History
Origins (2006–2012)
Rust grew out of a personal project begun in 2006 byEvolution (2012–2019)
Rust'sMozilla layoffs and Rust Foundation (2020–present)
In August 2020, Mozilla laid off 250 of its 1,000 employees worldwide as part of a corporate restructuring caused by theSyntax and semantics
Hello World program
Below is a "Hello, World!" program in Rust. The keyword is used to denote a function, and theprintln!
macro prints the message to standard output. Statements in Rust are separated by semicolons.
Keywords and control flow
In Rust, blocks of code are delimited by curly brackets, and if
, else
, while
, and for
. Pattern matching is provided using the keyword. In the examples below, explanations are given in Expression blocks
Despite its syntactic resemblance to C and C++, Rust is more significantly influenced byif
expression also takes the place of C's ternary conditional. A function does not need to end with a return
expression: if the semicolon is omitted, the value of the last expression in the function will be used as the ..=
operator to create an inclusive range:
Types
Rust isunsafe
block. Rust instead uses an Option
type, which has two variants, Some(T)
(which indicates that a value is present) and None
(analogous to the null pointer). Option
implements a "null pointer optimization" avoiding any overhead for types which cannot have a null value (references or the NonZero
types, for example). Option
values must be handled using syntactic sugar, such as the if let
construction, in order to access the inner value (in this case, a string):
Generics
More advanced features in Rust include the use ofsum
are instantiated with the specific types that are needed by the code (in this case, sum of integers and sum of floats).
Generics can be used in functions to allow implementing a behavior for different types without repeating the same code. Generic functions can be written in relation to other generics, without knowing the actual type.
Ownership and lifetimes
Rust's ownership system consists of rules that ensure memory safety without using a garbage collector. In the system, each value in Rust must be attached to a variable called the owner of that value, and every value must have exactly one owner. Values are moved between different owners through assignment or passing a value as a function parameter. Values can also be ''borrowed,'' meaning that they are temporarily passed to a different function before being returned to the owner. With these rules, Rust can prevent the creation and use of dangling pointers:drop
function. This structure enforces the so-called resource acquisition is initialization (RAII) design pattern, in which resources, like file descriptors or network sockets, are tied to the lifetime of an object: when the object is dropped, the resource is closed.
The example below parses some configuration options from a string and creates a struct containing the options. The struct only contains references to the data, so for the struct to remain valid, the data referred to by the struct needs to be valid as well. The function signature for parse_config
specifies this relationship explicitly. In this example, the explicit lifetimes are unnecessary in newer Rust versions due to lifetime elision, which is an algorithm that automatically assigns lifetimes to functions if they are trivial.
Features
Rust aims to support concurrent systems programming, which has inspired a feature set with an emphasis on safety, control of memory layout, and concurrency.Memory safety
Rust is designed to be memory safe. It does not permit null pointers, dangling pointers, or data races. Data values can be initialized only through a fixed set of forms, all of which require their inputs to be already initialized. To replicate pointers being either valid orNULL
, such as in linked list or binary tree Some
value or None
. Rust has added syntax to manage lifetimes, which are checked at compile time by the ''borrow checker''. Unsafe code can subvert some of these restrictions using the unsafe
keyword. Unsafe code may also be used for low-level functionality like volatile memory access, architecture-specific intrinsics, type punning, and inline assembly.
Memory management
Rust does not use automated&
symbol do not involve run-time reference counting. The safety and validity of the underlying pointers is verified at compile time, preventing dangling pointers and other forms of undefined behavior. Rust's type system separates shared, immutable references of the form &T
from unique, mutable references of the form &mut T
. A mutable reference can be coerced to an immutable reference, but not vice versa.
Types and polymorphism
Rust's type system supports a mechanism called traits, inspired by type classes in the Haskell language, to define shared behavior between different types. For example, floats and integers both implement theAdd
trait because they can both be added; and any type that can be converted to a string implements the Display
or Debug
traits. This facility is known as ad hoc polymorphism.
