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Encyclopedia > Datatype

In computer science, a datatype or data type (often simply a type) is a name or label for a set of values and some operations which one can perform on that set of values. Programming languages implicitly or explicitly support one or more datatypes; these types may act as a statically or dynamically checked constraint, ensuring valid programs for a given language. Computer science is the study of information and computation. ... Computer code (HTML with JavaScript) in a tool that uses syntax highlighting (colors) to help the developer see the function of each piece of code. ... A constraint is a limitation of possibilities. ... A computer program or software program (usually abbreviated to a program) is a step-by-step list of instructions written for a particular computer architecture in a particular computer programming language. ...

Contents


Basis

Assigning datatypes ("typing") has the basic purpose of giving some semantic meaning to otherwise meaningless collections of bits. Types usually have associations either with values in memory or with objects such as variables. Because any value simply consists of a set of bits in a computer, hardware makes no distinction even between memory addresses, instruction code, characters, integers and floating-point numbers. Types inform programs and programmers how they should treat those mere bits. In general, semantics (from the Greek semantikos, or significant meaning, derived from sema, sign) is the study of meaning, in some sense of that term. ... This article is about the unit of information. ... The terms storage (U.K.) or memory (U.S.) refer to the parts of a digital computer that retain physical state (data) for some interval of time, possibly even after electrical power to the computer is turned off. ... In strictly mathematical branches of computer science the term object is used in a purely mathematical sense to refer to any thing. While this interpretation is useful in the discussion of abstract theory, it is not concrete enough to serve as a primitive datatype in the discussion of more concrete... In computer science and mathematics, a variable is a symbol denoting a quantity or symbolic representation. ... A computer is a machine capable of undergoing complex calculations. ... In computer science, a memory address is a unique identifier for a memory location at which a CPU or other device can store a piece of data for later retrieval. ... A computer can perform operations, each of which is assigned a numeric code called an opcode. ... The integers consist of the positive natural numbers (1, 2, 3, …), their negatives (−1, −2, −3, ...) and the number zero. ... A floating-point number is a digital representation for a number in a certain subset of the rational numbers, and is often used to approximate an arbitrary real number on a computer. ...


Major functions that type systems provide include:

  • Safety - Use of types may allow a compiler to detect meaningless or provably invalid code. For example, we can identify an expression "Hello, World" / 3 as invalid because one cannot divide (in the usual sense) a string literal by an integer. As discussed below, strong typing offers more safety, but it does not necessarily guarantee complete safety (see type-safety for more information).
  • Optimization - Static type-checking may provide useful information to a compiler. For example, if a type says a value must align at a multiple of 4, the compiler may be able to use more efficient machine instructions.
  • Documentation - In more expressive type systems, types can serve as a form of documentation, since they can illustrate the intent of the programmer. For instance, timestamps may be a subtype of integers -- but if a programmer declares a function as returning a timestamp rather than merely an integer, this documents part of the meaning of the function.
  • Abstraction (or modularity) - Types allow programmers to think about programs at a higher level, not bothering with low-level implementation. For example, programmers can think of strings as values instead of as a mere array of bytes. Or types can allow programmers to express the interface between two subsystems. This localizes the definitions required for interoperability of the subsystems and prevents inconsistencies when those subsystems communicate.

Typically a program associates each value with one particular type (although a type may have more than one subtype). Other entities, such as objects, modules, communication channels, dependencies, or even types themselves, can become associated with a type. For example: A diagram of the operation of a typical multi-language compiler. ... In various branches of mathematics and computer science, strings are sequences of various simple objects (symbols, tokens, characters, etc. ... The integers consist of the positive natural numbers (1, 2, 3, …), their negatives (−1, −2, −3, ...) and the number zero. ... This article or section contains information that has not been verified and thus might not be reliable. ... In general terms, documentation is any communicable material (such as text, video, audio, etc. ... ... WordNet gives four main senses for the English noun object: a physical entity; something that is within the grasp of the senses; an aim, target or objective — see Object (task); a grammatical Object — either a direct object or an indirect object the focus of cognitions or feelings. ... A module is a self-contained component of a system, which has a well-defined interface to the other components; something is modular if it is constructed so as to facilitate easy assembly, flexible arrangement, and/or repair of the components. ... In computer science, dependency or coupling is the degree to which each program module relies on each other module. ...

