v) :val{ v } {};
	T val;
};

template <typename R, typename T>
R& get(T& e)
{
	return e.val;
}

int main()
{
	S<char> MySChar('B');
	cout << "MySChar: " << MySChar.val << endl;
	
	cout << "Returned val: " << get<char>(MySChar) << endl;

	return 0;
}

The function get is not part of the S class, as required from the book exercise (which is "" Add a function template get() that returns a reference to val.")

I don't like that I have to specify the return type when I call it, if I have 5 different instantiation of S it becomes messy, so I was trying to make it in such a way that I can just write get(MySChar) and it just works with wathever instantiation of S, but I am failing on it, code below:

template<typename T>
struct S
{
	S(T v) :val{ v } {};
	T val;
	typedef T type;
};

template <typename T, typename R>
R& get(T& e)
{
	using R = e.type;
	return e.val;
}

int main()
{
	S<char> MySChar('B');

	cout << "MySChar: " << MySChar.val << endl;

	cout << "Returned val: " << get(MySChar) << endl;

	return 0;
}

How would I do that the proper way?

Well, I kind of found a solution to my last question (by throwing everything at random at it), which is auto& return type. But still out of curiosity, what would be the second best alternative to auto, using templates?

template <typename T>
auto& get(T& e)
{
	return e.val;
}

15 minutes ago, Kylotan said:

but this is all too abstract for me to even work out what you're trying to do at a glance.

nothing too fancy, I'm just trying to make the code below compile without changing it but just by modifying that get() function 

The code below the commented line that says "//THIS 5 LINES BELOW NEEDS TO COMPILE"

int main()
{
	S<int> MySInt(5);
	S<char> MySChar('B');
	S<double> MySDouble(2.2);
	S<string> MySString(string("wow!"));
	S<vector<int>> MySVec(vector<int>(4, 99));

	cout << "MySInt: " << MySInt.val << endl;
	cout << "MySChar: " << MySChar.val << endl;
	cout << "MySDouble: " << MySDouble.val << endl;
	cout << "MySString: " << MySString.val << endl;

	cout << "MySVec: ";
	for (auto& e : MySVec.val)
		cout << e << " ";
	cout << endl;

	//THIS 5 LINES BELOW NEEDS TO COMPILE
	cout << "Returned val from get(): " << get(MySInt) << endl;
	cout << "Returned val from get(): " << get(MySChar) << endl;
	cout << "Returned val from get(): " << get(MySDouble) << endl;
	cout << "Returned val from get(): " << get(MySString) << endl;
	cout << "Returned val from get(): " << get(MySVec)[0] << endl;

	return 0;
}

So this is the function with decltype (assuming I am using it correctly) but doesn't work as well

template <typename T, typename R>
R& get(T& e)
{
	decltype(e.val) R;
	return e.val;
}

auto& as return type works just fine and those 5 lines compile, I was just wondering if there where any other ways  

Moving to a new question, why is the code below not compiling if I uncomment one of the 4 commented-out lines ?

Function "set(Container, newValue, ID)"  takes a "MyContainer" class, a new value to set and an optional ID, just in case is a MyContainer<vector<int>>.

inside of it, takes the "val" of the MyContainer which returns wathever it is containing, in the example case is indeed a vector<int>&, but as soon as I try to use an operator<< or operator= on Vec, this thing doesn't compile...what am I not getting here?

template<typename T>
struct is_Container {
	static const bool value = false;
};

template<typename T, typename Alloc>
struct is_Container<vector<T,Alloc>> {
	static const bool value = true;
};

template <typename T, typename V>
void set(MyContainer<T>& e, V newVal, int ID = 0)
{
	T& Val = e.get();
	if (is_Container<T>::value)
	{
		cout << "is a vector" << endl;
		//cout << Val[ID] << endl;
		//Val[ID] = newVal;
	}
	else
	{
		cout << "is not a container" << endl;
		//cout << Val << endl;
		//Val = newVal;
	}
}