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Undefined (other)
Undefined may refer to: Mathematics * Undefined (mathematics), with several related meanings ** Indeterminate form, in calculus Computing * Undefined behavior, computer code whose behavior is not specified under certain conditions * Undefined value, a condition where an expression does not have a correct value * Undefined variable * Undefined, a function or variable lacking a declaration * Undefined, a variable lacking initialization * Undefined, an unavailable linker symbol (function, or global variable) Other uses * Undefined, something that lacks definition * Undefined citizenship, a post-Soviet form of statelessness in Estonia See also * Null (other) * Void (other) * Invalid (other) * Definition (other) * Definable (other) In mathematical logic, the word definable may refer to: * A definable real number * A definable set In mathematical logic, a definable set is an ''n''-ary relation on the domain of a structure wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Undefined (mathematics)
In mathematics, the term undefined is often used to refer to an expression which is not assigned an interpretation or a value (such as an indeterminate form, which has the propensity of assuming different values). The term can take on several different meanings depending on the context. For example: * In various branches of mathematics, certain concepts are introduced as primitive notions (e.g., the terms "point", "line" and "angle" in geometry). As these terms are not defined in terms of other concepts, they may be referred to as "undefined terms". * A function is said to be "undefined" at points outside of its domainfor example, the real-valued function f(x)=\sqrt is undefined for negative x (i.e., it assigns no value to negative arguments). * In algebra, some arithmetic operations may not assign a meaning to certain values of its operands (e.g., division by zero). In which case, the expressions involving such operands are termed "undefined". Undefined terms In ancient tim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Indeterminate Form
In calculus and other branches of mathematical analysis, limits involving an algebraic combination of functions in an independent variable may often be evaluated by replacing these functions by their limits; if the expression obtained after this substitution does not provide sufficient information to determine the original limit, then the expression is called an indeterminate form. More specifically, an indeterminate form is a mathematical expression involving at most two of 0~, 1 or \infty, obtained by applying the algebraic limit theorem in the process of attempting to determine a limit, which fails to restrict that limit to one specific value or infinity, and thus does not determine the limit being sought. A limit confirmed to be infinity is not indeterminate since it has been determined to have a specific value (infinity). The term was originally introduced by Cauchy's student Moigno in the middle of the 19th century. There are seven indeterminate forms which are typically cons ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Undefined Behavior
In computer programming, undefined behavior (UB) is the result of executing a program whose behavior is prescribed to be unpredictable, in the language specification to which the computer code adheres. This is different from unspecified behavior, for which the language specification does not prescribe a result, and implementation-defined behavior that defers to the documentation of another component of the platform (such as the ABI or the translator documentation). In the C community, undefined behavior may be humorously referred to as "nasal demons", after a comp.std.c post that explained undefined behavior as allowing the compiler to do anything it chooses, even "to make demons fly out of your nose". Overview Some programming languages allow a program to operate differently or even have a different control flow than the source code, as long as it exhibits the same user-visible side effects, ''if undefined behavior never happens during program execution''. Undefined behavior ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Undefined Value
In computing (particularly, in programming), undefined value is a condition where an expression does not have a correct value, although it is syntactically correct. An undefined value must not be confused with empty string, Boolean "false" or other "empty" (but defined) values. Depending on circumstances, evaluation to an undefined value may lead to exception or undefined behaviour, but in some programming languages undefined values can occur during a normal, predictable course of program execution. Dynamically typed languages usually treat undefined values explicitly when possible. For instance, Perl has undef operator which can "assign" such value to a variable. In other type systems an undefined value can mean an unknown, unpredictable value, or merely a program failure on attempt of its evaluation. Nullable types offer an intermediate approach; see below. Handling The value of a partial function is undefined when its argument is out of its domain of definition. This in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Undefined Variable
An undefined variable in the source code of a computer program is a variable that is accessed in the code but has not been declared by that code."undefined variable." YourDictionary, n.d. Web. 24 July 2013. . In some programming languages, an implicit declaration is provided the first time such a variable is encountered at compile time. In other languages such a usage is considered to be sufficiently serious that a diagnostic being issued and the compilation fails. Some language definitions initially used the implicit declaration behavior and as they matured provided an option to disable it (e.g. Perl's "use warnings" or Visual Basic's "Option Explicit"). Examples The following provides some examples of how various programming language implementations respond to undefined variables. Each code snippet is followed by an error message (if any). CLISP (setf y x) *** - EVAL: variable X has no value C int main() foo.c: In function `main': foo.c:2: error: `x' undeclared (fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Declaration (computer Programming)
