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109-484: Go is a fast statically typed , compiled high-level general purpose programming language . It is known for its simplicity and efficiency. It was designed at Google in 2009 by Robert Griesemer , Rob Pike , and Ken Thompson . It is syntactically similar to C , but also has memory safety , garbage collection , structural typing , and CSP -style concurrency . It is often referred to as Golang because of its former domain name, golang.org , but its proper name

218-540: A map [ string ] interface {} (map of string to empty interface). This recursively describes data in the form of a dictionary with string keys and values of any type. Interface values are implemented using pointer to data and a second pointer to run-time type information. Like some other types implemented using pointers in Go, interface values are nil if uninitialized. Since version 1.18, Go supports generic code using parameterized types. Functions and types now have

327-475: A dependent type or an effect system , which enables even more program specifications to be verified by a type checker. Beyond simple value-type pairs, a virtual "region" of code is associated with an "effect" component describing what is being done with what , and enabling for example to "throw" an error report. Thus the symbolic system may be a type and effect system , which endows it with more safety checking than type checking alone. Whether automated by

436-412: A computer program 's execution, the values are placed into temporary storage, then execution jumps to the code of the invoked function. The invoked function's code accesses the values and makes use of them. If the instructions inside the function are written with the assumption of receiving an integer value, but the calling code passed a floating-point value , then the wrong result will be computed by

545-423: A runtime error . To prove the absence of these defects, other kinds of formal methods , collectively known as program analyses , are in common use. Alternatively, a sufficiently expressive type system, such as in dependently typed languages, can prevent these kinds of errors (for example, expressing the type of non-zero numbers ). In addition, software testing is an empirical method for finding errors that such

654-540: A static type system . It was designed to be compiled to provide low-level access to memory and language constructs that map efficiently to machine instructions , all with minimal runtime support . Despite its low-level capabilities, the language was designed to encourage cross-platform programming. A standards -compliant C program written with portability in mind can be compiled for a wide variety of computer platforms and operating systems with few changes to its source code. Since 2000, C has consistently ranked among

763-452: A certain platform or with a particular compiler, due, for example, to the use of non-standard libraries, such as GUI libraries, or to a reliance on compiler- or platform-specific attributes such as the exact size of data types and byte endianness . In cases where code must be compilable by either standard-conforming or K&R C-based compilers, the __STDC__ macro can be used to split the code into Standard and K&R sections to prevent

872-422: A computer program, and then checking that the parts have been connected in a consistent way. This checking can happen statically (at compile time ), dynamically (at run time ), or as a combination of both. Type systems have other purposes as well, such as expressing business rules, enabling certain compiler optimizations , allowing for multiple dispatch , and providing a form of documentation . An example of

981-400: A data type, termed typing , gives meaning to a sequence of bits such as a value in memory or some object such as a variable . The hardware of a general purpose computer is unable to discriminate between for example a memory address and an instruction code , or between a character , an integer , or a floating-point number , because it makes no intrinsic distinction between any of

1090-801: A dynamic check is needed to verify that the operation is safe. This requirement is one of the criticisms of downcasting. By definition, dynamic type checking may cause a program to fail at runtime. In some programming languages, it is possible to anticipate and recover from these failures. In others, type-checking errors are considered fatal. Programming languages that include dynamic type checking but not static type checking are often called "dynamically typed programming languages". Some languages allow both static and dynamic typing. For example, Java and some other ostensibly statically typed languages support downcasting types to their subtypes , querying an object to discover its dynamic type and other type operations that depend on runtime type information. Another example

1199-457: A function type; thus, func(string, int32) (int, error) is the type of functions that take a string and a 32-bit signed integer, and return a signed integer (of default width) and a value of the built-in interface type error . Any named type has a method set associated with it. The IP address example above can be extended with a method for checking whether its value is a known standard: Due to nominal typing, this method definition adds

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1308-475: A language can be statically typed without requiring type declarations (examples include Haskell , Scala , OCaml , F# , Swift , and to a lesser extent C# and C++ ), so explicit type declaration is not a necessary requirement for static typing in all languages. Dynamic typing allows constructs that some (simple) static type checking would reject as illegal. For example, eval functions, which execute arbitrary data as code, become possible. An eval function

1417-469: A limited form of structural typing in the otherwise nominal type system of Go. An object which is of an interface type is also of another type, much like C++ objects being simultaneously of a base and derived class. Go interfaces were designed after protocols from the Smalltalk programming language. Multiple sources use the term duck typing when describing Go interfaces. Although the term duck typing

1526-513: A line of code divides two integers, and is passed a string of letters instead of an integer. It is an unintended condition which might manifest in multiple stages of a program's development. Thus a facility for detection of the error is needed in the type system. In some languages, such as Haskell , for which type inference is automated, lint might be available to its compiler to aid in the detection of error. Type safety contributes to program correctness , but might only guarantee correctness at

