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defines an immutable entity maxValue (the integer type is inferred at compile-time) and a mutable entity named currentValue. By default, collection classes such as List and Map are immutable, so update-methods return a new instance rather than mutating an existing one. While this may sound inefficient, the implementation of these classes and ...
Python makes a distinction between lists and tuples. Lists are written as [1, 2, 3], are mutable, and cannot be used as the keys of dictionaries (dictionary keys must be immutable in Python). Tuples, written as (1, 2, 3), are immutable and thus can be used as keys of dictionaries, provided all of the tuple's elements are immutable.
Python sets are very much like mathematical sets, and support operations like set intersection and union. Python also features a frozenset class for immutable sets, see Collection types. Dictionaries (class dict) are mutable mappings tying keys and corresponding values. Python has special syntax to create dictionaries ({key: value})
Perhaps the simplest persistent data structure is the singly linked list or cons-based list, a simple list of objects formed by each carrying a reference to the next in the list. This is persistent because the tail of the list can be taken, meaning the last k items for some k, and new nodes can be added in front of it. The tail will not be ...
Many widely used languages, such as C++, Java, and Python, provide object-oriented features. Although in the past object-oriented programming was widely accepted, [ 51 ] more recently essays criticizing object-oriented programming and recommending the avoidance of these features (generally in favor of functional programming ) have been very ...
Because fields in C# classes are always mutable, variantly parameterized classes in C# would not be very useful. But languages which emphasize immutable data can make good use of covariant data types. For example, in all of Scala, Kotlin and OCaml the immutable list type is covariant: List [Cat] is a subtype of List [Animal].
In C#, a class is a reference type while a struct (concept derived from the struct in C language) is a value type. [5] Hence an instance derived from a class definition is an object while an instance derived from a struct definition is said to be a value object (to be precise a struct can be made immutable to represent a value object declaring attributes as readonly [6]).