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Perl 5 has built-in, language-level support for associative arrays. Modern Perl refers to associative arrays as hashes; the term associative array is found in older documentation but is considered somewhat archaic. Perl 5 hashes are flat: keys are strings and values are scalars.
In an associative array, the association between a key and a value is often known as a "mapping"; the same word may also be used to refer to the process of creating a new association. The operations that are usually defined for an associative array are: [3] [4] [8] Insert or put
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]
The disadvantage of association lists is that the time to search is O, where n is the length of the list. [3] For large lists, this may be much slower than the times that can be obtained by representing an associative array as a binary search tree or as a hash table. Additionally, unless the list is regularly pruned to remove elements with ...
^d Although Perl doesn't have records, because Perl's type system allows different data types to be in an array, "hashes" (associative arrays) that don't have a variable index would effectively be the same as records. ^e Enumerations in this language are algebraic types with only nullary constructors
Perl programmers may initialize a hash (or associative array) from a list of key/value pairs. If the keys are separated from the values with the => operator (sometimes called a fat comma), rather than a comma, they may be unquoted (barewords [5]). The following lines are equivalent:
Regular expression (Perl compatible regular expressions ("PCRE") version 8.41 with UTF-8 support) [6] An important differentiator to JSON is that BSON contains types not present in JSON (e.g. datetime, byte array, and proper IEEE 754 floats) and offers type-strict handling for several numeric types instead of a universal "number" type.
In addition to support for vectorized arithmetic and relational operations, these languages also vectorize common mathematical functions such as sine. For example, if x is an array, then y = sin (x) will result in an array y whose elements are sine of the corresponding elements of the array x. Vectorized index operations are also supported.