1635-405: A method to ipv4addr , but not on uint32 . While methods have special definition and call syntax, there is no distinct method type. Go provides two features that replace class inheritance . The first is embedding , which can be viewed as an automated form of composition . The second are its interfaces , which provides runtime polymorphism . Interfaces are a class of types and provide

1744-469: A more finely grained rule set than basic type checking, but this comes at a price when the type inferences (and other properties) become undecidable , and when more attention must be paid by the programmer to annotate code or to consider computer-related operations and functioning. It is challenging to find a sufficiently expressive type system that satisfies all programming practices in a type safe manner. A programming language compiler can also implement

1853-818: A reference whose static target type (or manifest type) is equal to either the object's run-time type (its latent type) or a supertype thereof. This is conformant with the Liskov substitution principle , which states that all operations performed on an instance of a given type can also be performed on an instance of a subtype. This concept is also known as subsumption or subtype polymorphism . In some languages subtypes may also possess covariant or contravariant return types and argument types respectively. Certain languages, for example Clojure , Common Lisp , or Cython are dynamically type checked by default, but allow programs to opt into static type checking by providing optional annotations. One reason to use such hints would be to optimize

1962-548: A run-time type check. The language constructs to do so are the type assertion , which checks against a single potential type: and the type switch , which checks against multiple types: The empty interface interface {} is an important base case because it can refer to an item of any concrete type. It is similar to the Object class in Java or C# and is satisfied by any type, including built-in types like int . Code using

2071-590: A semicolon; as a side effect of the evaluation, functions may be called and variables assigned new values. To modify the normal sequential execution of statements, C provides several control-flow statements identified by reserved keywords. Structured programming is supported by if ... [ else ] conditional execution and by do ... while , while , and for iterative execution (looping). The for statement has separate initialization, testing, and reinitialization expressions, any or all of which can be omitted. break and continue can be used within

2180-401: A set of types (known as type set) using | (Union) operator, as well as a set of methods. These changes were made to support type constraints in generics code. For a generic function or type, a constraint can be thought of as the type of the type argument: a meta-type. This new ~T syntax will be the first use of ~ as a token in Go. ~T means the set of all types whose underlying type

2289-429: A simple type system is that of the C language . The portions of a C program are the function definitions. One function is invoked by another function. The interface of a function states the name of the function and a list of parameters that are passed to the function's code. The code of an invoking function states the name of the invoked, along with the names of variables that hold values to pass to it. During

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2398-420: A static type checker. The reason for this is that many useful features or properties are difficult or impossible to verify statically. For example, suppose that a program defines two types, A and B, where B is a subtype of A. If the program tries to convert a value of type A to type B, which is known as downcasting , then the operation is legal only if the value being converted is actually a value of type B. Thus,

2507-407: A strict sense. Static type checking is the process of verifying the type safety of a program based on analysis of a program's text ( source code ). If a program passes a static type checker, then the program is guaranteed to satisfy some set of type safety properties for all possible inputs. Static type checking can be considered a limited form of program verification (see type safety ), and in

2616-467: A type checker would not detect. The process of verifying and enforcing the constraints of types— type checking —may occur at compile time (a static check) or at run-time (a dynamic check). If a language specification requires its typing rules strongly, more or less allowing only those automatic type conversions that do not lose information, one can refer to the process as strongly typed; i f not, as weakly typed . The terms are not usually used in

2725-447: A type-safe language, can also be considered an optimization. If a compiler can prove that a program is well-typed, then it does not need to emit dynamic safety checks, allowing the resulting compiled binary to run faster and to be smaller. Static type checking for Turing-complete languages is inherently conservative. That is, if a type system is both sound (meaning that it rejects all incorrect programs) and decidable (meaning that it

2834-436: A type. Even a type can become associated with a type. An implementation of a type system could in theory associate identifications called data type (a type of a value), class (a type of an object), and kind (a type of a type , or metatype). These are the abstractions that typing can go through, on a hierarchy of levels contained in a system. When a programming language evolves a more elaborate type system, it gains

2943-636: A value between any two types that have the same size, effectively subverting the type concept. Dynamic type checking is the process of verifying the type safety of a program at runtime. Implementations of dynamically type-checked languages generally associate each runtime object with a type tag (i.e., a reference to a type) containing its type information. This runtime type information (RTTI) can also be used to implement dynamic dispatch , late binding , downcasting , reflective programming (reflection), and similar features. Most type-safe languages include some form of dynamic type checking, even if they also have

