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In computer science, an associative array, map, symbol table, or dictionary is an abstract data type that stores a collection of (key, value) pairs, such that each possible key appears at most once in the collection. In mathematical terms, an associative array is a function with finite domain. [1] It supports 'lookup', 'remove', and 'insert ...
A small phone book as a hash table. In computer science, a hash table is a data structure that implements an associative array, also called a dictionary or simply map; an associative array is an abstract data type that maps keys to values. [3]
(with-hash-table-iterator (entry-generator phone-book) (loop do (multiple-value-bind (has-entry key value) (entry-generator) (if has-entry (format T "~&~s => ~s" key value) (loop-finish))))) It is easy to construct composite abstract data types in Lisp, using structures or object-oriented programming features, in conjunction with lists, arrays ...
In Python, == compares by value. Python's is operator may be used to compare object identities (comparison by reference), and comparisons may be chained—for example, a <= b <= c. Python uses and, or, and not as Boolean operators. Python has a type of expression named a list comprehension, and a more general expression named a generator ...
Tries are also disadvantageous when the key value cannot be easily represented as string, such as floating point numbers where multiple representations are possible (e.g. 1 is equivalent to 1.0, +1.0, 1.00, etc.), [12]: 359 however it can be unambiguously represented as a binary number in IEEE 754, in comparison to two's complement format. [17]
The "QMap" key/value dictionary (up to Qt 4) template class of Qt is implemented with skip lists. [13] Redis, an ANSI-C open-source persistent key/value store for Posix systems, uses skip lists in its implementation of ordered sets. [14] Discord uses skip lists to handle storing and updating the list of members in a server. [15]
Most database and spreadsheet programs are able to read or save data in a delimited format. Due to their wide support, DSV files can be used in data exchange among many applications. A delimited text file is a text file used to store data, in which each line represents a single book, company, or other thing, and each line has fields separated ...
Folds can be regarded as consistently replacing the structural components of a data structure with functions and values. Lists, for example, are built up in many functional languages from two primitives: any list is either an empty list, commonly called nil ([]), or is constructed by prefixing an element in front of another list, creating what is called a cons node ( Cons(X1,Cons(X2,Cons ...