  • datatype - a type of a value
  • class - a type of an object
  • kind - a type of a type

A type system, specified in each programming language, stipulates the ways typed programs may behave and makes behavior outside these rules illegal. An effect system typically provides more fine-grained control than a type system. In object-oriented programming, classes are used to group related variables and functions. ... Kind can mean: Hundreds Bankekind Hundred - a hundred of Ostrogothia in Sweden Frökind Hundred - a hundred of Westrogothia in Sweden Hammarkind Hundred - a hundred of Ostrogothia in Sweden Hanekind Hundred - a hundred of Ostrogothia in Sweden Kind Hundred - a hundred divided between Hallandia, Smalandia and Westrogothia in Sweden Kinda... An effect system is a formal system which describes the computational effects of computer programs, such as side effects. ...


More formally, type theory studies type systems. At the broadest level, type theory is the branch of mathematics and logic that concerns itself with classifying entities into collections called types. ...


Type checking

The process of verifying and enforcing the constraints of types - type checking - may occur either at compile-time (a static check) or run-time (a dynamic check). Static type-checking becomes a primary task of the semantic analysis carried out by a compiler. If a language enforces type rules strongly (that is, generally allowing only those automatic type conversions which do not lose information), one can refer to the process as strongly typed, if not, as weakly typed. In computer science, compile time, as opposed to runtime, is the time when a compiler compiles code written in a programming language into an executable form. ... In computer science, runtime describes the operation of a computer program, the duration of its execution, from beginning to termination (compare compile time). ... In computer science, semantic analysis is a pass by a compiler that adds semantical information to the parse tree and performs certain checks based on this information. ... A diagram of the operation of a typical multi-language compiler. ...


Static and dynamic typing

In dynamic typing, type checking often takes place at runtime because variables can acquire different types depending on the execution path. Static type systems for dynamic types usually need to explicitly represent the concept of an execution path, and allow types to depend on it. This seems to require either a trivial or a cumbersome type system in order to work well. In computer science, run time (with a space, though often its spelled without one) describes the operation of a computer program, the duration of its execution, from beginning to termination (compare compile time). ...


Dynamic typing often occurs in "scripting languages" and other rapid application development languages. Dynamic types are more often encountered in interpreted languages, whereas compiled languages favour static types. See typed and untyped languages for a fuller list of typed and untyped languages. Scripting languages (commonly called scripting programming languages or script languages) are computer programming languages initially designed for scripting the operations of a computer. ... Rapid application development (RAD), is a software development process developed initially by James Martin in the 1980s. ... In computer programming, an interpreted language is a programming language whose programs may be executed from source form, by an interpreter. ... A compiled language is a programming language whose implementations are typically compilers (translators which generate machine code from source code), and not interpreters (step-by-step executors of source code, where no translation takes place). ... The factual accuracy of this article is disputed. ...


The term duck typing refers to a form of dynamic typing implemented in languages which "guess" the type of a value. In computer science, duck typing is a term for the dynamic type system typical of some programming languages, such as with Smalltalk, where the variable value itself determines what it can do. ...



To see how type checking works, consider the following pseudocode example: Pseudocode (i. ...

 var x; // (1) x := 5; // (2) x := "hi"; // (3) 

In this example, (1) declares the name x; (2) associates the integer value 5 to the name x; and (3) associates the string value "hi" to the name x. In most statically typed systems, this code fragment would be illegal, because (2) and (3) bind x to values of inconsistent type. The integers consist of the positive natural numbers (1, 2, 3, …), their negatives (−1, −2, −3, ...) and the number zero. ... In computer programming and some branches of mathematics, strings are sequences of various simple objects. ...


