C++ Standard Library

In the C++ programming language, the C++ Standard Library is a collection of classes and functions, which are written in the core language and part of the C++ ISO Standard itself.[1]

OverviewEdit

The C++ Standard Library provides several generic containers, functions to use and manipulate these containers, function objects, generic strings and streams (including interactive and file I/O), support for some language features, and functions for everyday tasks such as finding the square root of a number. The C++ Standard Library also incorporates most headers of the ISO C standard library ending with ".h", but their use is deprecated.[2] No other headers in the C++ Standard Library end in ".h". Features of the C++ Standard Library are declared within the std namespace.

The C++ Standard Library is based upon conventions introduced by the Standard Template Library (STL), and has been influenced by research in generic programming and developers of the STL such as Alexander Stepanov and Meng Lee.[3][4] Although the C++ Standard Library and the STL share many features, neither is a strict superset of the other.[citation needed]

A noteworthy feature of the C++ Standard Library is that it not only specifies the syntax and semantics of generic algorithms, but also places requirements on their performance.[5] These performance requirements often correspond to a well-known algorithm, which is expected but not required to be used. In most cases this requires linear time O(n) or linearithmic time O(n log n), but in some cases higher bounds are allowed, such as quasilinear time O(n log2 n) for stable sort (to allow in-place merge sort). Previously, sorting was only required to take O(n log n) on average, allowing the use of quicksort, which is fast in practice but has poor worst-case performance, but introsort was introduced to allow both fast average performance and optimal worst-case complexity, and as of C++11, sorting is guaranteed to be at worst linearithmic. In other cases requirements remain laxer, such as selection, which is only required to be linear on average (as in quickselect),[6] not requiring worst-case linear as in introselect.

The C++ Standard Library underwent ISO standardization as part of the C++ ISO Standardization effort, and is undergoing further work[7] regarding standardization of expanded functionality.

ImplementationsEdit

Name Homepage Acronym Licence Latest release
GNU C++ Standard Library [1] libstdc++ GPLv3 11/15/2021
LLVM C++ Standard Library [2] libc++ Apache License v2.0 with LLVM Exceptions 9/30/2021
NVIDIA C++ Standard Library [3] libcu++ Apache License v2.0 with LLVM Exceptions 8/9/2021
Microsoft C++ Standard Library [4] MSVC STL Apache License v2.0 with LLVM Exceptions 12/16/2021
HPX C++ Standard Library for Parallelism and Concurrency [5] HPX Boost Software License 1.0 8/12/2021
Electronic Arts Standard Template Library [6] EASTL BSD 3-Clause License 10/20/2021
Dinkum C++ Library [7] Unknown Commercial Unknown
Cray C++ Standard Library [8] Unknown Commercial Unknown

DiscontinuedEdit

Apache C++ Standard LibraryEdit

The Apache C++ Standard Library is another open source implementation. It was originally developed commercially by Rogue Wave Software and later donated to the Apache Software Foundation.[8] However, after more than five years without a release, the board of the Apache Software Foundation decided to end this project and move it to Apache Attic.[9]

See alsoEdit

The following libraries implement much of the C++ Standard Library:

Name Homepage Description
Abseil [9] An open source collection of libraries used internally by Google
Folly [10] A variety of C++ 14 libraries that are used extensively by Facebook
Bareflank Support Library [11] An C++ library where everything can be executed at compile time

Standard headersEdit

The following files contain the declarations of the C++ Standard Library.

