Std::istream& as function parameter - c++

Question

What is the best way to make a program that reads the elements from the input until the EOF and returns the container of read elements? This is what I have to do
p.h file:
#pragma once
#include <list>
#include <iostream>
typedef double Element;
template<typename T>
std::list<T> read(std::istream& u);
This is what I tried:
#pragma once
#include <list>
#include <iostream>
typedef double Element;
template<typename T>
std::list<T> read(std::istream& u){
while(u){
std::list<T> l;
l.push_front(u);
return l;
}
}
p.cpp file:
#include "p.h"
#include <iostream>
int main(){
double u;
std::cin>>u;
std::list<double> l=read(u);
}
What exactly do I have to pass as an argument the a main function? I tried passing an std::cin but it doesn't work. It could also be because read function is not defined properly.
Also I don't understand what's the point of typedef being double if we are making generic functions.

Answer 1

When you do l.push_front(u) you are trying to store the istream in the list. You need to read a T from the stream and store that instead. Also note that you need to declare l outside the loop in order to be able to read all values and then return l:
template<typename T>
std::list<T> read(std::istream& u){
T tmp;
std::list<T> l;
while(u >> tmp){
l.push_front(tmp);
}
return l;
}
Then specify the type you want to read from the stream by supplying it as a template parameter:
int main(){
auto l=read<double>(std::cin);
}