3052-423: A warning message if a local function was called with the wrong number of arguments, or if different calls to an external function used different numbers or types of arguments. Separate tools such as Unix's lint utility were developed that (among other things) could check for consistency of function use across multiple source files. In the years following the publication of K&R C, several features were added to

3161-410: A way to bypass the type checker. Some languages allow programmers to choose between static and dynamic type safety. For example, historically C# declares variables statically, but C# 4.0 introduces the dynamic keyword, which is used to declare variables to be checked dynamically at runtime. Other languages allow writing code that is not type-safe; for example, in C , programmers can freely cast

3270-421: A weakness that might be changed at some point. The Google team built at least one compiler for an experimental Go dialect with generics, but did not release it. In August 2018, the Go principal contributors published draft designs for generic programming and error handling and asked users to submit feedback. However, the error handling proposal was eventually abandoned. In June 2020, a new draft design document

3379-612: A wide variety of mainframe computers , minicomputers , and microcomputers , including the IBM PC , as its popularity began to increase significantly. In 1983 the American National Standards Institute (ANSI) formed a committee, X3J11, to establish a standard specification of C. X3J11 based the C standard on the Unix implementation; however, the non-portable portion of the Unix C library was handed off to

Go (programming language) - Misplaced Pages Continue

3488-404: Is T . Go uses the iota keyword to create enumerated constants. In Go's package system, each package has a path (e.g., "compress/bzip2" or "golang.org/x/net/html" ) and a name (e.g., bzip2 or html ). References to other packages' definitions must always be prefixed with the other package's name, and only the capitalized names from other packages are accessible: io.Reader

3597-506: Is C++ RTTI . More generally, most programming languages include mechanisms for dispatching over different 'kinds' of data, such as disjoint unions , runtime polymorphism , and variant types . Even when not interacting with type annotations or type checking, such mechanisms are materially similar to dynamic typing implementations. See programming language for more discussion of the interactions between static and dynamic typing. Objects in object-oriented languages are usually accessed by

3706-508: Is Go. There are two major implementations: A third-party source-to-source compiler , GopherJS, compiles Go to JavaScript for front-end web development . Go was designed at Google in 2007 to improve programming productivity in an era of multicore , networked machines and large codebases . The designers wanted to address criticisms of other languages in use at Google, but keep their useful characteristics: Its designers were primarily motivated by their shared dislike of C++ . Go

3815-671: Is a statement. In Go, statements are separated by ending a line (hitting the Enter key) or by a semicolon " ; ". Hitting the Enter key adds " ; " to the end of the line implicitly (does not show up in the source code). The left curly bracket { cannot come at the start of a line. Go has a number of built-in types, including numeric ones ( byte , int64 , float32 , etc.), Booleans , and byte strings ( string ). Strings are immutable; built-in operators and keywords (rather than functions) provide concatenation, comparison, and UTF-8 encoding/decoding. Record types can be defined with

3924-456: Is an informal name for the current major C language standard revision. It was informally known as "C2X" through most of its development. C23 was published in October 2024 as ISO/IEC 9899:2024. The standard macro __STDC_VERSION__ is defined as 202311L to indicate that C23 support is available. C2Y is an informal name for the next major C language standard revision, after C23 (C2X), that

4033-504: Is defined as 201112L to indicate that C11 support is available. C17 is an informal name for ISO/IEC 9899:2018, a standard for the C programming language published in June 2018. It introduces no new language features, only technical corrections, and clarifications to defects in C11. The standard macro __STDC_VERSION__ is defined as 201710L to indicate that C17 support is available. C23

4142-524: Is for the most part backward compatible with C90, but is stricter in some ways; in particular, a declaration that lacks a type specifier no longer has int implicitly assumed. A standard macro __STDC_VERSION__ is defined with value 199901L to indicate that C99 support is available. GCC , Solaris Studio , and other C compilers now support many or all of the new features of C99. The C compiler in Microsoft Visual C++ , however, implements

4251-469: Is hoped to be released later in the 2020s decade, hence the '2' in "C2Y". An early working draft of C2Y was released in February 2024 as N3220 by the working group ISO/IEC JTC1/SC22 /WG14. Historically, embedded C programming requires non-standard extensions to the C language to support exotic features such as fixed-point arithmetic , multiple distinct memory banks , and basic I/O operations. In 2008,

4360-427: Is increased. Advocates of dependent typing , implemented in languages such as Dependent ML and Epigram , have suggested that almost all bugs can be considered type errors, if the types used in a program are properly declared by the programmer or correctly inferred by the compiler. Static typing usually results in compiled code that executes faster. When the compiler knows the exact data types that are in use (which

4469-500: Is necessary for static verification, either through declaration or inference) it can produce optimized machine code. Some dynamically typed languages such as Common Lisp allow optional type declarations for optimization for this reason. By contrast, dynamic typing may allow compilers to run faster and interpreters to dynamically load new code, because changes to source code in dynamically typed languages may result in less checking to perform and less code to revisit. This too may reduce