By contrast, a purely dynamically typed system would permit the above program to execute, because the name x would not have to have a consistent type. The implementation of a dynamically typed language will catch errors related to the misuse of values - "type errors" - at the time of the computation of the erroneous statement or expression. In other words, dynamic typing catches errors during program execution. A typical implementation of dynamic typing will keep all program values "tagged" with a type, and check the type tag before using any value in an operation. For example: An expression in the very basic sense is the noun form of the verb express. ...

 var x = 5; // (1) var y = "hi"; // (2) var z = x + y; // (3) 

In this code fragment, (1) binds the value 5 to x; (2) binds the value "hi" to y; and (3) attempts to add x to y. In a dynamically typed language, the value bound to x might be a pair (integer, 5), and the value bound to y might be a pair (string, "hi"). When the program attempts to execute line 3, the language implementation would check the type tags integer and string, discover that the operation + (addition) is not defined over these two types, and signals an error. In computer science, the term integer is used to refer to any data type which can represent some subset of the mathematical integers. ... In various branches of mathematics and computer science, strings are sequences of various simple objects (symbols, tokens, characters, etc. ...


Some statically typed languages have a "back door" in the language that enables programmers to write code that does not statically type check. For example, Java and C-style languages have "casts". This article needs cleanup. ...


The presence of static typing in a programming language does not necessarily imply the absence of dynamic typing mechanisms. For example, Java uses static typing, but certain operations require the support of runtime type tests, which are a form of dynamic typing. See programming language for more discussion of the interactions between static and dynamic typing. Computer code (HTML with JavaScript) in a tool that uses syntax highlighting (colors) to help the developer see the function of each piece of code. ...


Type "Tags"

Some dynamic languages use internal "tags" to track how a declaration happens, and some don't, relying on the value itself as the sole indicator of content. For example:

 a = "52"; b = 52; 

In "tag-free" languages, the contents of variable "a" and "b" would be identical. In tagged dynamic languages, internally the variables would carry an internal flag(s) to indicte the type. If we could "X-ray" the variable storage inside a language "engine", we would see something resembling:

 Tagged Types: a: ["52", type: string] b: ["52", type: number] 
 Untagged Types: a: ["52"] b: ["52"] 

In untagged languages, operator overloading is not very effective and more explicit operators are needed. For example, string concatenation may use an ampersand or period instead of a plus sign to avoid ambiguity. Some prefer this approach, saying "what you see is what you get". Which approach is favored is highly debated and seems to be a personal preference. In computer programming, operator overloading (less commonly known as operator ad-hoc polymorphism) is a specific case of polymorphism in which some or all of operators like +, = or == are treated as polymorphic functions and as such have different behaviours depending on the types of their arguments. ...


Tagged dynamic languages usually have a standard operation or set of operations that return the "type" of a given variable. Such a function may be called "typeOf", "typeName", "type", "getType", etc. Non-tagged languages cannot have such (although they may have parsing-based validation operations such as "isNumber"). Some languages are partially tagged in that scalar types are not tracked, but the difference between compound types, such as arrays, and scalars is. It is possible to make this distinction blurred and/or automatic also, but in practice very few languages use such an approach.


Using the tagged approach, types are checked by seeing that a variable or value has the appropriate tag. In some languages a math operation, for example, may refuse to compute with a value having a "string" type since it expects only numbers. Other languages will attempt to convert any string parameters encountered into a number by parsing the string and copying it into a temporary number. Non-tagged languages will always have to parse and validate to do such operations.


Static and dynamic type checking in practice

The choice between static and dynamic typing requires some trade-offs. Many programmers strongly favor one over the other; some to the point of considering languages following the disfavored system to be unusable or crippled. A Tradeoff usually refers to losing one quality or aspect of something in return for gaining another quality or aspect. ...


