Associative array/Creation: Difference between revisions

=={{header|11l}}==

=={{header|8th}}==

8th has 'maps' as built-in data types, and can use JSON to describe them:

{ "one" : 1, "two" : "bad" }

Alternatively, they can be created in code:

m:new "one" 1 m:! "two" "bad" m:!

=={{header|AArch64 Assembly}}==

{{works with|as|Raspberry Pi 3B version Buster 64 bits <br> or android 64 bits with application Termux }}

/* ARM assembly AARCH64 Raspberry PI 3B or android 64 bits */

/* program hashmap64.s */

.include "../includeARM64.inc"

=={{header|ActionScript}}==

Because ActionScript does not have associative arrays in the normal sense, Object objects are used instead and keys are simply properties on those objects.

trace(map['key1']); // outputs "value1"

// More keys and values can then be added

map['key3'] = "value3";

''Note: The Object only supports String keys. To use an object as a key, try the flash.utils.Dictionary class.''

=={{header|Ada}}==

{{works with|GNAT|GPL 2007}}

with Ada.Strings.Unbounded; use Ada.Strings.Unbounded;

with Ada.Text_IO;

Value := Color_Map.Element(To_Unbounded_String("Yellow"));

Ada.Text_IO.Put_Line("Yellow:" & Integer'Image(Value));

=={{header|Aikido}}==

Aikido provides a native <em>map</em> for associative arrays. You can create them using a map literal and you can insert and remove items on the fly.

var names = {} // empty map

names["foo"] = "bar"

=={{header|Aime}}==

Aime records are heterogenous associative arrays. No creation procedure is required, declaration is fine.

r_put(r, "C", 2.5); # a real value

=={{header|ALGOL 68}}==

{{works with|ALGOL 68G|Any - tested with release [http://sourceforge.net/projects/algol68/files/algol68g/algol68g-1.18.0/algol68g-1.18.0-9h.tiny.el5.centos.fc11.i386.rpm/download 1.18.0-9h.tiny]}}

{{wont work with|ELLA ALGOL 68|Any (with appropriate job cards) - tested with release [http://sourceforge.net/projects/algol68/files/algol68toc/algol68toc-1.8.8d/algol68toc-1.8-8d.fc9.i386.rpm/download 1.8-8d] - due to extensive use of FORMATted transput}}

MODE COLOR = BITS;

printf(($g$,"values: ", comma sep, value OF color map items, $l$))

{{out}}

<pre>

Creating a new empty map of String to String:

Map<String, String> strMap = new Map<String, String>();

strMap.put('a', 'aval');

System.assertEquals( 'bval', strMap.get('b') );

// String keys are case-sensitive

Creating a new map of String to String with values initialized:

'a' => 'aval',

'b' => 'bval'

System.assert( strMap.containsKey('a') );

=={{header|APL}}==

{{works with|Dyalog APL}}

X←⎕NS ⍬

sales.revenue

4109.6

{{works with|GNU APL}}

⍝ Assign some names

X.this←'that'

sales.revenue

4109.6

=={{header|App Inventor}}==

=={{header|ARM Assembly}}==

{{works with|as|Raspberry Pi <br> or android 32 bits with application Termux}}

/* ARM assembly Raspberry PI or android 32 bits */

/* program hashmap.s */

.include "../affichage.inc"

=={{header|Arturo}}==

d: #[

name: "john"

]

{{out}}

=== Persistent association lists ===

The following implementation includes set, get, and delete, and also "generators", which are like iterators except they are closures rather than regular objects.

#define ATS_DYNLOADFLAG 0

end

{{out}}

Because the hash table is an AVL tree, performance will tend to be logarithmic. This assumes a good hash function, of course. With a bad hash function, performance may be linear.

#define ATS_DYNLOADFLAG 0

end

{{out}}

=== True arrays ===

[[AutoHotkey_L]] has [http://ahkscript.org/docs/Objects.htm Objects] which function as associative arrays.

MsgBox % associative_array.key1

=== Legacy versions ===

[[AutoHotkey_Basic]] does not have typical arrays.

