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Read-only data types (sources) can be covariant; write-only data types (sinks) can be contravariant. Mutable data types which act as both sources and sinks should be invariant. To illustrate this general phenomenon, consider the array type. For the type Animal we can make the type Animal [], which is an "array of animals". For the purposes of ...
First-class functions have often only been supported in later revisions of the language, including C# 2.0 and Apple's Blocks extension to C, C++, and Objective-C. C++11 has added support for anonymous functions and closures to the language, but because of the non-garbage collected nature of the language, special care has to be taken for non ...
The term closure is often used as a synonym for anonymous function, though strictly, an anonymous function is a function literal without a name, while a closure is an instance of a function, a value, whose non-local variables have been bound either to values or to storage locations (depending on the language; see the lexical environment section below).
Purely functional data structures are often represented in a different way than their imperative counterparts. [6] For example, array with constant-time access and update is a basic component of most imperative languages and many imperative data-structures, such as hash table and binary heap, are based on arrays.
A block definition produces an opaque value which contains both a reference to the code within the block and a snapshot of the current state of local stack variables at the time of its definition. The block may be later invoked in the same manner as a function pointer.
In computing, a persistent data structure or not ephemeral data structure is a data structure that always preserves the previous version of itself when it is modified. Such data structures are effectively immutable , as their operations do not (visibly) update the structure in-place, but instead always yield a new updated structure.
Conversely, the mutable keyword allows a class member to be changed even if an object was instantiated as const. Even functions can be const in C++. The meaning here is that only a const function may be called for an object instantiated as const; a const function doesn't change any non-mutable data.
A data structure known as a hash table.. In computer science, a data structure is a data organization and storage format that is usually chosen for efficient access to data. [1] [2] [3] More precisely, a data structure is a collection of data values, the relationships among them, and the functions or operations that can be applied to the data, [4] i.e., it is an algebraic structure about data.