Static typing finds type errors reliably and at compile time. This should increase the reliability of the delivered program. However, programmers disagree over how commonly type errors occur, and thus what proportion of those bugs which are written would be caught by static typing. Static typing advocates believe programs are more reliable when they have been type-checked, while dynamic typing advocates point to distributed code that has proven reliable and to small bug databases. The value of static typing, then, presumably increases as the strength of the type system is increased. Advocates of strongly typed languages such as ML and Haskell have suggested that almost all bugs can be considered type errors, if the types used in a program are sufficiently well declared by the programmer or inferred by the compiler. ML is a general-purpose functional programming language developed by Robin Milner and others in the late 1970s at the University of Edinburgh, whose syntax is inspired by ISWIM. Historically, ML stands for metalanguage as it was conceived to develop proof tactics in the LCF theorem prover (the language of... Haskell logo Haskell is a standardized pure functional programming language with non-strict semantics named after the logician Haskell Curry. ...


Static typing usually results in compiled code that executes more quickly. When the compiler knows the exact data types that are in use, it can produce machine code that just does the right thing. Further, compilers in statically typed languages can find shortcuts more easily. Some dynamically-typed languages such as Common Lisp allow optional type declarations for optimization for this very reason. Static typing makes this pervasive. See optimization. Common Lisp, commonly abbreviated CL, is a dialect of the Lisp programming language, standardised by ANSI X3. ... In computing, optimization is the process of modifying a system to improve its efficiency. ...


Statically-typed languages which lack type inference – such as Java – require that programmers declare the types they intend a method or function to use. This can serve as additional documentation for the program, which the compiler will not permit the programmer to ignore or drift out of synchronization. However, a language can be statically typed without requiring type declarations, so this is not a consequence of static typing.


Static typing allows construction of libraries which are less likely to be accidentally misused by their users. This can be used as an additional mechanism for communicating the intentions of the library developer.


Dynamic typing allows constructs that some static type systems would reject as illegal. For example, eval functions, which execute arbitrary data as code, become possible (however, the typing within that evaluated code might remain static). Furthermore, dynamic typing accommodates transitional code and prototyping, such as allowing a string to be used in place of a data structure.


Dynamic typing allows debuggers to be more functional; in particular, the debugger can modify the code arbitrarily and let the program continue to run. Programmers in dynamic languages sometimes "program in the debugger" and thus have a shorter edit-compile-test-debug cycle. However, the need to use debuggers is considered by some to be a sign of design or development process problems. A debugger is a computer program that is used to debug (and sometimes test or optimize) other programs which might be running on the same computer (host computer) as the debugger is running, or running on a second remote computer which might be a similar machine, a dissimilar computer, or...


Dynamic typing may allow compilers and interpreters to run more quickly, since there may be less checking to perform and less code to revisit when the source code changes. This, too, may reduce the edit-compile-test-debug cycle.


Strong and weak typing

Main article: strongly-typed programming language The specification of nearly every high level computer programming language includes the concept of type. ...


For a more complete discussion of the different meanings of the phrase strongly typed, see strongly-typed programming language. The specification of nearly every high level computer programming language includes the concept of type. ...


One definition of strongly typed involves not allowing an operation to succeed on arguments which have the wrong type. A C cast gone wrong exemplifies the absence of strong typing; if a programmer casts a value in C, not only must the compiler allow the code, but the runtime should allow it as well. This allows compact and fast C code, but it can make debugging more difficult. The C Programming Language, Brian Kernighan and Dennis Ritchie, the original edition that served for many years as an informal specification of the language The C programming language is a standardized imperative computer programming language developed in the early 1970s by Dennis Ritchie for use on the Unix operating system. ... This article needs cleanup. ... Debugging is a methodical process of finding and reducing the number of bugs, or defects, in a computer program or a piece of electronic hardware thus making it behave as expected. ...


Some pundits use the term memory-safe language (or just safe language) to describe languages that do not allow undefined operations to occur. For example, a memory-safe language will also check array bounds. In computer programming, bounds checking is the name given to any method of detecting whether or not an index given lies within the limits of an array. ...