Go (programming language) - Misplaced Pages Continue

4578-430: Is not precisely defined and therefore not wrong, it usually implies that type conformance is not statically checked. Because conformance to a Go interface is checked statically by the Go compiler (except when performing a type assertion), the Go authors prefer the term structural typing . The definition of an interface type lists required methods by name and type. Any object of type T for which functions exist matching all

4687-622: Is now also referred to as C78 . The second edition of the book covers the later ANSI C standard, described below. K&R introduced several language features: Even after the publication of the 1989 ANSI standard, for many years K&R C was still considered the " lowest common denominator " to which C programmers restricted themselves when maximum portability was desired, since many older compilers were still in use, and because carefully written K&R C code can be legal Standard C as well. In early versions of C, only functions that return types other than int must be declared if used before

4796-484: Is one of language's major selling points. Go is influenced by C (especially the Plan 9 dialect ), but with an emphasis on greater simplicity and safety. It consists of: Go's syntax includes changes from C aimed at keeping code concise and readable. A combined declaration/initialization operator was introduced that allows the programmer to write i := 3 or s := "Hello, world!" , without specifying

4905-402: Is possible to write an algorithm that determines whether a program is well-typed), then it must be incomplete (meaning there are correct programs, which are also rejected, even though they do not encounter runtime errors). For example, consider a program containing the code: Even if the expression <complex test> always evaluates to true at run-time, most type checkers will reject

5014-713: Is possible with static typing, but requires advanced uses of algebraic data types . Further, dynamic typing better accommodates transitional code and prototyping, such as allowing a placeholder data structure ( mock object ) to be transparently used in place of a full data structure (usually for the purposes of experimentation and testing). Dynamic typing typically allows duck typing (which enables easier code reuse ). Many languages with static typing also feature duck typing or other mechanisms like generic programming that also enable easier code reuse. Dynamic typing typically makes metaprogramming easier to use. For example, C++ templates are typically more cumbersome to write than

5123-443: Is public but bzip2.reader is not. The go get command can retrieve packages stored in a remote repository and developers are encouraged to develop packages inside a base path corresponding to a source repository (such as example.com/user_name/package_name) to reduce the likelihood of name collision with future additions to the standard library or other external libraries. Static typing Type systems formalize and enforce

5232-420: Is sometimes called C90. Therefore, the terms "C89" and "C90" refer to the same programming language. ANSI, like other national standards bodies, no longer develops the C standard independently, but defers to the international C standard, maintained by the working group ISO/IEC JTC1/SC22 /WG14. National adoption of an update to the international standard typically occurs within a year of ISO publication. One of

5341-489: The struct keyword. For each type T and each non-negative integer constant n , there is an array type denoted [ n ] T ; arrays of differing lengths are thus of different types. Dynamic arrays are available as "slices", denoted [] T for some type T . These have a length and a capacity specifying when new memory needs to be allocated to expand the array. Several slices may share their underlying memory. Pointers are available for all types, and

5450-487: The uint32 value x as an IP address. Simply assigning x to a variable of type ipv4addr is a type error. Constant expressions may be either typed or "untyped"; they are given a type when assigned to a typed variable if the value they represent passes a compile-time check. Function types are indicated by the func keyword; they take zero or more parameters and return zero or more values, all of which are typed. The parameter and return values determine

5559-597: The IEEE working group 1003 to become the basis for the 1988 POSIX standard. In 1989, the C standard was ratified as ANSI X3.159-1989 "Programming Language C". This version of the language is often referred to as ANSI C , Standard C, or sometimes C89. In 1990 the ANSI C standard (with formatting changes) was adopted by the International Organization for Standardization (ISO) as ISO/IEC 9899:1990, which

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5668-483: The C Standards Committee published a technical report extending the C language to address these issues by providing a common standard for all implementations to adhere to. It includes a number of features not available in normal C, such as fixed-point arithmetic, named address spaces, and basic I/O hardware addressing. C has a formal grammar specified by the C standard. Line endings are generally not significant in C; however, line boundaries do have significance during

5777-597: The C89 standard and those parts of C99 that are required for compatibility with C++11 . In addition, the C99 standard requires support for identifiers using Unicode in the form of escaped characters (e.g. \u0040 or \U0001f431 ) and suggests support for raw Unicode names. Work began in 2007 on another revision of the C standard, informally called "C1X" until its official publication of ISO/IEC 9899:2011 on December 8, 2011. The C standards committee adopted guidelines to limit

