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Oracle PL/SQL implements collections as programmer-defined types [1] Python: some built-in, others implemented in the collections library.NET provides the ICollection and IReadOnlyCollection interfaces and implementations such as List<T>. Rust provides the Vec<T> [2] and HashMap<K, V> [3] structs in the std::collections namespace. [4]
Python supports a wide variety of string operations. Strings in Python are immutable, so a string operation such as a substitution of characters, that in other programming languages might alter the string in place, returns a new string in Python. Performance considerations sometimes push for using special techniques in programs that modify ...
In computer science, a container is a class or a data structure [1] [2] whose instances are collections of other objects. In other words, they store objects in an organized way that follows specific access rules. The size of the container depends on the number of objects (elements) it contains.
The C language does not have collections or a foreach construct. However, it has several standard data structures that can be used as collections, and foreach can be made easily with a macro. However, two obvious problems occur: The macro is unhygienic: it declares a new variable in the existing scope which remains after the loop.
As a collection algorithm, reference counting tracks, for each object, a count of the number of references to it held by other objects. If an object's reference count reaches zero, the object has become inaccessible, and can be destroyed. When an object is destroyed, any objects referenced by that object also have their reference counts decreased.
Apple provides the NSCountedSet class as part of Cocoa, and the CFBag and CFMutableBag types as part of CoreFoundation. Python's standard library includes collections.Counter, which is similar to a multiset. Smalltalk includes the Bag class, which can be instantiated to use either identity or equality as predicate for inclusion test.
A collection may provide multiple iterators via its interface that provide items in different orders, such as forwards and backwards. An iterator is often implemented in terms of the structure underlying a collection implementation and is often tightly coupled to the collection to enable the operational semantics of the iterator.
In JavaScript (see also JSON), all objects behave as associative arrays with string-valued keys, while the Map and WeakMap types take arbitrary objects as keys. In Lua, they are used as the primitive building block for all data structures. In Visual FoxPro, they are called Collections. The D language also supports associative arrays. [22]