However, variable names can be concatenated, simulating associative arrays.

arrayX2 = second

arrayX3 = foo

arrayX4 = bar

Loop, 4

=={{header|AutoIt}}==

See '''[https://msdn.microsoft.com/en-us/library/x4k5wbx4.aspx here]''' in the MSDN the reference for the Dictionary object that can be used in VBA. The following example shows how to create a dictionary, add/remove keys, change a key or a value, and check the existence of a key.

; All the required functions are below the examples.

;; End AA Functions.

=={{header|AWK}}==

Arrays in AWK are indeed associative arrays.

a["red"] = 0xff0000

a["green"] = 0x00ff00

print ( "red" in a ) # print 0

print ( "blue" in a ) # print 1

=={{header|Babel}}==

(("foo" 13)

("bar" 42)

=={{header|BaCon}}==

associative("abc") = "first three"

associative("xyz") = "last three"

{{out}}

=={{header|BASIC256}}==

dim values$[1]

dim keys$[1]

next n

return ""

{{out}}

<pre>a apple

This is cheating, I'm sure of it.

@echo off

setlocal ENABLEDELAYEDEXPANSION

echo %1 = %2

goto :eof

{{out}}

=={{header|BBC BASIC}}==

PROCputdict(mydict$, "FF0000", "red")

PROCputdict(mydict$, "00FF00", "green")

IF I% = 0 THEN = "" ELSE I% += LEN(key$) + 2

J% = INSTR(dict$, CHR$(0), I%)

=={{header|Bracmat}}==

The hash is the only built-in Bracmat class. It is best used for e.g. a large dictionary, when manipulation of a very long list of key/value pairs with pattern matching would become too CPU-intensive. The same key can be stored with different values, as the example shows. If that is not desirable, the key (and its value) should be removed first.

& (myhash..insert)$(title."Some title")

& (myhash..insert)$(formula.a+b+x^7)

& (myhash..remove)$formula

& (myhash..insert)$(formula.x^2+y^2)

{{out}}

<pre>(fruit.melons bananas) (fruit.apples oranges kiwis)

=={{header|Brat}}==

h[:a] = 1 #Assign value

h2 = [a: 1, b: [1 2 3], 10 : "ten"] #Initialized hash

=={{header|C}}==

=={{header|C sharp|C#}}==

'''Platform:''' [[.NET]] 1.x

'''Platform:''' [[.NET]] 2.0

{{works with|C sharp|C#|3.0+}}

=={{header|C++}}==

The C++ standard defines std::map as a means of creating an association between a key of one arbitrary type and a value of another arbitrary type. This requires the inclusion of the standard header '''map'''.

===Creation===

To create a simple map whose key is of type A and whose value is of type B, one would define the variable like so:

If one wanted to us a key type of '''int''' and a value of '''double''', you would define it like so:

===Insertion===

====Operator[]====

The first method is using the [] operator.

Of course, you can use a variable (or any [[rvalue]] of the correct type) for the key or value parameters:

double myValue = 3.14;

====insert()====

The second approach is a little more complicated. We have to use the '''pair<>''' template:

or by using '''make_pair''' to avoid repeating key/value types:

===Lookup===

====operator[]====

We use it as an rvalue, supplying the correct key:

If the value doesn't already exist, a default-constructed object of the value's type will be inserted using the key you specified, and that default value will be returned.

====find()====

Alternatively, you can look up a value by using find(), storing its return value in an [[iterator]], and comparing the iterator against the map's end() [[sentinal value]]:

std::map<int, double>::iterator myIterator = exampleMap.find(myKey);

if(exampleMap.end() != myIterator)

// Return the value for that key.

myValue = myIterator->second;

The need for the '''->second''' code is because our iterator points to a '''pair<>()''', and our value is the second member of that pair.

===Example===

This simple program creates a map, assigns a value to that map, retrieves a value from that map, and prints the value to STDOUT.

#include <iostreams>

// main() must return 0 on success.

return 0;

=={{header|Ceylon}}==

ArrayList,

}

=={{header|Chapel}}==

writeln("arr2 keys: ", arr2.domain);

{{out}}

=={{header|Clojure}}==

:key2 "value2"

=={{header|ColdFusion}}==

<cfset myHash.key1 = "foo">

<cfset myHash["key2"] = "bar">

In ColdFusion, a map is literally a java.util.HashMap, thus the above 3rd method is possible.