5886-510: The Go project. Go is a humanist sans-serif resembling Lucida Grande , and Go Mono is monospaced . Both fonts adhere to the WGL4 character set and were designed to be legible with a large x-height and distinct letterforms . Both Go and Go Mono adhere to the DIN 1450 standard by having a slashed zero, lowercase l with a tail, and an uppercase I with serifs. In April 2018, the original logo

5995-444: The ability to be generic using type parameters. These type parameters are specified within square brackets, right after the function or type name. The compiler transforms the generic function or type into non-generic by substituting type arguments for the type parameters provided, either explicitly by the user or type inference by the compiler. This transformation process is referred to as type instantiation. Interfaces now can define

6104-531: The address of the first item in the array. Pass-by-reference is simulated in C by explicitly passing pointers to the thing being referenced. C program source text is free-form code. Semicolons terminate statements , while curly braces are used to group statements into blocks . The C language also exhibits the following characteristics: While C does not include certain features found in other languages (such as object orientation and garbage collection ), these can be implemented or emulated, often through

6213-438: The adoption of new features that had not been tested by existing implementations. The C11 standard adds numerous new features to C and the library, including type generic macros, anonymous structures, improved Unicode support, atomic operations, multi-threading, and bounds-checked functions. It also makes some portions of the existing C99 library optional, and improves compatibility with C++. The standard macro __STDC_VERSION__

6322-428: The aims of the C standardization process was to produce a superset of K&R C, incorporating many of the subsequently introduced unofficial features. The standards committee also included several additional features such as function prototypes (borrowed from C++), void pointers, support for international character sets and locales , and preprocessor enhancements. Although the syntax for parameter declarations

6431-416: The basis for several implementations of C on new platforms. In 1978 Brian Kernighan and Dennis Ritchie published the first edition of The C Programming Language . Known as K&R from the initials of its authors, the book served for many years as an informal specification of the language. The version of C that it describes is commonly referred to as " K&R C ". As this was released in 1978, it

6540-418: The capabilities of the targeted CPUs. It has found lasting use in operating systems code (especially in kernels ), device drivers , and protocol stacks , but its use in application software has been decreasing. C is commonly used on computer architectures that range from the largest supercomputers to the smallest microcontrollers and embedded systems . A successor to the programming language B , C

6649-445: The combination of all places where values are created and all places where a certain value is used must be taken into account. A number of useful and common programming language features cannot be checked statically, such as downcasting . Thus, many languages will have both static and dynamic type checking; the static type checker verifies what it can, and dynamic checks verify the rest. Many languages with static type checking provide

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6758-399: The compiler or specified by a programmer, a type system renders program behavior illegal if it falls outside the type-system rules. Advantages provided by programmer-specified type systems include: Advantages provided by compiler-specified type systems include: A type error occurs when an operation receives a different type of data than it expected. For example, a type error would happen if

6867-468: The cost of making the type checking itself an undecidable problem (as in the Halting problem ). In a type system with automated type checking, a program may prove to run incorrectly yet produce no compiler errors. Division by zero is an unsafe and incorrect operation, but a type checker which only runs at compile time does not scan for division by zero in most languages; that division would surface as

6976-411: The differences between type systems that lead people to call them "strong" or "weak". C (programming language) This is an accepted version of this page C ( pronounced / ˈ s iː / – like the letter c ) is a general-purpose programming language . It was created in the 1970s by Dennis Ritchie and remains very widely used and influential. By design, C's features cleanly reflect

7085-427: The edit-compile-test-debug cycle. Statically typed languages that lack type inference (such as C and Java prior to version 10 ) require that programmers declare the types that a method or function must use. This can serve as added program documentation, that is active and dynamic, instead of static. This allows a compiler to prevent it from drifting out of synchrony, and from being ignored by programmers. However,

7194-453: The effect of creating a combined interface that is satisfied by exactly the types that implement the embedded interface and any methods that the newly defined interface adds. The Go standard library uses interfaces to provide genericity in several places, including the input/output system that is based on the concepts of Reader and Writer . Besides calling methods via interfaces, Go allows converting interface values to other types with

7303-598: The empty interface cannot simply call methods (or built-in operators) on the referred-to object, but it can store the interface {} value, try to convert it to a more useful type via a type assertion or type switch, or inspect it with Go's reflect package. Because interface {} can refer to any value, it is a limited way to escape the restrictions of static typing, like void * in C but with additional run-time type checks. The interface {} type can be used to model structured data of any arbitrary schema in Go, such as JSON or YAML data, by representing it as

7412-468: The equivalent Ruby or Python code since C++ has stronger rules regarding type definitions (for both functions and variables). This forces a developer to write more boilerplate code for a template than a Python developer would need to. More advanced run-time constructs such as metaclasses and introspection are often harder to use in statically typed languages. In some languages, such features may also be used e.g. to generate new types and behaviors on

