Utility library

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Diagnostics library

Memory management library

Metaprogramming library (C++11)

General utilities library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library (C++17)

Concurrency support library (C++11)

Execution support library (C++26)

Technical specifications

Symbols index

External libraries

 

Utilities library

Language support Type support (basic types, RTTI) Library feature-test macros (C++20) Program utilities Coroutine support (C++20) Variadic functions is_constant_evaluated (C++20) is_within_lifetime (C++26) initializer_list (C++11) source_location (C++20) Three-way comparison three_way_comparablethree_way_comparable_with (C++20)(C++20) strong_ordering (C++20) weak_ordering (C++20) partial_ordering (C++20) common_comparison_category (C++20) compare_three_way_result (C++20) compare_three_way (C++20) strong_order (C++20) weak_order (C++20) partial_order (C++20) compare_strong_order_fallback (C++20) compare_weak_order_fallback (C++20) compare_partial_order_fallback (C++20)   is_eqis_ltis_lteq (C++20)(C++20)(C++20)   is_neqis_gtis_gteq (C++20)(C++20)(C++20)

General utilities Function objects Bit manipulation (C++20) bitset hash (C++11) Relational operators (deprecated in C++20) rel_ops::operator!=rel_ops::operator>    rel_ops::operator<=rel_ops::operator>= Integer comparison functions cmp_equalcmp_lesscmp_less_than (C++20)(C++20)(C++20)   cmp_not_equalcmp_greatercmp_greater_than (C++20)(C++20)(C++20) in_range (C++20) Swap and type operations swap ranges::swap (C++20) exchange (C++14) declval (C++11) to_underlying (C++23) forward (C++11) forward_like (C++23) move (C++11) move_if_noexcept (C++11) as_const (C++17) Common vocabulary types pair tuple (C++11) optional (C++17) any (C++17) variant (C++17) tuple_size (C++11) tuple_element (C++11) apply (C++17) make_from_tuple (C++17) expected (C++23)

 

C++ includes a variety of utility libraries that provide functionality ranging from bit-counting to partial function application. These libraries can be broadly divided into two groups:

• language support libraries, and
• general-purpose libraries.

Language support

Language support libraries provide classes and functions that interact closely with language features and support common language idioms.

Type support

Basic types (e.g. std::size_t, std::nullptr_t), RTTI (e.g. std::type_info)

Metaprogramming (since C++11)

Type traits (e.g. std::is_integral, std::rank), compile-time constants (e.g. std::integer_sequence, std::ratio)

Constant evaluation context (since C++20)

Defined in header <type_traits>
is_constant_evaluated (C++20)	detects whether the call occurs within a constant-evaluated context (function)
is_within_lifetime (C++26)	checks whether a pointer is within the object's lifetime at compile time (function)

Implementation properties (since C++20)

The header <version> supplies implementation-dependent information about the C++ standard library (such as the version number and release date). It also defines the library feature-test macros.

Program utilities

Termination (e.g. std::abort, std::atexit), environment (e.g. std::system), signals (e.g. std::raise)

Dynamic memory management

Smart pointers (e.g. std::shared_ptr), allocators (e.g. std::allocator or std::pmr::memory_resource), C-style memory management (e.g. std::malloc)

Error handling

Exceptions (e.g. std::exception, std::terminate), assertions (e.g. assert)

Source code information capture (since C++20)

Defined in header <source_location>
source_location (C++20)	a class representing information about the source code, such as file names, line numbers, and function names (class)

Initializer lists (since C++11)

Defined in header <initializer_list>
initializer_list (C++11)	references a temporary array created in list-initialization (class template)

Three-way comparison (since C++20)

Defined in header <compare>
three_way_comparablethree_way_comparable_with (C++20)	specifies that operator <=> produces consistent result on given types (concept)
partial_ordering (C++20)	the result type of 3-way comparison that supports all 6 operators, is not substitutable, and allows incomparable values (class)
weak_ordering (C++20)	the result type of 3-way comparison that supports all 6 operators and is not substitutable (class)
strong_ordering (C++20)	the result type of 3-way comparison that supports all 6 operators and is substitutable (class)
is_eqis_neqis_ltis_lteqis_gtis_gteq (C++20)	named comparison functions (function)
compare_three_way (C++20)	constrained function object implementing x <=> y (class)
compare_three_way_result (C++20)	obtains the result type of the three-way comparison operator <=> on given types (class template)
common_comparison_category (C++20)	the strongest comparison category to which all of the given types can be converted (class template)
strong_order (C++20)	performs 3-way comparison and produces a result of type std::strong_ordering (customization point object)
weak_order (C++20)	performs 3-way comparison and produces a result of type std::weak_ordering (customization point object)
partial_order (C++20)	performs 3-way comparison and produces a result of type std::partial_ordering (customization point object)
compare_strong_order_fallback (C++20)	performs 3-way comparison and produces a result of type std::strong_ordering, even if operator<=> is unavailable (customization point object)
compare_weak_order_fallback (C++20)	performs 3-way comparison and produces a result of type std::weak_ordering, even if operator<=> is unavailable (customization point object)
compare_partial_order_fallback (C++20)	performs 3-way comparison and produces a result of type std::partial_ordering, even if operator<=> is unavailable (customization point object)