Rust uses type inference for variables declared with the keyword let
. Such variables do not require a value to be initially assigned to determine their type. A compile time error results if any branch of code leaves the variable without an assignment. Variables assigned multiple times must be marked with the keyword mut
(short for mutable).
A function can be given add_one
function might require the type to implement Add
. This means that a generic function can be type-checked as soon as it is defined. The implementation of Rust generics is similar to the typical implementation of C++ templates: a separate copy of the code is generated for each instantiation. This is called monomorphization and contrasts with the type erasure scheme typically used in Java and Haskell. Type erasure is also available in Rust via the keyword dyn
(short for dynamic). Because monomorphization duplicates the code for each type used, it can result in more optimized code for specific use cases, but compile time and size of the output binary are also increased.
In Rust, user-defined types are created with the struct
or enum
keywords. The struct
keyword is used to denote a enum
s can take on different variants in runtime, with its capabilities similiar to algebraic data types found in functional programming languages. Both structs and enums can contain fields with different types. The impl
keyword can define methods for the types (data and functions are defined separately) or implement a trait for the types. Traits are used to restrict generic parameters and because traits can provide a type with more methods than the user defined. For example, the trait Iterator
requires that the next
method be defined for the type. Once the next
method is defined the trait provides common functional helper methods over the iterator like map
or filter
.
Type aliases, including generic arguments, can also be defined with the type
keyword.
The type system within Rust is based around implementations, traits and structured types. Implementations fulfill a role similar to that of classes within other languages and are defined with the keyword impl
. Traits provide inheritance and polymorphism; they allow Trait objects
Rust traits are implemented usingBox
where Tr
is a trait. For example, it is possible to create a list of objects which each can be printed out as follows: let v: Vec> = vec! ox::new(3), Box::new(5.0), Box::new("hi")/code>. Trait objects are dynamically sized; however, prior to the 2018 edition, the dyn
keyword was optional. A trait object is essentially a fat pointer that include a pointer as well as additional information about what type the pointer is.
Macros
It is possible to extend the Rust language using macros.
Declarative macros
A declarative macro (also called a "macro by example") is a macro that uses pattern matching to determine its expansion.
Procedural macros
Procedural macros use Rust functions that are compiled before other components to run and modify the compiler's input token
Token may refer to:
Arts, entertainment, and media
* Token, a game piece or counter, used in some games
* The Tokens, a vocal music group
* Tolkien Black, a recurring character on the animated television series ''South Park,'' formerly known a ...
stream. They are generally more flexible than declarative macros, but are more difficult to maintain due to their complexity.
Procedural macros come in three flavors:
* Function-like macros custom!(...)
* Derive macros # erive(CustomDerive)/code>
* Attribute macros # ustom_attribute/code>
The println!
macro is an example of a function-like macro and serde_derive
is a commonly used library for generating code
for reading and writing data in many formats such as JSON. Attribute macros are commonly used for language bindings such as the extendr
library for Rust bindings to R.
The following code shows the use of the Serialize
, Deserialize
and Debug
derive procedural macros
to implement JSON reading and writing as well as the ability to format a structure for debugging.
use serde_json::;
# erive(Serialize, Deserialize, Debug)struct Point
fn main()
Interface with C and C++
Rust has a foreign function interface (FFI) that can be used both to call code written in languages such as C from Rust and to call Rust code from those languages. Rust also has a library, CXX, for calling to or from C++. Rust and C differ in how they lay out structs in memory, so Rust structs may be given a # epr(C)/code> attribute, forcing the same layout as the equivalent C struct.
Components
Besides the compiler and standard library
In computer programming, a standard library is the library made available across implementations of a programming language. These libraries are conventionally described in programming language specifications; however, contents of a language's a ...
, the Rust ecosystem includes additional components for software development. Component installation is typically managed by , a Rust toolchain installer developed by the Rust project.
Standard library
The Rust standard library is split into three crates: , , and . When a project is annotated with the crate-level attribute , the crate is excluded.
Cargo
Cargo is Rust's build system and package manager. Cargo downloads, compiles, distributes, and uploads packages, called ''crates'', maintained in the official registry. Cargo also acts as a front-end for Clippy and other Rust components.