=={{header|Common Lisp}}==

;; or for implementation identity for other types!

;; Use #'equalp if you want case-insensitive keying on strings.

;; alist is written like this:

(defparameter *legs* '((cow . 4) (flamingo . 2) (centipede . 100)))

=={{header|Component Pascal}}==

BlackBox Componente Builder<br/>

Using a handmade collections module with the following interface<br/>

DEFINITION Collections;

END Collections.

The program:

MODULE BbtAssociativeArrays;

IMPORT StdLog, Collections, Boxes;

END BbtAssociativeArrays.

Execute:^Q BbtAssociativeArrays.Do<br/>

{{out}}

=={{header|Crystal}}==

# hash literals that don't perfectly match the intended hash type must be given an explicit type specification

# the following would fail without `of String => String|Int32`

=={{header|D}}==

auto hash = ["foo":42, "bar":100];

assert("foo" in hash);

=={{header|Dao}}==

h = { -> } # empty hash map, future inserted keys will not be ordered

m = { 'foo' => 42, 'bar' => 100 } # with ordered keys

=={{header|Dart}}==

main() {

var rosettaCode = { // Type is inferred to be Map<String, String>

}

{{out}}

<pre>

=={{header|Delphi}}==

{$APPTYPE CONSOLE}

lDictionary.Free;

end;

=={{header|Diego}}==

To create a dictionary associative array:

add_dict(tanzanianBanknoteObverseDipiction)_keys(500,1000,2000,5000,10000)_values(Karume,Nyerere,lion,black rhinoceros,elephant);

To create a hash associative array:

add_hash(tanzanianBanknoteReverseDipiction)_values(

);

=={{header|Dyalect}}==

Dyalect has a <code>Tuple</code> data type which allows to add labels to values:

{{out}}

=={{header|E}}==

["one" => 1, "two" => 2] # immutable, 2 mappings

[].asMap().diverge() # mutable, empty

["one" => 2].diverge(String, float64) # mutable, initial contents,

=={{header|EchoLisp}}==

(lib 'hash) ;; needs hash.lib

(define H (make-hash)) ;; new hash table

(hash-count H)

→ 3

=={{header|Elena}}==

ELENA 5.0:

public program()

map["key3"]:= "foo3";

map["key4"]:= "foo4";

=== Strong typed dictionary ===

public program()

map["key3"]:= "foo3";

map["key4"]:= "foo4";

=={{header|Elixir}}==

{{trans|Erlang}}

def test_create do

IO.puts "< create Map.new >"

end

{{out}}

=={{header|Emacs Lisp}}==

<code>make-hash-table</code> compares keys with <code>eql</code> by default. This suits symbols and numbers (including floating point). For string keys an <code>equal</code> test can be used,

<code>define-hash-table-test</code> can create other key comparison types.

=={{header|Erlang}}==

Erlang offers several associative array type data structures, this example uses the dictionary data structure.

-module(assoc).

-compile([export_all]).

io:format("~p: ~b~n",[K,dict:fetch(K,D)])

end, dict:fetch_keys(D)).

{{out}}

=={{header|F Sharp|F#}}==

.NET 3.5 Generic Dictionary (mutable)

let dic = System.Collections.Generic.Dictionary<string,string>() ;;

dic.Add("key","val") ;

dic.["key"] <- "new val" ;

Functional dictionary (immutable)

let d = [("key","val");("other key","other val")] |> Map.ofList

let newd = d.Add("new key","new val")

| Some(v) -> printfn "%s" v

| None -> printfn "not found"

=={{header|Factor}}==

Associative mappings follow the associative protocol. See [http://docs.factorcode.org/content/article-assocs-protocol.html the docs].