GeneralEdit

<any>
New in C++17. Provides a type-erased class std::any.
<atomic>
New in C++11. Provides class template std::atomic, its several template specializations, and more atomic operations.
<chrono>
Provides time elements, such as std::chrono::duration, std::chrono::time_point, and clocks. Since C++20, new additions were added: calendars, time zones, more clocks, and string chrono formatting.
<concepts>
New in C++20. Provides fundamental library concepts.
<expected>
New in C++23. Provides class template std::expected, a result type.
<functional>
Provides several function objects, designed for use with the standard algorithms.
<memory>
Provides facilities for memory management in C++, including the class template std::unique_ptr.
<memory_resource>
New in C++17. Provides facilities for creating polymorphic memory allocators whose behaviors can change at runtime.[10]
<scoped_allocator>
New in C++11. Provides std::scoped_allocator_adaptor.
<stdexcept>
Contains standard exception classes such as std::logic_error and std::runtime_error, both derived from std::exception.
<system_error>
New in C++11. Defines std::error_code
<optional>
New in C++17. Provides class template std::optional, an optional type.
<stacktrace>
New in C++23. Provides stack trace operations.
<tuple>
New in C++11 and TR1. Provides a class template std::tuple, a tuple.
<type_traits>
New in C++11. Provides metaprogramming facilities working with types.
<utility>
Provides various utilities: class template std::pair (two-member tuples), compile-time integer sequences, helpers in constructing vocabulary types, functions such as std::move and std::forward, and many more. The namespace std::rel_ops for automatically generating comparison operators is deprecated in C++20 in favor of new defaulted comparison operators.
<variant>
New in C++17. Provides a class template std::variant, a tagged union type.

Language supportEdit

<compare>
New in C++20. Provides three-way comparison operator support.
<coroutine>
New in C++20. Provides coroutine support.
<exception>
Provides several types and functions related to exception handling, including std::exception, the base class of all exceptions thrown by the Standard Library.
<initializer_list>
New in C++11. Provides initializer list support.
<limits>
Provides the class template std::numeric_limits, used for describing properties of fundamental numeric types.
<new>
Provides operators new and delete and other functions and types composing the fundamentals of C++ memory management.
<source_location>
New in C++20. Provides capturing source location information as alternative to predefined macros such as __LINE__.
<typeinfo>
Provides facilities for working with C++ run-time type information.
<version>
New in C++20. Provides information about the implementation of the C++ standard library.[11]

ContainersEdit

<array>
New in C++11 and TR1. Provides the container class template std::array, a container for a fixed sized array.
<bitset>
Provides the specialized container class std::bitset, a bit array.
<deque>
Provides the container class template std::deque, a double-ended queue.
<forward_list>
New in C++11 and TR1. Provides the container class template std::forward_list, a singly linked list.
<list>
Provides the container class template std::list, a doubly linked list.
<map>
Provides the container class templates std::map and std::multimap, sorted associative array and multimap.
<queue>
Provides the container adapter class std::queue, a single-ended queue, and std::priority_queue, a priority queue.
<set>
Provides the container class templates std::set and std::multiset, sorted associative containers or sets.
<span>
New in C++20. Provides the container adapter class template std::span, a mutable non-owning view that refers to any contiguous range.
<stack>
Provides the container adapter class std::stack, a stack.
<unordered_map>
New in C++11 and TR1. Provides the container class template std::unordered_map and std::unordered_multimap, hash tables.
<unordered_set>
New in C++11 and TR1. Provides the container class template std::unordered_set and std::unordered_multiset.
<vector>
Provides the container class template std::vector, a dynamic array.

Iterators and RangesEdit

<algorithm>
Provides definitions of many container algorithms.
<execution>
New in C++17. Provides execution policies for parallelized algorithms.
<iterator>
Provides classes and templates for working with iterators.
<ranges>
New in C++20. Provides ranges facilities and lazy evaluated adaptors.

LocalizationEdit

<locale>
Defines classes and declares functions that encapsulate and manipulate the information peculiar to a locale.
<codecvt>
Provides code conversion facets for various character encodings. This header is deprecated since C++17.

StringsEdit

<charconv>
New in C++17. Provides a locale-independent, non-allocating, and non-throwing string conversion utilities from/to integers and floating points.
<format>
New in C++20. Provides a modern way of formatting strings including std::format.
<string>
Provides the C++ standard string classes and templates.
<string_view>
New in C++17. Provides class template std::basic_string_view, an immutable non-owning view to any string.
<regex>
New in C++11. Provides utilities for pattern matching strings using regular expressions.