7521-650: The features of the more-powerful PDP-11. A significant addition was a character data type. He called this New B (NB). Thompson started to use NB to write the Unix kernel, and his requirements shaped the direction of the language development. Through to 1972, richer types were added to the NB language: NB had arrays of int and char . Pointers, the ability to generate pointers to other types, arrays of all types, and types to be returned from functions were all also added. Arrays within expressions became pointers. A new compiler

7630-450: The fly, based on run-time data. Such advanced constructs are often provided by dynamic programming languages ; many of these are dynamically typed, although dynamic typing need not be related to dynamic programming languages . Languages are often colloquially referred to as strongly typed or weakly typed . In fact, there is no universally accepted definition of what these terms mean. In general, there are more precise terms to represent

7739-477: The function definition; functions used without prior declaration were presumed to return type int . For example: The int type specifiers which are commented out could be omitted in K&;R C, but are required in later standards. Since K&R function declarations did not include any information about function arguments, function parameter type checks were not performed, although some compilers would issue

7848-404: The invoked function. The C compiler checks the types of the arguments passed to a function when it is called against the types of the parameters declared in the function's definition. If the types do not match, the compiler throws a compile-time error or warning. A compiler may also use the static type of a value to optimize the storage it needs and the choice of algorithms for operations on

7957-518: The language's original type syntax and grammar . The main purpose of a type system in a programming language is to reduce possibilities for bugs in computer programs due to type errors . The given type system in question determines what constitutes a type error, but in general, the aim is to prevent operations expecting a certain kind of value from being used with values of which that operation does not make sense (validity errors). Type systems allow defining interfaces between different parts of

8066-438: The language, supported by compilers from AT&T (in particular PCC ) and some other vendors. These included: The large number of extensions and lack of agreement on a standard library , together with the language popularity and the fact that not even the Unix compilers precisely implemented the K&R specification, led to the necessity of standardization. During the late 1970s and 1980s, versions of C were implemented for

8175-414: The language, with special syntax and built-in functions. chan T is a channel that allows sending values of type T between concurrent Go processes . Aside from its support for interfaces , Go's type system is nominal : the type keyword can be used to define a new named type , which is distinct from other named types that have the same layout (in the case of a struct , the same members in

8284-457: The language. A programming language may further associate an operation with various resolutions for each type, in the case of type polymorphism . Type theory is the study of type systems. The concrete types of some programming languages, such as integers and strings, depend on practical issues of computer architecture , compiler implementation, and language design . Formally, type theory studies type systems. A programming language must have

8393-413: The loop. Break is used to leave the innermost enclosing loop statement and continue is used to skip to its reinitialisation. There is also a non-structured goto statement which branches directly to the designated label within the function. switch selects a case to be executed based on the value of an integer expression. Different from many other languages, control-flow will fall through to

8502-411: The next case unless terminated by a break . Expressions can use a variety of built-in operators and may contain function calls. The order in which arguments to functions and operands to most operators are evaluated is unspecified. The evaluations may even be interleaved. However, all side effects (including storage to variables) will occur before the next " sequence point "; sequence points include

8611-419: The operating system to a PDP-11 . The original PDP-11 version of Unix was also developed in assembly language. Thompson wanted a programming language for developing utilities for the new platform. He first tried writing a Fortran compiler, but he soon gave up the idea and instead created a cut-down version of the recently developed systems programming language called BCPL . The official description of BCPL

8720-452: The opportunity to type check using the type system whether at compile time or runtime, manually annotated or automatically inferred. As Mark Manasse concisely put it: The fundamental problem addressed by a type theory is to ensure that programs have meaning. The fundamental problem caused by a type theory is that meaningful programs may not have meanings ascribed to them. The quest for richer type systems results from this tension. Assigning

8829-567: The original language designer, served for many years as the de facto standard for the language. C has been standardized since 1989 by the American National Standards Institute (ANSI) and, subsequently, jointly by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). C is an imperative procedural language, supporting structured programming , lexical variable scope , and recursion , with

8938-413: The otherwise implicit categories the programmer uses for algebraic data types , data structures , or other data types , such as "string", "array of float", "function returning boolean". Type systems are often specified as part of programming languages and built into interpreters and compilers , although the type system of a language can be extended by optional tools that perform added checks using

9047-502: The performance of critical sections of a program. This is formalized by gradual typing . The programming environment DrRacket , a pedagogic environment based on Lisp, and a precursor of the language Racket is also soft-typed. Conversely, as of version 4.0, the C# language provides a way to indicate that a variable should not be statically type checked. A variable whose type is dynamic will not be subject to static type checking. Instead,