Here's an example using a hashtable that can be run in the listener :

{ [ "one" swap at . ]

[ 2 swap value-at . ]

[ "three" swap at . ]

[ [ 3 "three" ] dip set-at ]

=={{header|Fantom}}==

Associative arrays are called 'maps' in Fantom:

class Main

{

}

}

=={{header|Forth}}==

The Forth dictionary is normally only used for function and symbol definitions, but you can also define separate ''wordlists'' for holding functions or data. There is no special syntax in the language for this, but you can define your own. All of Forth's defining words are available for adding things to the wordlist, but CREATE is most generic.

search-wordlist if

>body @

s" alpha" bar get . \ 5

8 s" Alpha" bar put \ Forth dictionaries are normally case-insensitive

This is not necessarily a good option in all Forths, as the dictionary may be implemented as a simple linked list (normally not a problem because the dictionary is only used for compiling and interactive interpretation). [[GNU Forth]] and many other hosted Forths use hash tables for the dictionary, so this is a fine choice. If you need case-sensitive keys, GNU Forth has <tt>table</tt> and <tt>table-find</tt>, replacing <tt>wordlist</tt> and <tt>search-wordlist</tt>, respectively.

Hashtable for mapping strings to integer

\ Create a hash table 'table' in the dictionary with a starting size of 10

[ELSE]

.( Entry not present.) cr

{{works with|4tH|3.64}}

.( Value: ) . cr

then

=={{header|FreeBASIC}}==

Uses unions to store the keys and associated values, and FreeBASIC's ability to resize arrays makes adding new entries easy.

enum datatype

print Dictionary(0).value.value.strng

{{out}}

<pre>

=={{header|Free Pascal}}==

FPC 3.2.0.+. Similar to Delphi.

{$IFDEF FPC}{$MODE DELPHI}{$ENDIF}

{$IFDEF WINDOWS}{$APPTYPE CONSOLE}{$ENDIF}

lDictionary.Free;

end;

FPC 2.4+. Using FGL instead of rtl-generics:

{$IFDEF WINDOWS}{$APPTYPE CONSOLE}{$ENDIF}

{$MODE DELPHI}

lDictionary.Free;

end;

=={{header|Futhark}}==

=={{header|Gambas}}==

=={{header|Go}}==

Allowable key types are those with == and != operators. This includes is boolean, numeric, string, pointer, channel, and interface types. It also includes structs and arrays containing only these types. Disallowed as map keys are all slice, function, and map types.

var x map[string]int

x = map[string]int{

"foo": 2, "bar": 42, "baz": -1,

=={{header|Gosu}}==

As an OOP language with generics Gosu can use any variety of Map classes. In addition Gosu provides associative array syntax for all objects.

var emptyMap = new HashMap<String, Integer>()

var scott = new Person()

scott["name"] = "Scott"

=={{header|Groovy}}==

Create an empty map and add values

map[7] = 7

map['foo'] = 'foovalue'

assert 'foovalue' == map.foo

assert 'barvalue' == map['bar']

Create a pre-populated map and verify values

assert 7 == map[7]

assert 'foovalue' == map.foo

assert 'barvalue' == map['bar']

=={{header|Harbour}}==

Create an empty array and add values:

arr[ 10 ] := "Val_10"

Create and initialize array:

// or

=={{header|Haskell}}==

Binary trees:

{{works with|GHC}}

dict = fromList [("key1","val1"), ("key2","val2")]

ans = Data.Map.lookup "key2" dict -- evaluates to Just "val2"

It is also possible to use association lists (lists of pairs). It is inefficient (O(n) lookup), but simple.

ans = lookup "key2" dict -- evaluates to Just "val2"

GHC also had an imperative hash table implementation in the <code>Data.HashTable</code> module, but was removed in <code>GHC 7.8</code>.

=={{header|hexiscript}}==

let d["test"] "test" # Strings can be used as index

let d[123] 123 # Integers can also be used as index

println d["test"]

=={{header|Icon}} and {{header|Unicon}}==

Icon and Unicon associative arrays are called tables. Any value may be used as a key including complex structures. Tables can have default values and they have no inherent size limitation growing from empty to whatever size is needed.

local t

t := table()

t["foo"] := "bar"

write(t["foo"])

=={{header|Inform 7}}==

===Static relation===

Connection relates various texts to one number. The verb to be connected to implies the connection relation.

let V be the number that "baz" relates to by the connection relation;

say "'baz' => [V].";

===Dynamic relation===

When play begins:

let V be the number that "baz" relates to by R;

say "'baz' => [V].";