Streams, Files, and Input/OutputEdit

<filesystem>
New in C++17. Provides facilities for file system operations and their components.
<fstream>
Provides facilities for file-based input and output. See fstream.
<iomanip>
Provides facilities to manipulate output formatting, such as the base used when formatting integers and the precision of floating point values.
<ios>
Provides several types and functions basic to the operation of iostreams.
<iosfwd>
Provides forward declarations of several I/O-related class templates.
<iostream>
Provides C++ input and output fundamentals. See iostream.
<istream>
Provides std::istream and other supporting classes for input.
<ostream>
Provides std::ostream and other supporting classes for output.
<spanstream>
New in C++23. Provides std::spanstream and other fixed character buffer I/O streams.
<sstream>
Provides std::stringstream and other supporting classes for string manipulation.
<streambuf>
Provides reading and writing functionality to/from certain types of character sequences, such as external files or strings.
<syncstream>
New in C++20. Provides std::osyncstream and other supporting classes for synchronized output streams.

Thread support libraryEdit

<barrier>
New in C++20. Provides std::barrier, a reusable thread barrier.
<condition_variable>
New in C++11. In 32.6-1, condition variables provide synchronization primitives used to block a thread until notified by some other thread that some condition is met or until a system time is reached.
<future>
New in C++11. In 32.9.1-1, this section describes components that a C++ program can use to retrieve in one thread the result (value or exception) from a function that has run in the same thread or another thread.
<latch>
New in C++20. Provides std::latch, a single-use thread barrier.
<mutex>
New in C++11. In 32.5-1, this section provides mechanisms for mutual exclusion: mutexes, locks, and call once.
<shared_mutex>
New in C++14. Provides facitility for shared mutual exclusion.
<semaphore>
New in C++20. Provides semaphore that models non-negative resource count.
<stop_token>
New in C++20. In 32.3.1-1, this section describes components that can be used to asynchronously request that an operation stops execution in a timely manner, typically because the result is no longer required. Such a request is called a stop request.
<thread>
New in C++11. Provide class and namespace for working with threads.

Numerics libraryEdit

Components that C++ programs may use to perform seminumerical operations.

<bit>
New in C++20. Provides bit manipulation facility.
<complex>
Defines a class template std::complex, and numerous functions for representing and manipulating complex numbers.
<numbers>
New in C++20. Provides mathematical constants defined in namespace std::numbers.
<random>
New in C++11. Facility for generating (pseudo-)random numbers and distributions.
<ratio>
New in C++11. Provides compile-time rational arithmetic based on class templates.
<valarray>
Defines five class templates (std::valarray, std::slice_array, std::gslice_array, std::mask_array, and std::indirect_array), two classes (std::slice and std::gslice), and a series of related function templates for representing and manipulating arrays of values.
<numeric>
Generalized numeric operations.

C standard libraryEdit

Each header from the C Standard Library is included in the C++ Standard Library under a different name, generated by removing the .h, and adding a 'c' at the start; for example, 'time.h' becomes 'ctime'. The only difference between these headers and the traditional C Standard Library headers is that where possible the functions should be placed into the std:: namespace. In ISO C, functions in the standard library are allowed to be implemented by macros, which is not allowed by ISO C++.

See alsoEdit

NotesEdit

ReferencesEdit

  1. ^ ISO/IEC 14882:2003(E) Programming Languages – C++ §17-27
  2. ^ ISO/IEC 14882:2003(E) Programming Languages – C++ §D.5
  3. ^ Bjarne Stroustrup (1994). The Design and Evolution of C++ §8.5. Addison Wesley. ISBN 0-201-54330-3.
  4. ^ Alexander Stepanov, Meng Lee (1 August 1994). "The Standard Template Library". HP Labs. Retrieved 22 October 2017.
  5. ^ "Generic Algorithms", David Musser
  6. ^ "std::nth_element". cppreference.com. Retrieved 20 March 2018.
  7. ^ "JTC1/SC22/WG21 – The C++ Standards Committee". ISO/IEC. Retrieved 7 July 2009.
  8. ^ Apache C++ Standard Library
  9. ^ Brett Porter (18 July 2013). "Apache C++ Standard Library and the Attic". stdcxx-dev mailing list. Retrieved 27 February 2014.
  10. ^ Filipek, Bartlomiej. "Polymorphic Allocators, std::vector Growth and Hacking". Retrieved 30 April 2021.
  11. ^ "Working Draft, Standard for Programming Language C++" (PDF). open-std.org. ISO/IEC. 1 April 2020. p. 492. Archived (PDF) from the original on 27 April 2020. Retrieved 30 April 2021.

Further readingEdit

External linksEdit