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Similarly, the empty space is the unique initial object in Top, the category of topological spaces and every one-point space is a terminal object in this category. In the category Rel of sets and relations, the empty set is the unique initial object, the unique terminal object, and hence the unique zero object. Morphisms of pointed sets.
The object pool design pattern creates a set of objects that may be reused. When a new object is needed, it is requested from the pool. If a previously prepared object is available, it is returned immediately, avoiding the instantiation cost. If no objects are present in the pool, a new item is created and returned.
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".
This permits a high degree of object code optimization by the compiler, but requires C programmers to take more care to obtain reliable results than is needed for other programming languages. Kernighan and Ritchie say in the Introduction of The C Programming Language: "C, like any other language, has its blemishes. Some of the operators have ...
A free object on X is a pair consisting of an object in C and an injection : (called the canonical injection), that satisfies the following universal property: For any object B in C and any map between sets g : X → U ( B ) {\displaystyle g:X\to U(B)} , there exists a unique morphism f : A → B {\displaystyle f:A\to B} in C such that g = U ...
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 (class method) or an initializer (instance method).
In object-oriented design, a pattern is a named description of a problem and solution that can be applied in new contexts; ideally, a pattern advises us on how to apply its solution in varying circumstances and considers the forces and trade-offs.
Creating objects directly within the class that requires (uses) the objects is inflexible because it commits the class to particular objects at compile-time and makes it impossible to specify which objects to create at run-time. The prototype design pattern describes how to solve such problems: Define a Prototype object that returns a copy of ...