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In object-oriented computer programming, a null object is an object with no referenced value or with defined neutral (null) behavior.The null object design pattern, which describes the uses of such objects and their behavior (or lack thereof), was first published as "Void Value" [1] and later in the Pattern Languages of Program Design book series as "Null Object".
Perl autovivification can be contrasted against languages such as Python, PHP, Ruby, and many of the C style languages, where dereferencing null or undefined values is not generally permitted. [ a ] It can be compared to the HTML standard's "named access on the window object" [ 2 ] which results in corresponding globally scoped variables being ...
This class of status code indicates the client must take additional action to complete the request. Many of these status codes are used in URL redirection. [2]A user agent may carry out the additional action with no user interaction only if the method used in the second request is GET or HEAD.
Nullable types are a feature of some programming languages which allow a value to be set to the special value NULL instead of the usual possible values of the data type.In statically typed languages, a nullable type is an option type, [citation needed] while in dynamically typed languages (where values have types, but variables do not), equivalent behavior is provided by having a single null ...
In C, variables with static storage duration that are not initialized explicitly are initialized to zero (or null, for pointers). [ 3 ] Not only are uninitialized variables a frequent cause of bugs, but this kind of bug is particularly serious because it may not be reproducible: for instance, a variable may remain uninitialized only in some ...
For example, the pyramid of doom is commonly seen when checking for null pointers or handling callbacks. [1] Two examples of the term are related to a particular programming style in early versions of JavaScript, [2] and the nesting of if statements that occurs in object-oriented programming languages when one of the objects may be a null ...
In object-oriented programming, the safe navigation operator (also known as optional chaining operator, safe call operator, null-conditional operator, null-propagation operator) is a binary operator that returns null if its first argument is null; otherwise it performs a dereferencing operation as specified by the second argument (typically an ...
In some programming language environments (at least one proprietary Lisp implementation, for example), [citation needed] the value used as the null pointer (called nil in Lisp) may actually be a pointer to a block of internal data useful to the implementation (but not explicitly reachable from user programs), thus allowing the same register to be used as a useful constant and a quick way of ...