Standard Template Library

The Standard Template Library forms the core of the Standards<ToolKit>.

Most C++ programs require the ability to use collections, such as arrays, lists, and sets. Until now, C++ programmers either had to write their own collection classes or purchase a proprietary commercial product. Non-standard commercial offerings have one or more of the following drawbacks.

Incompatibility among vendors-Because there was no standard for collection classes, every vendor's collection classes were incompatible. This caused difficulty in deciding how to return a collection of results from a function call, because multiple users of a function might be using collections from different vendors.
Use of virtual functions-Many collection hierarchies use inheritance and virtual functions, which tend to reduce performance. Although in many cases this is not a problem, many programmers do not want to use libraries unless they perform within a few percentage points of hand-coded C equivalents. Use of virtual functions also makes objects difficult to instantiate in shared memory.
Difficulty in adding new algorithms-Commercial vendors place their code for algorithms that work on collections within the collection class. For example, code for sorting often ends up in a collection called "SortedCollection," and code for applying a function to every element in a collection often ends up in an abstract base class called "Collection." This approach makes it hard to add new algorithms without editing and recompiling the vendor's source code, which is best to avoid for maintenance reasons.
Not type-safe-Several commercial collection classes are not type-safe. Use of these collections require heavy use of casting, which goes against one of the main spirits of C++ development (strict type checking).
Use of heap memory-All of the commercially available collection classes have their memory allocation policies woven deeply into the code of the containers. This means you cannot allocate space for a collection from shared memory instead of from the heap.

In response to these problems, the American National Standards Institute (ANSI) committee in conjunction with the International Standards Organization (ISO) decided to search for a standard set of collection classes that would overcome these difficulties. Alex Stepanov and Meng Lee proposed a template container and algorithms library based on their work in the area of generic programming. In July of 1994, their work was selected as the standard, and the Standard Template Library (STL) was born.

The Standard Template Library (STL) is comprised of the following components.

Containers- Generalized classes used to hold a collection of typed data
Iterators-Generalized pointers used to traverse the elements of a container
Algorithms-Procedures that can be applied on all or part of a container
Function Objects-Behaviors used as a parameter by a container or algorithm
Allocators-Objects responsible for allocating storage

Standards<ToolKit> includes an optimized implementation of the Standard Template Library, in addition to other components in the Standard C++ Library. A templatized string class supporting both ASCII and wide-character sets is included, as well as the Standard Exception Hierarchy and utility classes. Recursion Software firmly believes in standards conformance, and consequently all of our libraries use the Standard C++ Library both internally and in our class interfaces.