9156-590: The pointer-to- T type is denoted * T . Address-taking and indirection use the & and * operators, as in C, or happen implicitly through the method call or attribute access syntax. There is no pointer arithmetic, except via the special unsafe.Pointer type in the standard library. For a pair of types K , V , the type map[ K ] V is the type mapping type- K keys to type- V values, though Go Programming Language specification does not give any performance guarantees or implementation requirements for map types. Hash tables are built into

9265-485: The possible values that a sequence of bits might mean . Associating a sequence of bits with a type conveys that meaning to the programmable hardware to form a symbolic system composed of that hardware and some program. A program associates each value with at least one specific type, but it also can occur that one value is associated with many subtypes . Other entities, such as objects , modules , communication channels , and dependencies can become associated with

9374-652: The preprocessing phase. Comments may appear either between the delimiters /* and */ , or (since C99) following // until the end of the line. Comments delimited by /* and */ do not nest, and these sequences of characters are not interpreted as comment delimiters if they appear inside string or character literals. C source files contain declarations and function definitions. Function definitions, in turn, contain declarations and statements . Declarations either define new types using keywords such as struct , union , and enum , or assign types to and perhaps reserve storage for new variables, usually by writing

9483-415: The program as ill-typed, because it is difficult (if not impossible) for a static analyzer to determine that the else branch will not be taken. Consequently, a static type checker will quickly detect type errors in rarely used code paths. Without static type checking, even code coverage tests with 100% coverage may be unable to find such type errors. The tests may fail to detect such type errors, because

9592-502: The program relies on runtime type information to determine how the variable may be used. In Rust , the dyn std :: any :: Any type provides dynamic typing of ' static types. The choice between static and dynamic typing requires certain trade-offs . Static typing can find type errors reliably at compile time, which increases the reliability of the delivered program. However, programmers disagree over how commonly type errors occur, resulting in further disagreements over

9701-409: The proportion of those bugs that are coded that would be caught by appropriately representing the designed types in code. Static typing advocates believe programs are more reliable when they have been well type-checked, whereas dynamic-typing advocates point to distributed code that has proven reliable and to small bug databases. The value of static typing increases as the strength of the type system

9810-408: The recognizable expression and statement syntax of C with underlying type systems, data models, and semantics that can be radically different. The origin of C is closely tied to the development of the Unix operating system, originally implemented in assembly language on a PDP-7 by Dennis Ritchie and Ken Thompson , incorporating several ideas from colleagues. Eventually, they decided to port

9919-461: The required methods of interface type I is an object of type I as well. The definition of type T need not (and cannot) identify type I. For example, if Shape , Square and Circle are defined as then both a Square and a Circle are implicitly a Shape and can be assigned to a Shape -typed variable. In formal language, Go's interface system provides structural rather than nominal typing. Interfaces can embed other interfaces with

10028-420: The same order). Some conversions between types (e.g., between the various integer types) are pre-defined and adding a new type may define additional conversions, but conversions between named types must always be invoked explicitly. For example, the type keyword can be used to define a type for IPv4 addresses, based on 32-bit unsigned integers as follows: With this type definition, ipv4addr(x) interprets

10137-408: The standard library. All versions up through the current Go 1.23 release have maintained this promise. Go does not follow SemVer ; rather, each major Go release is supported until there are two newer major releases. Unlike most software, Go calls the second number in a version the major, i.e., in 1.x x is the major version. This is because Go plans to never reach 2.0, given that compatibility

10246-537: The top four languages in the TIOBE index , a measure of the popularity of programming languages. C is an imperative , procedural language in the ALGOL tradition. It has a static type system . In C, all executable code is contained within subroutines (also called "functions", though not in the sense of functional programming ). Function parameters are passed by value, although arrays are passed as pointers , i.e.

10355-468: The type followed by the variable name. Keywords such as char and int specify built-in types. Sections of code are enclosed in braces ( { and } , sometimes called "curly brackets") to limit the scope of declarations and to act as a single statement for control structures. As an imperative language, C uses statements to specify actions. The most common statement is an expression statement , consisting of an expression to be evaluated, followed by

10464-675: The types of variables used. This contrasts with C's int i = 3 ; and const char * s = "Hello, world!" ; . Semicolons still terminate statements; but are implicit when the end of a line occurs. Methods may return multiple values, and returning a result , err pair is the conventional way a method indicates an error to its caller in Go. Go adds literal syntaxes for initializing struct parameters by name and for initializing maps and slices . As an alternative to C's three-statement for loop, Go's range expressions allow concise iteration over arrays, slices, strings, maps, and channels. fmt.Println("Hello World!")

