Function template

 

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Description

Templates allow generic function design that work on various types, without the need of rewriting it multiple times

Syntax

Declaration

template < template_arguments > function_declaration	(1)
export template < template_arguments > function_declaration	(2)	(until C++11)

1. Template function declaration
2. Exported template function declaration. The function body can be defined in a separate file

Arguments

class identifier	(1)
typename identifier	(2)
integral_type identifier	(3)
class identifier = type_name	(4)	(since C++11)
typename identifier = type_name	(5)	(since C++11)
integral_type identifier = const_expr	(6)	(since C++11)

1-2) Inside the function identifier can be used as a type

3) Inside the function identifier can be used as a constant

4-6) Default arguments

Specialization

template <> ret function_name < template_args > ( func_args ) body

Specialization changes the implementation of the template function for specific template parameters

Call

function_name < template_args > ( func_args )	(1)
function_name ( unambiguous_func_args )	(2)

1. Explicit template arguments, if func_args don't match perfectly with the types as in the template declaration (with the given template_args) the usual casting will occur
2. Implicit template arguments, deduced from the function arguments. No ambiguity can be present

Example

template<typename T>
struct S {
    template<typename U> void foo(){}
};
 
template<typename T>
void bar()
{
    S<T>s;
    s.foo<T>(); // error: < parsed as less than operator
    s.template foo<T>(); // OK
}

See Also

• class template
• function declaration
• template
• typename