Comp 2673, Spring 2002

May 13, lecture notes



Reading Assignment:
    Chapter 12.1-12.4

Function templates - the purpose
    Imagine writing a function to sort an array of integers.  You'll have an
algorithm for reordering the list (such as bubble sort, or quicksort),
and some line (or lines) of code will compare two integers to see if they're
in the correct order.  Now imagine writing a function to sort an array of
dates.  The entire block of code is the same, except for the line (or lines)
that compare two dates to see if they're in the correct order.  What a drag
to have two functions that are so very similar - we are duplicating a lot
of code.  The solution to this problem is function templates, which allow
us to create a range of related functions all at once.  A function template
is a blueprint for a function, allowing for software re-use.
    Function templates are an extension of overloaded function.  If you want
to make overloaded functions that do EXACTLY the same thing, just on different
variable types, then function templates are the way to go. 

Example - function that prints the contents of an array
The first line:
template <class T>
says that this function is actually a function template,
with a parameters of varying type that we'll call T.  "class T" means that
the caller can use this function with any user-defined or built-in type.
We'll call this function with three different built-in types, then a
user-defined type.  The compiler automatically generates 4 overloaded
functions for us.
functemp.cpp