Weak typing means that a language will implicitly convert (or cast) types when used. Revisiting the previous example:

 var x = 5; // (1) var y = "hi"; // (2) x + y; // (3) 

Writing the code above in a weakly-typed language, such as older versions of Visual Basic (pre-.Net), would produce runnable code which would yield the result "5hi". The system would convert the number 5 into the string "5" to make sense of the operation (the language overloads the plus-sign operator '+' to express both addition and concatenation). However, problems can ensue with such conversions and with operators overloaded in this way. For example, would the following code produce a result of 9 or "54"? Visual Basic (VB) is an event driven programming language and associated development environment, created by Microsoft. ... The . ... In computer science, polymorphism is the idea of allowing the same code to be used with different classes of data (which classes in typed languages correspond to types), resulting in more general and abstract implementations. ... 3 + 2 with apples, a popular choice in textbooks Addition is the most basic operation of arithmetic. ... In formal language theory (and therefore in programming languages), concatenation is the operation of joining two character strings end to end. ...

 var x = 5; var y = "4"; x + y; 


In contrast, the REXX language (a weakly-typed environment because it only has one type) does not overload the '+' operator, and hence '+' always denotes addition. The equivalent of the first example would fail (with one operand not a number), and the second would yield "9", unambiguously. Careful language design has also allowed other languages to appear weakly-typed (through type inference and other techniques) for usability while preserving the type checking and protection offered by languages such as VB.Net, C# and Java. REXX (REstructured eXtended eXecutor) is an interpreted programming language which was developed at IBM. It is a structured high-level programming language which was designed to be both easy to learn and easy to read. ... Type inference is a feature present in some strongly statically typed programming languages. ... Visual Basic . ... The title given to this article is incorrect due to technical limitations. ... Java is an object-oriented programming language developed by James Gosling and colleagues at Sun Microsystems in the early 1990s. ...


Safely and unsafely typed

Main article: Type safety In computer science, a programming language is type safe when the language does not permit the programmer to treat a value as a type to which it does not belong. ...


A third way of categorising the type system of a programming language is by the safety of typed operations and convertions. The language is considered type safe if it does not allow operations or convertions which lead or erronous conditions.


Let us again have a look at the Visual Basic examples: Visual Basic (VB) is an event driven programming language and associated development environment, created by Microsoft. ...

 var x = 5; // (1) var y = "hi"; // (2) var z = x + y; // (3) 

The content of z in the example will be "5hi". While this might not be what the programmer intended the result is well defined and does not make the program crash or assign an undefined value to z. As it is, this Visual Basic example is type safe. Visual Basic (VB) is an event driven programming language and associated development environment, created by Microsoft. ...


Now let us look at the the same example in C:

 int x = 5; char y[] = "hi"; char* z = x + y; 

In this example z will point to a memory address three characters beyond z. What is stored at this location is undefined. Accessing z might even make the program crash. The program is erronous. C is an unsafely typed language.


Polymorphism and types

Main article: Polymorphism (computer science)

The term polymorphism refers to the ability of code (in particular, functions or classes) to act on values of multiple types, or to the ability of different instances of the same data-structure to contain elements of different types. Type systems that allow polymorphism generally do so in order to improve the potential for code re-use: in a language with polymorphism, programmers need only implement a data structure such as a list or a dictionary once, rather than once for each type of element with which they plan to use it. For this reason computer scientists sometimes call the use of certain forms of polymorphism generic programming. The type-theoretic foundations of polymorphism are closely related to those of abstraction, modularity and (in some cases) subtyping. In computer science, polymorphism means allowing a single definition to be used with different types of data (specifically, different classes of objects). ... In computer science, generics is a technique that allows one value to take different datatypes (so-called polymorphism) as long as certain contracts such as subtypes and signature are kept. ... In computer science, abstraction is a mechanism and practice to reduce and factor out details so that one can focus on few concepts at a time. ... In computing, a module is a software entity that groups a set of (typically cohesive) subprograms and data structures. ... ...


