Template Function

Template allow us to write functions or class once but get a whole family of overload specifications:

template< typename T >
void fun(const T& input) { ... }

void fun(const int& input) { ... }
void fun(const float& input) { ... }
void fun(const char& input) { ... }
void fun(const MyClass& input) { ... }

Recall: two functions are overloaded if they have the same name and return type, but have different parameter types.

When to use?

When you find yourself writing functions with essentially the same body, but for different types.
Repetitive code is a sign of bad design because if a correction or modification for one of the functions also has to made for any other we've made.

Example

template< typename T>
int sum_every_other(const T& ls) {
	int total = 0;
	for (typename T::const_iterator it = ls.cbegin(); it != ls.cend(); ++it) {
		total += *it;
		if (++it == ls.cend()) break;
	}
}

• If we pass std::vector<int>appropriately function overload.
• When we need to use a nested class (like in this format: ::const_iterator) in the template, then you need to tell the compiler that it really is the type by using type name here.