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The Standard Template Library

Chapter 16

Announcement

No class on Friday, Feb. 18

Engineering Expo

Participate!

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Objectives

You will be able to use the Standard Template Library list class in C++ programs.

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C++ Templates

We often need essentially identical classes for use with different kinds of objects.

Examples: Lists Stacks Queues

Compare to arrays

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C++ Templates

The C++ template permits us to define classes with blanks to be filled in with specific class names at compile time. Called the template parameter. A template can have multiple parameters.

The template class cannot be instantiated directly.

It is a pattern from which classes can be created.

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C++ Templates

Specifying the parameter configures the template as a real class definition. Filling in the blanks.

When we declare an object of a template class and supply its parameters, the compiler creates a real class.

A template with parameters can be used like a normal class.

Compare to #define.

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C++ Templates

You can define templates in a C++ program just as you can define normal classes. Not the subject of this presentation. We will only be using an existing template.

There is a large library of predefined templates available with any C++ compiler. The C++ Standard Template Library

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The Standard Template Library

Big Subject Brief introduction today.

We will use one template as an example:

The list template

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STL Components

Containers: Generic "off-the-shelf" class templates for

storing collections of data

Algorithms: Generic "off-the-shelf" function templates

for operating on containers

Iterators: Generalized pointers that allow

algorithms to operate on almost any container

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The Ten STL Containers

Sequential: deque, list, vector

Associative: map, multimap,

multiset, set

Adapters: priority_queue,

queue, stack

All STL containers use copy semantics.

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The List Template

The STL list template is a generic linked list class.

We can use it to create a list of objects of any type: ints doubles Circles Dogs Cats

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Frequently Used Methods

size() Returns number of elements empty() True if list is empty front() Returns first item back() Returns last item push_back() Add item to end of list pop_back() Remove item from end of list push_front() Add item to beginning of list pop_front() Remove item from beginning of list sort() Sort using < operator

Many more!

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Example

Create a new project, List_Demo Add main.cpp

#include <iostream>

using namespace std;

int main(void)

{

cout << "This is List_Demo\n";

cout << "Normal termination\n";

cin.get();

cin.get();

return 0;

}

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Program Running

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Using the list template

#include <list>

...

list<int> int_list;

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Using the list Template

Add to main():#include <list>

...

list<int> int_list;

for (int i = 1; i <6 ; ++i)

{

cout << "Adding " << i << " to end of list\n";

int_list.push_back(i);

}

cout << "Here is the list:\n";

while (!int_list.empty())

{

int next_item = int_list.front();

cout << next_item << endl;

int_list.pop_front();

}

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Program Running

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Random Numbers

#include <iostream>

#include <list>

#include <cstdlib>

using namespace std;

int main(void)

{

list<int> int_list;

cout << "This is List_Demo\n";

for (int i = 1; i <6 ; ++i)

{

int val = rand() % 100;

cout << "Adding " << val << " to end of list\n";

int_list.push_back(val);

}

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Program Running

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Sorting the List

int main(void)

{

list<int> int_list;

cout << "This is List_Demo\n";

for (int i = 1; i <6 ; ++i)

{

int val = rand() % 100;

cout << "Adding " << val << " to end of list\n";

int_list.push_back(val);

}

cout << "Sorting the list\n";

int_list.sort();

cout << "Here is the list:\n";

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Program Running

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Sorting into Descending Order

bool greater_than(int lhs, int rhs)

{

return lhs > rhs;

}

int main(void)

{

...

cout << "Sorting the list into descending order\n";

int_list.sort(greater_than);

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Program Running

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Iterators

The STL defines iterators as generalized pointers that permit user to iterate over all elements in a container.

Permits the same code to be used with various kinds of containers.

Use like a pointer.

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Using a Iterator

cout << "Iterating over the list\n";

list<int>::iterator i;

i = int_list.begin();

while (i != int_list.end())

{

int next_item = *i;

cout << next_item << endl;

++i;

}

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Program Running

End of Presentation