Template Function Specialization - c++

Question

I am doing an exercise on templates and I am now dealing with specializations. I have defined a function T read_val(T& v) that takes input from cin and compiles the T val inside my template<typename T> struct S. I wish to specialize this function to types int, double, char, string but, when I am trying to do it, I'm keep getting errors. Here is what I wrote:
Header.h:
#ifndef Templates_Header_h
#define Templates_Header_h
#include <iostream>
using namespace std;
template<typename T>
struct S
{
private:
T val;
public:
S() : val{} {};
T* get();
T* get() const;
T set();
T operator=(const T&);
T read_val(T& v);
void print_val() const;
};
template<typename T>
void S<T>::print_val() const
{
cout << "Value is: " << val << endl;
}
template<typename T>
T* S<T>::get()
{
T* p = &val;
return p;
}
template<typename T>
T S<T>::set()
{
T newvalue;
cout << "Type new value: ";
cin >> newvalue;
S<T>::val = newvalue;
return S<T>::val;
}
template<typename T>
T S<T>::operator=(const T&)
{
T val1;
val1 = val;
return *this;
}
template<typename T>
T* S<T>::get() const
{
T* p = &val;
return p;
}
template<typename T>
T S<T>::read_val(T &v)
{
cout << "Type Value: ";
cin >> v;
return S<T>::val = v;
}
#endif
Header.cpp
#include <stdio.h>
#include "Header.h"
#include "std_lib_facilities.h"
template <>
struct S <int> // Specialization
{
private:
int val;
public:
S() : val{0} {};
};
template<>
struct S<char> // Specialization
{
private:
char val;
public:
S() : val{'0'} {};
};
template <>
struct S<double> // Specialization
{
private:
double val;
public:
S() : val{0.0} {};
};
template <>
struct S<string> // Specialization
{
private:
string val;
public:
S() : val{""} {};
};
template<>
struct S<vector<int>> // Specialization
{
private:
vector<int> val;
public:
S() : val{0} {};
};
template<> // !! ERROR !!
int read_val(int& v)
{
cout << "Type a value: ";
cin >> v;
return v;
}
Xcode is reporting "No function template matches function template specialization 'read_val'". I was surfing the net reading examples and references but I cannot solve it. Can you help me? I need an example to fix it in mind.
Thanks!

Answer 1

There should be no CPP file for a template header. Your implementation is already in the header file!
Create main.cpp with:
#include "Header.h"
#include <iostream>
int main()
{
S<int> my_S;
int val;
my_S.read_val(val/*by ref*/);
std::cout << "The read value is " << val << std::endl;
return 0;
}
Or something like that, I didn't compile it...
According to your implementation I see that you missed the point of templates. You need to define it only once (no need to rewrite it manually for each type like int, float, etc., the compiler will do it for you).