Explicit or implicit declaration and inference

Many static type systems, such as C's and Java's, require type declarations: the programmer must explicitly associate each variable with a particular type. Others, such as Haskell's, perform type inference: the compiler draws conclusions about the types of variables based on how programmers use those variables. For example, given a function f(x,y) which adds x and y together, the compiler can infer that x and y must be numbers -- since addition is only defined for numbers. Therefore, any call to f elsewhere in the program that specifies a non-numeric type (such as a string or list) as an argument would signal an error. Type inference is a feature present in some strongly statically typed programming languages. ...


Numerical and string constants and expressions in code can and often do imply type in a particular context. For example, an expression 3.14 might imply a type of floating-point; while [1, 2, 3] might imply a list of integers; typically an array. A floating-point number is a digital representation for a number in a certain subset of the rational numbers, and is often used to approximate an arbitrary real number on a computer. ... In computer programming, an array, also known as a vector or list (for one-dimensional arrays) or a matrix (for two-dimensional arrays), is one of the simplest data structures. ...


Collections of types

Types form natural collections that one can often index or list to find specific types of the kind described.

In computer science, primitive types, as distinct from composite types - are datatypes provided by a programming language as basic building blocks. ... The integers consist of the positive natural numbers (1, 2, 3, …), their negatives (−1, −2, −3, ...) and the number zero. ... A floating-point number is a digital representation for a number in a certain subset of the rational numbers, and is often used to approximate an arbitrary real number on a computer. ... In computer science, a variable has integral type if the variable represents an integer. ... A floating-point number is a digital representation for a number in a certain subset of the rational numbers, and is often used to approximate an arbitrary real number on a computer. ... A floating-point number is a digital representation for a number in a certain subset of the rational numbers, and is often used to approximate an arbitrary real number on a computer. ... In computer science, composite types are datatypes which can be constructed in a programming language out of that languages primitive types and other composite types. ... This article is about the data structure. ... This article needs to be cleaned up to conform to a higher standard of quality. ... ... A derived type is a type given a new type but structurally the same as the original type. ... In computer science, an object type (a. ... In computer science and mathematics, a variable is a symbol denoting a quantity or symbolic representation. ... In computing, a partial type is a data type definition which spans multiple source code files. ... In computer programming languages, a recursive type is a data type for values that may contain other values of the same type. ... A function object, often called a functor, is a computer programming construct allowing an object to be invoked or called as if it were an ordinary function, usually with the same syntax. ... In predicate logic, universal quantification is an attempt to formalise the notion that something (a logical predicate) is true for everything, or every relevant thing. ... In predicate logic, an existential quantification is the predication of a property or relation to at least one member of the domain. ...

Specialized types

Many different special kinds of types exist, each associated with particular kinds of instances.

In object-oriented programming, classes are used to group related variables and functions. ... WordNet gives four main senses for the English noun object: a physical entity; something that is within the grasp of the senses; an aim, target or objective — see Object (task); a grammatical Object — either a direct object or an indirect object the focus of cognitions or feelings. ... In computer science, object-oriented programming, OOP for short, is a computer programming paradigm. ... An interface defines the communication boundary between separate computer components. ... In computer science, dependency or coupling is the degree to which each program module relies on each other module. ... In computing, a protocol is a convention or standard that controls or enables the connection, communication, and data transfer between two computing endpoints. ... A Communications channel (or channel for short), models the medium through which information is transmitted from a sender (or transmitter) to a receiver. ... Kind can mean: Hundreds Bankekind Hundred - a hundred of Ostrogothia in Sweden Frökind Hundred - a hundred of Westrogothia in Sweden Hammarkind Hundred - a hundred of Ostrogothia in Sweden Hanekind Hundred - a hundred of Ostrogothia in Sweden Kind Hundred - a hundred divided between Hallandia, Smalandia and Westrogothia in Sweden Kinda... In software engineering, a use case is a technique for capturing the potential requirements of a new system or software change. ... Interaction is a kind of action which occurs as two or more objects have an effect upon one another. ... A layer is the following: In abstraction, a layer is an abstract place conceived as having depth. ... Used mainly in object-oriented programming, the term method refers to a piece of code that is exclusively associated either with a class (called class methods or static methods) or with an object (called instance methods). ...

