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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 ...
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:
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.
Perl has been referred to as "line noise" and a "write-only language" by its critics. Randal L. Schwartz in the first edition of the book Learning Perl, [96] in the first chapter states: Yes, sometimes Perl looks like line noise to the uninitiated, but to the seasoned Perl programmer, it looks like checksummed line noise with a mission in life ...
1960, IFIP WG 2.1, ISO [8] ALGOL 68: Application Yes No Yes Yes Yes No Concurrent Yes 1968, IFIP WG 2.1, GOST 27974-88, [9] Ateji PX: Parallel application No Yes No No No No pi calculus: No APL: Application, data processing: Yes Yes Yes Yes Yes Yes Array-oriented, tacit: Yes 1989, ISO Assembly language: General Yes No No No No No
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.
^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
Line continuation – escapes a newline to continue a statement on the next line Some languages define a special character as a terminator while some, called line-oriented , rely on the newline . Typically, a line-oriented language includes a line continuation feature whereas other languages have no need for line continuation since newline is ...