=={{header|Ioke}}==

=={{header|J}}==

However, it's also possible to use the symbol table itself to hold the names. The symbol table has limitations (can only accept syntactically valid names), but we can turn arbitrary strings into valid symbols using base 62 encode and prefixing with a letter (hypothetically speaking, base 64 encode would let us build longer names than base 62, because of computational complexity issues - but the J symbol table also comes with a name length limit - 255 characters - and does not support 64 different characters in names):

encode=: 'z', (a.{~;48 65 97(+ i.)&.>10 26 26) {~ 62x #.inv 256x #. a.&i.

get=: ".@encode

has=: 0 <: nc@<@encode

Example use:

'foo' set__example 1 2 3

1 2 3

get__example 'bletch'

7 8 9

Note that J's symbols (http://www.jsoftware.com/help/dictionary/dsco.htm) might also be used for this purpose. However, symbols are not garbage collected within a J session (and, instead, a mechanism is provided to optionally preserve them across sessions).

Defining the Map:

map.put("foo", 5);

map.put("bar", 10);

map.put("baz", 15);

"Putting" a value for a key that already exists ("map.put("foo", 6)" in this example) will replace and return the old value for the key.

Initializing a Map as a class member:

put("foo", 5);

put("bar", 10);

put("baz", 15);

put("foo", 6);

Retrieving a value:

Note that it is possible to put <code>null</code> as a value, so <code>null</code> being returned by <code>get</code> is not sufficient for determining that the key is not in the <code>Map</code>. There is a <code>containsKey</code> method for that.

Iterate over keys:

Iterate over values:

Iterate over key, value pairs:

=={{header|JavaScript}}==

Javascript object property names (keys) are strings. Other types and expressions can be used with square bracket notation, they are evaluated and converted to strings and the result used as the property name. Using quotes on property names avoids potential collisions with reserved JavaScript key words.

assoc['foo'] = 'bar';

alert('key:"' + key + '", value:"' + assoc[key] + '"');

}

ECMAScript 6 (ES6) offers both a map and a weak map implementation. While Objects must use strings, Maps may use objects, functions, and numbers as keys in addition to strings.

fn = function () {},

obj = {};

for (var key of map.keys()) {

console.log(key + ' => ' + map.get(key));

=={{header|jq}}==

===Associative Arrays with String-Valued Keys===

In jq, JSON objects can be used as associative arrays, it being understood that only strings can be used as keys. To avoid confusion, for the remainder of this section, we refer to JSON objects as such. Their type in jq is "object".

{}

# Alteration of the value of an existing key:

===Associative Arrays with JSON-Valued Keys===

In this subsection, we define addKey(key;value), getKey(key), and removeKey(key)

to operate on a hash table for which the keys may be any JSON entities. This is done by defining a collisionless hash function.

if type == "object" then with_entries(.value = (.value|collisionless))|tostring

elif type == "array" then map(collisionless)|tostring

def getKey(key): .[key|collisionless];

'''Example''':

produces:

=={{header|Jsish}}==

From Javascript. jsish warns of duplicate ''var'', in this case the ''assoc'' variable is reused.

assoc['foo'] = 'bar';

assoc ==> { "another-key":3, foo:"bar" }

=!EXPECTEND!=

{{out}}

<pre>prompt$ jsish -u associativeArray.jsi

{{works with|Julia|0.6}}

We build dictionaries associating to some characters their code points, by listing the key/value pairs, through a dictionary comprehension, by creating an empty dictionary and filling it, by using the specific syntax associated to typed dictionaries.

# Dict{Char,Int64} with 2 entries:

# 'b' => 98

typeof(dict) # type is infered correctly

# Dict{Char,Int64}

=={{header|K}}==

Keys in a dictionary must be symbols (`symbol).

d1:.((`foo;1); (`bar;2); (`baz;3))

/ extracting a value

d1[`bar]

Another approach.

d2[`"zero"]:0

d2[`"one"]:1

.((`zero;0;)

(`one;1;)

Extracting the keys and values.

`zero `one `two

d2[] / the values

=={{header|Kotlin}}==

{{trans|Java}}

// map definition:

val map = mapOf("foo" to 5,

// iterate over key, value pairs:

for ((k, v) in map) println("$k => $v")

=={{header|Lambdatalk}}==

Associative arrays are not currently built in the JS.js kernel of lambdatalk but are added via the lib_hash library page.