10573-476: The urging of Alan Snyder and also in recognition of the usefulness of the file-inclusion mechanisms available in BCPL and PL/I . Its original version provided only included files and simple string replacements: #include and #define of parameterless macros. Soon after that, it was extended, mostly by Mike Lesk and then by John Reiser, to incorporate macros with arguments and conditional compilation . Unix

10682-715: The use of external libraries (e.g., the GLib Object System or the Boehm garbage collector ). Many later languages have borrowed directly or indirectly from C, including C++ , C# , Unix's C shell , D , Go , Java , JavaScript (including transpilers ), Julia , Limbo , LPC , Objective-C , Perl , PHP , Python , Ruby , Rust , Swift , Verilog and SystemVerilog (hardware description languages). These languages have drawn many of their control structures and other basic features from C. Most of them also express highly similar syntax to C, and they tend to combine

10791-541: The use on a K&R C-based compiler of features available only in Standard C. After the ANSI/ISO standardization process, the C language specification remained relatively static for several years. In 1995, Normative Amendment 1 to the 1990 C standard (ISO/IEC 9899/AMD1:1995, known informally as C95) was published, to correct some details and to add more extensive support for international character sets. The C standard

10900-410: The value. In many C compilers the float data type , for example, is represented in 32 bits , in accord with the IEEE specification for single-precision floating point numbers . They will thus use floating-point-specific microprocessor operations on those values (floating-point addition, multiplication, etc.). The depth of type constraints and the manner of their evaluation affect the typing of

11009-513: Was augmented to include the style used in C++, the K&R interface continued to be permitted, for compatibility with existing source code. C89 is supported by current C compilers, and most modern C code is based on it. Any program written only in Standard C and without any hardware-dependent assumptions will run correctly on any platform with a conforming C implementation, within its resource limits. Without such precautions, programs may compile only on

11118-706: Was further revised in the late 1990s, leading to the publication of ISO/IEC 9899:1999 in 1999, which is commonly referred to as " C99 ". It has since been amended three times by Technical Corrigenda. C99 introduced several new features, including inline functions , several new data types (including long long int and a complex type to represent complex numbers ), variable-length arrays and flexible array members , improved support for IEEE 754 floating point, support for variadic macros (macros of variable arity ), and support for one-line comments beginning with // , as in BCPL or C++. Many of these had already been implemented as extensions in several C compilers. C99

11227-511: Was not available at the time, and Thompson modified the syntax to be less 'wordy' and similar to a simplified ALGOL known as SMALGOL. He called the result B , describing it as "BCPL semantics with a lot of SMALGOL syntax". Like BCPL, B had a bootstrapping compiler to facilitate porting to new machines. Ultimately, few utilities were written in B because it was too slow and could not take advantage of PDP-11 features such as byte addressability. In 1971 Ritchie started to improve B, to use

11336-628: Was one of the first operating system kernels implemented in a language other than assembly . Earlier instances include the Multics system (which was written in PL/I ) and Master Control Program (MCP) for the Burroughs B5000 (which was written in ALGOL ) in 1961. In around 1977, Ritchie and Stephen C. Johnson made further changes to the language to facilitate portability of the Unix operating system. Johnson's Portable C Compiler served as

11445-466: Was originally developed at Bell Labs by Ritchie between 1972 and 1973 to construct utilities running on Unix . It was applied to re-implementing the kernel of the Unix operating system. During the 1980s, C gradually gained popularity. It has become one of the most widely used programming languages, with C compilers available for practically all modern computer architectures and operating systems. The book The C Programming Language , co-authored by

11554-596: Was publicly announced in November 2009, and version 1.0 was released in March 2012. Go is widely used in production at Google and in many other organizations and open-source projects. The Gopher mascot was introduced in 2009 for the open source launch of the language. The design, by Renée French , borrowed from a c. 2000 WFMU promotion. In November 2016, the Go and Go Mono fonts were released by type designers Charles Bigelow and Kris Holmes specifically for use by

11663-406: Was published that would add the necessary syntax to Go for declaring generic functions and types. A code translation tool, go2go , was provided to allow users to try the new syntax, along with a generics-enabled version of the online Go Playground. Generics were finally added to Go in version 1.18 on March 15, 2022. Go 1 guarantees compatibility for the language specification and major parts of

11772-439: Was redesigned by brand designer Adam Smith. The new logo is a modern, stylized GO slanting right with trailing streamlines. (The Gopher mascot remained the same.) The lack of support for generic programming in initial versions of Go drew considerable criticism. The designers expressed an openness to generic programming and noted that built-in functions were in fact type-generic, but are treated as special cases; Pike called this

11881-474: Was written, and the language was renamed C. The C compiler and some utilities made with it were included in Version 2 Unix , which is also known as Research Unix . At Version 4 Unix , released in November 1973, the Unix kernel was extensively re-implemented in C. By this time, the C language had acquired some powerful features such as struct types. The preprocessor was introduced around 1973 at

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