By default, Cargo sources its dependencies from the user-contributed registry ''crates.io'', but Git repositories and crates in the local filesystem and other external sources can be specified as dependencies, too.
Rustfmt
Rustfmt is a code formatter for Rust. It takes Rust source code as input and changes the whitespace and indentation to produce code formatted in accordance to a common style unless specified otherwise. Rustfmt can be invoked as a standalone program or on a Rust project through Cargo.
Clippy
Clippy is Rust's built-in linting
Lint, or a linter, is a static code analysis tool used to flag programming errors, bugs, stylistic errors and suspicious constructs. The term originates from a Unix utility that examined C language source code.
History
Stephen C. Johnson, a c ...
tool to improve the correctness, performance, and readability of Rust code. It was created in 2014 and named after the eponymous Microsoft Office feature. As of 2021, Clippy has more than 450 rules, which can be browsed online and filtered by category.
Versioning system
Following Rust 1.0, new features are developed in ''nightly'' versions which release on a daily basis. During each release cycle of six weeks, changes on nightly versions are released to beta, while changes from the previous beta version are released to a new stable version.
Every three years, a new "edition" is produced. Editions are released to provide an easy reference point for changes due to the frequent nature of Rust's ''train release schedule,'' and to provide a window to make limited breaking changes. Editions are largely compatible and migration to a new edition is assisted with automated tooling.
IDE support
The most popular language server for Rust is ''rust-analyzer''. The original language server, ''RLS'' was officially deprecated in favor of ''rust-analyzer'' in July 2022. These projects provide IDEs and text editors with more information about a Rust project, with basic features including autocompletion
Autocomplete, or word completion, is a feature in which an application predicts the rest of a word a user is typing. In Android and iOS smartphones, this is called predictive text. In graphical user interfaces, users can typically press the t ...
, and display of compilation errors while editing.
Performance
Rust aims "to be as efficient and portable as idiomatic C++, without sacrificing safety". Rust does not perform garbage collection, which allows it to be more efficient and performant than other memory-safe languages.
Rust provides two "modes": safe and unsafe. The safe mode is the "normal" one, in which most Rust is written. In unsafe mode, the developer is responsible for the correctness of the code, making it possible to create applications which require low-level features. It has been demonstrated empirically that unsafe Rust is not always more performant than safe Rust, and can even be slower in some cases.
Many of Rust's features are so-called ''zero-cost abstractions'', meaning they are optimized away at compile time and incur no runtime penalty. The ownership and borrowing system permits zero-copy
"Zero-copy" describes computer operations in which the CPU does not perform the task of copying data from one memory area to another or in which unnecessary data copies are avoided. This is frequently used to save CPU cycles and memory bandwi ...
implementations for some performance-sensitive tasks, such as parsing
Parsing, syntax analysis, or syntactic analysis is the process of analyzing a string of symbols, either in natural language, computer languages or data structures, conforming to the rules of a formal grammar. The term ''parsing'' comes from ...
. Static dispatch is used by default to eliminate method calls, with the exception of methods called on dynamic trait objects. The compiler also uses inline expansion to eliminate function calls and statically dispatched method invocations entirely.
Since Rust utilizes LLVM, any performance improvements in LLVM also carry over to Rust. Unlike C and C++, Rust allows re-organizing struct and enum element ordering. This can be done to reduce the size of structures in memory, for better memory alignment, and to improve cache access efficiency.
Adoption
According to the Stack Overflow Developer Survey in 2022, 9% of respondents have recently done extensive development in Rust. The survey has additionally named Rust the "most loved programming language" every year from 2016 to 2022 (inclusive), a ranking based on the number of current developers who express an interest in continuing to work in the same language. In 2022, Rust tied with Python for "most wanted technology" with 18% of developers not currently working in Rust expressing an interest in doing so.
Rust has been adopted for components at a number of major software companies, including Amazon
Amazon most often refers to:
* Amazons, a tribe of female warriors in Greek mythology
* Amazon rainforest, a rainforest covering most of the Amazon basin
* Amazon River, in South America
* Amazon (company), an American multinational technolog ...