Coroutine support (since C++20)

Types for coroutine support, e.g. std::coroutine_traits, std::coroutine_handle.

Variadic functions

Support for functions that take an arbitrary number of parameters (via e.g. va_start, va_arg, va_end).

General-purpose utilities

Swap

Defined in header <utility>
swap	swaps the values of two objects (function template)
exchange (C++14)	replaces the argument with a new value and returns its previous value (function template)
Defined in header <concepts>
ranges::swap (C++20)	swaps the values of two objects (customization point object)

Type operations (since C++11)

Defined in header <utility>
forward (C++11)	forwards a function argument and use the type template argument to preserve its value category (function template)
forward_like (C++23)	forwards a function argument as if casting it to the value category and constness of the expression of specified type template argument (function template)
move (C++11)	converts the argument to an xvalue (function template)
move_if_noexcept (C++11)	converts the argument to an xvalue if the move constructor does not throw (function template)
as_const (C++17)	obtains a reference to const to its argument (function template)
declval (C++11)	obtains a reference to an object of the template type argument for use in an unevaluated context (function template)
to_underlying (C++23)	converts an enumeration to its underlying type (function template)

Integer comparison functions (since C++20)

Defined in header <utility>
cmp_equalcmp_not_equalcmp_lesscmp_greatercmp_less_equalcmp_greater_equal (C++20)	compares two integer values, ensuring that signed negative numbers are less than unsigned numbers (function template)
in_range (C++20)	checks if an integer value is in the range of a given integer type (function template)

Relational operators (until C++20)

Defined in header <utility>
Defined in namespace std::rel_ops
operator!=operator>operator<=operator>= (deprecated in C++20)	automatically generates comparison operators based on user-defined operator== and operator< (function template)

Construction tags (since C++11)

Defined in header <utility>
piecewise_constructpiecewise_construct_t (C++11)	piecewise construction tag (tag)
in_placein_place_typein_place_indexin_place_tin_place_type_tin_place_index_t (C++17)	in-place construction tag (tag)
nontype nontype_t (C++26)	value construction tag (tag)

Pairs and tuples

Defined in header <utility>
pair	implements binary tuple, i.e. a pair of values (class template)
Defined in header <tuple>
tuple (C++11)	implements fixed size container, which holds elements of possibly different types (class template)
apply (C++17)	calls a function with a tuple of arguments (function template)
make_from_tuple (C++17)	construct an object with a tuple of arguments (function template)
Tuple protocol (since C++11)
Defined in header <tuple>
Defined in header <utility>
Defined in header <array>
Defined in header <ranges>
Defined in header <complex>
tuple_size (C++11)	obtains the number of elements of a tuple-like type (class template)
tuple_element (C++11)	obtains the element types of a tuple-like type (class template)

Sum types and type erased wrappers (since C++17)

Defined in header <optional>
optional (C++17)	a wrapper that may or may not hold an object (class template)
Defined in header <expected>
expected (C++23)	a wrapper that contains either an expected or error value (class template)
Defined in header <variant>
variant (C++17)	a type-safe discriminated union (class template)
Defined in header <any>
any (C++17)	objects that hold instances of any CopyConstructible type (class)

Bitset

Defined in header <bitset>
bitset	implements constant length bit array (class template)

Bit manipulation (since C++20)

The header <bit> provides several function templates to access, manipulate, and process individual bits and bit sequences. The byte ordering (endianness) of scalar types can be inspected via std::endian facility.

Function objects (since C++11)

Partial function application (e.g. std::bind) and related utilities: utilities for binding such as std::ref and std::placeholders, polymorphic function wrappers: std::function, predefined functors (e.g. std::plus, std::equal_to), pointer-to-member to function converters std::mem_fn.

Hash support (since C++11)

Defined in header <functional>
hash (C++11)	hash function object (class template)

See also

C documentation for Utility library