In computer programming, a declaration is a language construct specifying identifier properties: it declares a word's (identifier's) meaning."A declaration specifies the interpretation and attributes of a set of identifiers. A ''definition'' of an identifier is a declaration for that identifier that: * for an object ariable or constant causes storage to be reserved for that object; * for a function, includes the function body; * for an enumeration constant, is the (only) declaration of the identifier; * for a typedef name, is the first (or only) declaration of the identifier." C11 specification, 6.7: Declarations, paragraph 5. Declarations are most commonly used for functions, variables, constants, and classes, but can also be used for other entities such as enumerations and type definitions. Beyond the name (the identifier itself) and the kind of entity (function, variable, etc.), declarations typically specify the data type (for variables and constants), or the type signat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Initialization (programming)
In computer programming, initialization (or initialisation) is the assignment of an initial value for a data object or variable. The manner in which initialization is performed depends on the programming language, as well as the type, storage class, etc., of an object to be initialized. Programming constructs which perform initialization are typically called initializers and initializer lists. Initialization is distinct from (and preceded by) declaration, although the two can sometimes be conflated in practice. The complement of initialization is finalization, which is primarily used for objects, but not variables. Initialization is done either by statically embedding the value at compile time, or else by assignment at run time. A section of code that performs such initialization is generally known as "initialization code" and may include other, one-time-only, functions such as opening files; in object-oriented programming, initialization code may be part of a '' constructor'' (clas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dynamic Linker
In computing, a dynamic linker is the part of an operating system that loads and links the shared libraries needed by an executable when it is executed (at "run time"), by copying the content of libraries from persistent storage to RAM, filling jump tables and relocating pointers. The specific operating system and executable format determine how the dynamic linker functions and how it is implemented. Linking is often referred to as a process that is performed when the executable is compiled, while a dynamic linker is a special part of an operating system that loads external shared libraries into a running process and then binds those shared libraries dynamically to the running process. This approach is also called dynamic linking or late linking. Implementations Microsoft Windows Dynamic-link library, or DLL, is Microsoft's implementation of the shared library concept in the Microsoft Windows and OS/2 operating systems. These libraries usually have the file extension DL ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Definition
A definition is a statement of the meaning of a term (a word, phrase, or other set of symbols). Definitions can be classified into two large categories: intensional definitions (which try to give the sense of a term), and extensional definitions (which try to list the objects that a term describes).Lyons, John. "Semantics, vol. I." Cambridge: Cambridge (1977). p.158 and on. Another important category of definitions is the class of ostensive definitions, which convey the meaning of a term by pointing out examples. A term may have many different senses and multiple meanings, and thus require multiple definitions. In mathematics, a definition is used to give a precise meaning to a new term, by describing a condition which unambiguously qualifies what a mathematical term is and is not. Definitions and axioms form the basis on which all of modern mathematics is to be constructed. Basic terminology In modern usage, a definition is something, typically expressed in words, that attac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Undefined Citizenship
Estonian citizenship law details the conditions by which a person is a citizen of Estonia. The primary law currently governing these requirements is the Citizenship Act, which came into force on 1 April 1995. Estonia is a member state of the European Union (EU) and all Estonian citizens are EU citizens. They have automatic and permanent permission to live and work in any EU or European Free Trade Association (EFTA) country and may vote in elections to the European Parliament. Any person born to at least one Estonian parent receives Estonian citizenship at birth. Noncitizens may naturalise as Estonian citizens after living in the country for at least eight years as a permanent resident or on a valid long-term residence permit and showing proficiency in the Estonian language. Estonia was in 1940–1941 and 1944–1991 occupied by the Soviet Union and all local residents were considered citizens of the USSR by the former Soviet authorities. Since the restoration of the country ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Null (other)
Null may refer to: Science, technology, and mathematics Computing *Null (SQL) (or NULL), a special marker and keyword in SQL indicating that something has no value *Null character, the zero-valued ASCII character, also designated by , often used as a terminator, separator or filler. This symbol has no visual representation *Null pointer or reference (sometimes written NULL, nil, or None), an object pointer (or reference) not currently set to point (or refer) to a valid object Mathematics *Null (mathematics), a zero value in several branches of mathematics Physics *Null (physics), a point in a field where the field quantity is zero *Null (radio), a concept in electromagnetism Arts and media *The Null Corporation, an imprint of the band Nine Inch Nails * ''Null'' (Intronaut EP), 2006 * ''Null'' (Foetus EP), 1995 *Null, an identity of the character Gray Fox in the ''Metal Gear Solid: Portable Ops'' video game *Null, a villain from ''Teenage Mutant Ninja Turtles Adventures'' People ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Void (other)
Void may refer to: Science, engineering, and technology * Void (astronomy), the spaces between galaxy filaments that contain no galaxies * Void (composites), a pore that remains unoccupied in a composite material * Void, synonym for vacuum, a space containing no matter * Void, a bubble within a mechanical part that causes cavitation when it collapses * Void, an unwanted air pocket formed during injection moulding * VoID or Vocabulary of Interlinked Datasets, an RDF vocabulary to enable the discovery and use of linked data sets * Void coefficient, the change in the reactivity of a nuclear reactor when voids form in moderator or coolant fluids * Void Linux, a Linux distribution * Void ratio, the volume of void-space to solid space in a material * Void safety, in object-oriented programming, a guarantee that no object references will have null values * Void type, in programming languages, a keyword indicating the absence of data * Void set or empty set, the mathematical set with no ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