, Discord, Dropbox, Facebook
Facebook is an online social media and social networking service owned by American company Meta Platforms. Founded in 2004 by Mark Zuckerberg with fellow Harvard College students and roommates Eduardo Saverin, Andrew McCollum, Dust ...
( Meta), Google (Alphabet
An alphabet is a standardized set of basic written graphemes (called letters) that represent the phonemes of certain spoken languages. Not all writing systems represent language in this way; in a syllabary, each character represents a syllab ...
), and Microsoft.
Web browsers and services
* Firefox has two projects written in Rust: the Servo parallel
Parallel is a geometric term of location which may refer to:
Computing
* Parallel algorithm
* Parallel computing
* Parallel metaheuristic
* Parallel (software), a UNIX utility for running programs in parallel
* Parallel Sysplex, a cluster o ...
browser engine developed by Mozilla in collaboration with Samsung
The Samsung Group (or simply Samsung) ( ko, 삼성 ) is a South Korean multinational manufacturing conglomerate headquartered in Samsung Town, Seoul, South Korea. It comprises numerous affiliated businesses, most of them united under the ...
; and Quantum
In physics, a quantum (plural quanta) is the minimum amount of any physical entity ( physical property) involved in an interaction. The fundamental notion that a physical property can be "quantized" is referred to as "the hypothesis of quantizat ...
, which is composed of several sub-projects for improving Mozilla's Gecko browser engine.
* OpenDNS uses Rust in some of its internal projects.
* Deno, a secure runtime for JavaScript
JavaScript (), often abbreviated as JS, is a programming language that is one of the core technologies of the World Wide Web, alongside HTML and CSS. As of 2022, 98% of websites use JavaScript on the client side for webpage behavior, of ...
and TypeScript, is built with V8, Rust, and Tokio
Tokio may refer to:
* , the capital of Japan, used primarily in non-English-speaking countries
may also refer to:
Music
* Tokio (band), a Japanese pop/rock band
** ''Tokio'' (album), their debut album
* Tokio Hotel, a German rock band
* Toki ...
.
* Amazon Web Services has multiple projects written in Rust, including Firecracker, a virtualization solution, and Bottlerocket, a Linux distribution and containerization solution.
* Cloudflare's implementations of the QUIC protocol and firewall
Firewall may refer to:
* Firewall (computing), a technological barrier designed to prevent unauthorized or unwanted communications between computer networks or hosts
* Firewall (construction), a barrier inside a building, designed to limit the spre ...
rules are written in Rust.
* Arti is a Rust implementation of Tor server by The Tor Project
The Tor Project, Inc. is a Seattle-based 501(c)(3) research-education nonprofit organization founded by computer scientists Roger Dingledine, Nick Mathewson and five others. The Tor Project is primarily responsible for maintaining software f ...
.
Operating systems
* Redox
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or ...
is a "full-blown Unix-like operating system" including a microkernel written in Rust.
* Theseus, an experimental operating system described as having "intralingual design": leveraging Rust's programming language mechanisms for implementing the OS.
* The Google Fuchsia
''Fuchsia'' () is a genus of flowering plants that consists mostly of shrubs or small trees. The first to be scientifically described, '' Fuchsia triphylla'', was discovered on the Caribbean island of Hispaniola (Haiti and the Dominican Republic ...
capability-based security operating system has components written in Rust, including a TCP/IP
The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the set of communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the su ...
library.
* Stratis is a file system manager written in Rust for Fedora
A fedora () is a hat with a soft brim and indented crown.Kilgour, Ruth Edwards (1958). ''A Pageant of Hats Ancient and Modern''. R. M. McBride Company. It is typically creased lengthwise down the crown and "pinched" near the front on both side ...
and RHEL.
* is a Unix/Linux command line alternative to written in Rust.
* Rust for Linux is a patch series begun in 2021 to add Rust support to the Linux kernel.