Compatibility, equivalence and substitutability

The question of compatibility and equivalence becomes a complicated and controversial topic and relates to the problem of substitutability; in other words: given type A and type B, are they equal types or compatible? Can one use the value with type B in the place of the value with type A?


If type A is compatible with type B, A is a subtype of B (but not always vice versa) - according to the Liskov substitution principle. In object-oriented computer programming, the Liskov substitution principle is a particular definition of subtype that was introduced by Barbara Liskov and Jeannette Wing in a 1993 paper entitled Family Values: A Behavioral Notion of Subtyping. ...


Type conversion may take place in order to make a type compatible or substitutable in context. This article needs to be cleaned up to conform to a higher standard of quality. ...


Nominative vs structural typing

Main article: Nominative and structural type systems

Two primary schemes exist for distinguishing two types as equivalent and/or as subtypes; nominative (by name) and structural (by structure). As the names indicate, nominative type systems operate based on explicit annotations in the code; they "recognize" only explicitly declared types, and also require the explicit declaration of subtype relationships. Structural type systems, on the other hand, perform type judgements based on the structure of the two types under consideration. Nominative and structural type systems are two major classes of type system; differing in how a programming language determines whether or not two types are equivalent, and how it determines whether one type is a subtype of another. ...


Few languages implement nominative or structural schemes strictly; many have features of both. The major statically typed object oriented languages such as use nominative typing; the two major familes of functional programming languages use structural typing. On computer science, a datatype (often simply type) is a name or label for a set of values and some operations which can be performed on that set of values. ... Object-oriented programming (OOP) is a computer programming paradigm in which a software system is modeled as a set of objects that interact with each other. ... Functional programming is a programming paradigm that treats computation as the evaluation of mathematical functions. ...


Many popular languages show a fruitful combination: nominative type equivalence and structural subtyping; known as duck typing. It appears in many dynamically-typed OO languages. In computer science, duck typing is a term for the dynamic type system typical of some programming languages, such as with Smalltalk, where the variable value itself determines what it can do. ... On computer science, a datatype (often simply type) is a name or label for a set of values and some operations which can be performed on that set of values. ...


Type system cross reference list

edit talk
Programming language static / dynamic strong / weak safety Nominative / structural
Ada static strong safe nominative
assembly language none weak unsafe structural
BASIC static weak safe nominative
C static weak unsafe nominative
C++ static weak unsafe nominative
C# static strong safe nominative
Haskell static strong safe nominative
Java static strong safe nominative
Lisp dynamic strong safe structural
ML static strong safe structural
Objective-C 1 dynamic weak safe duck
Perl dynamic weak safe nominative
Python dynamic strong safe duck
Ruby dynamic weak safe duck
Scheme dynamic weak safe nominative
Smalltalk dynamic weak safe duck
  1. applies to the Objective-C extension only. The C basis is unchanged.

