Function Templates vs. Auto Keyword
The only thing which makes it the auto
keyword different from template
that is you cannot make a generic class using the auto
keyword.
class B { auto a; auto b; }
When you create an object of the above class it will give you an error.
B b; // Give you an error because compiler cannot decide type so it can not be assigned default value to properties
Whereas using template you can make a generic class like this:
template <class T>
class B {
T a;
};
void main() {
B<int> b; //No Error
}
Can the
auto
keyword in C++11 replace function templates and specializations?
No. There are proposals to use the keyword for this purpose, but it's not in C++11, and I think C++14 will only allow it for polymorphic lambdas, not function templates.
If yes, What are the advantages of using template functions and specializations over simply typing a function parameter as
auto
.
You might still want a named template parameter if you want to refer to the type; that would be more convenient than std::remove_reference<decltype(arg)>::type
or whatever.
In a nutshell, auto
cannot be used in an effort to omit the actual types of function arguments, so stick with function templates and/or overloads. auto
is legally used to automatically deduce the types of variables:
auto i=5;
Be very careful to understand the difference between the following, however:
auto x=...
auto &x=...
const auto &x=...
auto *px=...; // vs auto px=... (They are equivalent assuming what is being
// assigned can be deduced to an actual pointer.)
// etc...
It is also used for suffix return types:
template <typename T, typename U>
auto sum(const T &t, const U &u) -> decltype(t+u)
{
return t+u;
}