* LynxOS
The LynxOS RTOS is a Unix-like real-time operating system from Lynx Software Technologies (formerly "LynuxWorks"). Sometimes known as the Lynx Operating System, LynxOS features full POSIX conformance and, more recently, Linux compatibility. L ...
-178 and LynxElement unikernel support Rust in their certified toolchain, as of late 2022.
Other notable projects and platforms
* Discord uses Rust for portions of its backend, as well as client-side video encoding, to augment the core infrastructure written in Elixir.
* Microsoft Azure IoT Edge, a platform used to run Azure services and artificial intelligence on IoT devices, has components implemented in Rust.
* Polkadot is an open source blockchain
A blockchain is a type of distributed ledger technology (DLT) that consists of growing lists of records, called ''blocks'', that are securely linked together using cryptography. Each block contains a cryptographic hash of the previous block, ...
platform and cryptocurrency
A cryptocurrency, crypto-currency, or crypto is a digital currency designed to work as a medium of exchange through a computer network that is not reliant on any central authority, such as a government or bank, to uphold or maintain it. It i ...
written in Rust.
* Ruffle is an open-source SWF
SWF ( ) is an Adobe Flash file format used for multimedia, vector graphics and ActionScript.Open Screen Pr ...
emulator written in Rust.
* TerminusDB, an open source graph database designed for collaboratively building and curating knowledge graphs, is written in Prolog and Rust.
Community
Conferences
Rust's official website lists online forums, messaging platforms, and in-person meetups for the Rust community. Conferences dedicated to Rust development include:
* RustConf: an annual conference in Portland, Oregon
Portland (, ) is a port city in the Pacific Northwest and the largest city in the U.S. state of Oregon. Situated at the confluence of the Willamette and Columbia rivers, Portland is the county seat of Multnomah County, the most populous ...
. Held annually since 2016 (except in 2020 and 2021 because of the COVID-19 pandemic
The COVID-19 pandemic, also known as the coronavirus pandemic, is an ongoing global pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The novel virus was first identi ...
).
* Rust Belt Rust: a #rustlang conference in the Rust Belt
The Rust Belt is a region of the United States that experienced industrial decline starting in the 1950s. The U.S. manufacturing sector as a percentage of the U.S. GDP peaked in 1953 and has been in decline since, impacting certain regions an ...
* RustFest: Europe's @rustlang conference
* RustCon Asia
* Rust LATAM
* Oxidize Global
Rust Foundation
The Rust Foundation is a non-profit
A nonprofit organization (NPO) or non-profit organisation, also known as a non-business entity, not-for-profit organization, or nonprofit institution, is a legal entity organized and operated for a collective, public or social benefit, in co ...
membership organization
A membership organization is any organization that allows people or entities to subscribe, and often requires them to pay a membership fee or "subscription". Membership organizations typically have a particular purpose, which involves connecting pe ...
incorporated in United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...
, with the primary purposes of backing the technical project as a legal entity and helping to manage the trademark and infrastructure assets.
It was established on February 8, 2021, with five founding corporate members (Amazon Web Services, Huawei, Google, Microsoft, and Mozilla). The foundation's board is chaired by Shane Miller. Starting in late 2021, its Executive Director and CEO is Rebecca Rumbul. Prior to this, Ashley Williams was interim executive director.
Governance teams
The Rust project is composed of ''teams'' that are responsible for different subareas of the development. For example, the Core team is responsible for "managing the overall direction of Rust, subteam leadership, and any cross-cutting issues," the Compiler team is responsible for "developing and managing compiler internals and optimizations," and the Language team is responsible for "designing and helping to implement new language features," according to the official website.
See also
* Comparison of programming languages
* History of programming languages
* List of programming languages
* List of programming languages by type
Notes
References
Book sources
*
Others
Further reading
*
External links
*
{{Authority control
2010 software
Articles with example code
Concurrent programming languages
Free compilers and interpreters
Free software projects
Functional languages
High-level programming languages
Mozilla
Multi-paradigm programming languages
Pattern matching programming languages
Procedural programming languages
Programming languages created in 2010
Software using the Apache license
Software using the MIT license
Statically typed programming languages
Systems programming languages