16.2.11 Default template arguments

A later refinement to C++ templates was the concept of default template arguments. Templates allow C++ types to be parameterized and as such, the parameter is in essence a variable that the programmer must specify when instantiating the template. This refinement allows defaults to be specified for the template parameters.

This feature is used extensively throughout the Standard Template Library (see section 16.2.13 Standard Template Library) to relieve the programmer from having to specify a comparison function for sorted container classes. In most circumstances, the default less-than operator for the type in question is sufficient.

If your compiler does not support default template arguments, you may have to suffer without them and require that users of your class and function templates provide the default parameters themselves. Depending on how inconvenient this is, you might begrudgingly seek some assistance from the C preprocessor and define some preprocessor macros.