Computer code (HTML with JavaScript) in a tool that uses syntax highlighting (colors) to help the developer see the function of each piece of code. ... In computer science, a datatype or data type (often simply a type) is a name or label for a set of values and some operations which one can perform on that set of values. ... In computer science, a datatype or data type (often simply a type) is a name or label for a set of values and some operations which one can perform on that set of values. ... In computer science, a datatype or data type (often simply a type) is a name or label for a set of values and some operations which one can perform on that set of values. ... In computer science, a datatype or data type (often simply a type) is a name or label for a set of values and some operations which one can perform on that set of values. ... Ada is a structured, statically typed imperative computer programming language designed by a team led by Jean Ichbiah of CII Honeywell Bull during 1977–1983. ... Assembly language commonly called assembly or asm, is a human-readable notation for the machine language that a specific computer architecture uses. ... The word basic may refer to one of several articles in Wikipedia: Basic English BASIC programming language Basic (chemistry), the opposite to acidic, reacting with acids to form salts. ... The C Programming Language, Brian Kernighan and Dennis Ritchie, the original edition that served for many years as an informal specification of the language The C programming language is a standardized imperative computer programming language developed in the early 1970s by Dennis Ritchie for use on the Unix operating system. ... C++ (pronounced see plus plus, IPA: ) is a general-purpose computer programming language. ... C# redirects here. ... Haskell logo Haskell is a standardized pure functional programming language with non-strict semantics named after the logician Haskell Curry. ... Java is an object-oriented programming language developed by James Gosling and colleagues at Sun Microsystems in the early 1990s. ... Lisp is a family of computer programming languages with a long history and a distinctive fully-parenthesized syntax. ... ML is a general-purpose functional programming language developed by Robin Milner and others in the late 1970s at the University of Edinburgh, whose syntax is inspired by ISWIM. Historically, ML stands for metalanguage as it was conceived to develop proof tactics in the LCF theorem prover (the language of... Objective-C, often referred to as ObjC or more seldomly as Objective C or Obj-C, is an object oriented programming language implemented as an extension to C. It is used primarily on Mac OS X and GNUstep, two environments based on the OpenStep standard, and is the primary language... In computer science, duck typing is a term for the dynamic type system typical of some programming languages, such as with Smalltalk, where the variable value itself determines what it can do. ... Programming Republic of Perl logo Perl, also Practical Extraction and Report Language (a backronym, see below), is a programming language released by Larry Wall on December 18, 1987 that borrows features from C, sed, awk, shell scripting (sh), and (to a lesser extent) from many other programming languages. ... Python is an interpreted programming language created by Guido van Rossum in 1990. ... In computer science, duck typing is a term for the dynamic type system typical of some programming languages, such as with Smalltalk, where the variable value itself determines what it can do. ... Ruby is a reflective, object-oriented programming language. ... In computer science, duck typing is a term for the dynamic type system typical of some programming languages, such as with Smalltalk, where the variable value itself determines what it can do. ... Scheme is a functional programming language and a dialect of Lisp. ... Smalltalk is an object-oriented, dynamically typed, reflective, programming language designed at Xerox PARC by Alan Kay, Dan Ingalls, Ted Kaehler, Adele Goldberg, and others during the 1970s, influenced by Sketchpad and Simula. ... In computer science, duck typing is a term for the dynamic type system typical of some programming languages, such as with Smalltalk, where the variable value itself determines what it can do. ... Objective-C, often referred to as ObjC or more seldomly as Objective C or Obj-C, is an object oriented programming language implemented as an extension to C. It is used primarily on Mac OS X and GNUstep, two environments based on the OpenStep standard, and is the primary language... The C Programming Language, Brian Kernighan and Dennis Ritchie, the original edition that served for many years as an informal specification of the language The C programming language is a standardized imperative computer programming language developed in the early 1970s by Dennis Ritchie for use on the Unix operating system. ...

See also

Wikibooks
Wikibooks Ada Programming has more about this subject:
Types

  Results from FactBites:
 
DataType (437 words)
It is sometimes useful to discover if a DataType represents a real numeric value (i.e., can it be cast to a Double?) This returns True for both real scalar and array type.
It is occasionally useful to discover whether or not a DataType represents an array or scalar value.
These (overloaded) functions return DataType that corresponds to to the type that is being pointed at.
Datatype - Wikipedia, the free encyclopedia (2607 words)
In computer science, a datatype or data type (often simply a type) is a name or label for a set of values and some operations which one can perform on that set of values.
Programming languages implicitly or explicitly support one or more datatypes; these types may act as a statically or dynamically checked constraint, ensuring valid programs for a given language.
Assigning datatypes ("typing") has the basic purpose of giving some semantic meaning to otherwise meaningless collections of bits.
  More results at FactBites »

 
 

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