1) a (currently) reduced set of functions:

bar: Barcelona, Catalunya

]

=={{header|Lang5}}==

: first 0 extract nip ; : second 1 extract nip ;

'bar over at .

'hello 'bar rot set-at

=={{header|langur}}==

Hash keys in langur may be numbers or strings. Number keys are simplified, so that 1.0 is the same key as 1.

# may assign with existing or non-existing hash key (if hash is mutable)

# using an alternate value in case of invalid index; prevents exception

writeln .hash[1; 42]

{{out}}

=={{header|Lasso}}==

// Define an empty map

#1 -> reverse

}

=={{header|LFE}}==

(let* ((my-dict (: dict new))

(my-dict (: dict store 'key-1 '"value 1" my-dict))

(: io format '"some data: ~p~n" (list (: dict fetch 'key-1 my-dict))))

=={{header|Liberty BASIC}}==

Needs the sublist library from http://basic.wikispaces.com/SubList+Library since LB does not have built-in associative arrays.

data "red", "255 50 50", "green", "50 255 50", "blue", "50 50 255"

data "my fave", "220 120 120", "black", "0 0 0"

print " Key 'green' is associated with data item "; sl.Get$( myAssocList$, "green")

Key 'green' is associated with data item 50 255 50

=={{header|Lingo}}==

put props[#key2]

-- "value2"

put props.getProp(#key2)

=={{header|LiveCode}}==

Livecode arrays are only associative, but can be accessed by ordinal if they are used as the key.

local tArray

put "value 1" into tArray["key 1"]

"length of item 3:" && the length of tArray["abc"] & return & \

"keys:" && the keys of tArray

Output

length of item 3: 5

keys: key numbers

abc

=={{header|Logo}}==

[[UCB Logo]] has "property lists" which associate names with values. They have their own namespace.

pprop "animals "dog 4

pprop "animals "mouse 11

print gprop "animals "cat ; 5

remprop "animals "dog

=={{header|LOLCODE}}==

BUKKITs are associative arrays

I HAS A Hash ITZ A BUKKIT

Hash HAS A key1 ITZ "val1" BTW This works for identifier-like keys, like obj.key in JavaScript

VISIBLE Hash'Z SRS "key-2"

KTHXBYE

{{Out}}

<pre>1</pre>

=={{header|Lua}}==

Lua tables are Hashes

hash[ "key-1" ] = "val1"

hash[ "key-2" ] = 1

Returns nil on unknown key.

=={{header|M2000 Interpreter}}==

Μ2000 has Inventory object to use it as a Map. All keys converted to strings. If a key has no value then key is the value until we place one. A special type of Inventory is the Inventory Queue, where we can use same keys, and we can't delete except from the last append.

Inventory A="100":=1, "200":=5, 10:=500, 20:="Hello There"

Print len(A)

If Exist(A, "End") Then Print Eval(A)=5000

=={{header|Maple}}==

Maple tables are hashed arrays. A table can be constructed by using the table constructor.

T := table(["foo" = 1, sin(x) = cos(x), (2, 3) = 4])

> T["foo"];

New entries are added by assignment.

T["bar"] := 2

> T[ "bar" ];

Entries can be removed as follows.

T["foo"] := T["foo"]

> T[ "foo" ];

(The latter output indicates that T["foo"] is an unassigned name.)

=={{header|Mathematica}} / {{header|Wolfram Language}}==

=={{header|MATLAB}} / {{header|Octave}}==

Associative arrays are called structs. The following methods of creating hash are equivalent.

hash.b = 2;

alternatively

hash = setfield(hash,'a',1);

hash = setfield(hash,'b',2);

or

hash.('b') = 2;

<pre>>> disp(hash)

===MATLAB only: containers.Map===

Use of containers.Map removes some restrictions on key types that structs have. Keys can all be numeric or all be strings. Values can be of any type. Key and value types cannot be changed after creation of the containers.Map object.

is equivalent to

m('a') = 1;

m('b') = 2;

since the KeyType defaults to 'char'. For numeric keys, the key and value types must be specified at creation.

is equivalent to