Ivor Horton's Beginning Visual C++ 2012

ALGORITHMS

Algorithms are STL function templates that operate on a set of objects provided to them by an iterator. Because the objects are supplied by an iterator, an algorithm needs no knowledge of the source of the objects to be processed. The objects could be retrieved by the iterator from a container or even from a stream. Because iterators work like pointers, all STL template functions that accept an iterator as an argument will work equally well with a regular pointer.

As you’ll see, you will frequently use containers, iterators, and algorithms in concert, in the manner illustrated in Figure 10-1.

FIGURE 10-1

When you apply an algorithm to the contents of a container, you supply iterators that point to objects within the container. The algorithm uses these iterators to access objects within the container and to write them back when appropriate. For example, when you apply the sort() algorithm to a vector, you pass two iterators to the sort() function. One points to the first element, and the other to one past the last element. The sort() function uses these iterators to access objects for comparison, and to write the objects back to the container to establish the ordering. You see this working in an example later in this chapter.

Algorithms are defined in two standard header files, the algorithm header and the numeric header.