Introduction to C++ STL Iterators
Introduction to C++ STL Iterators
C++ Standard Template Library (STL) iterators are one of the most powerful and useful features of the C++ language. They provide a way for developers to manipulate data in a generic manner, without having to write the same code over and over again. The vast majority of STL containers (including vectors, list, associative containers, deque, etc.) provide support for iterators, enabling easy manipulation of their elements.
What is an Iterator?
An iterator is an object that enables you to traverse a container. In other words, an iterator lets you move around within a specific container to access and modify its elements. Depending on the type of iterator, you might be able to access elements in both the forward and backward directions.
It's important to note that an iterator does not guarantee any particular order when browsing through a container; when using an iterator, the only guarantees you get are the ability to traverse a container and the fact that you will eventually come back to your original position (if no other elements were added or removed from the container). It's up to the programmer to decide how to use the iterator.
Types of Iterators
There are several types of iterators available in STL. The most common ones are input iterators, output iterators, forward iterators, bidirectional iterators, and random-access iterators.
Input iterators allow you to traverse through a container sequentially in a forward direction. Output iterators let you write values to a container, but you can't read from it. Forward iterators enable you to traverse a container in both the forward and backward directions. Bidirectional iterators allow you to traverse a container in both the forward and backward directions. Finally, random-access iterators allow you to traverse a container randomly in any direction you want.
Using Iterators
Once you know what type of iterator you need, you can start writing code to take advantage of their power. For example, if you want to iterate over a vector of integers, you would use a forward iterator, like this:
vector v;
forward_iterator it;
for(it = v.begin(); it != v.end(); ++it)
{
// Do something with the element pointed by the iterator
}
As you can see, using the forward iterator allows us to easily loop through all elements of the vector without having to write any extra code. We can simply call begin() and end() to get the first and last elements, then increment the iterator until we reach the end.
Conclusion
C++ Standard Template Library iterators are an incredibly useful and powerful feature of the C++ language. By learning how to use them effectively, developers can write much cleaner, simpler, and more efficient code. Iterators can be used with almost any STL container, making them an invaluable tool for manipulating data.