C++ In a Nutshell

Function Templates

A function template defines a pattern for any number of functions whose definitions depend on the template parameters. You can overload a function template with a non-template function or with other function templates. You can even have a function template and a non-template function with the same name and parameters.

Function templates are used throughout the standard library. The best-known function templates are the standard algorithms (such as copy, sort, and for_each).

Declare a function template using a template declaration header followed by a function declaration or definition. Default template arguments are not allowed in a function template declaration or definition. In the following example, round is a template declaration for a function that rounds a number of type T to N decimal places (see example 7-14 for the definition of round), and min is a template definition for a function that returns the minimum of two objects:

// Round off a floating-point value of type T to N digits.
template<unsigned N, typename T>  T round(T x);
// Return the minimum of a and b.
template<typename T> T min(T a, T b)
{ return a < b ? a : b; }

To use a function template, you must specify a template instance by providing arguments for each template parameter. You can do this explicitly, by listing arguments inside angle brackets:

long x = min<long>(10, 20);

However, it is more common to let the compiler deduce the template argument types from the types of the function arguments: ...