Comparison of programming languages (associative array): Difference between revisions

Revision as of 21:34, 25 August 2020

Revision as of 14:01, 29 September 2020

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An associative array can be declared using the following syntax:

<syntaxhighlight lang=PHP"php">

$phonebook = array();

$phonebook['Sally Smart'] = '555-9999';

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PHP can loop through an associative array as follows:

<syntaxhighlight lang=PHP"php">

foreach ($phonebook as $name => $number) {

echo 'Number for ', $name, ': ', $number, "\n";

}

// For the last array example it is used like this

foreach ($phonebook['contacts'] as $name => $num) {

echo 'Name: ', $name, ', number: ', $num['number'], "\n";

}

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[[Pike (programming language)|Pike]] has built-in support for associative arrays, which are referred to as mappings. Mappings are created as follows:

<syntaxhighlight lang=Pike"pike">

mapping(string:string) phonebook = ([

"Sally Smart":"555-9999",

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Iterating through a mapping can be done using <code>foreach</code>:

<syntaxhighlight lang="pike">

foreach(phonebook; string key; string value) {

write("%s:%s\n", key, value);

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Or using an iterator object:

<syntaxhighlight lang="pike">

Mapping.Iterator i = get_iterator(phonebook);

while (i->index()) {

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Elements of a mapping can be removed using <code>m_delete</code>, which returns the value of the removed index:

<syntaxhighlight lang="pike">

string sallys_number = m_delete(phonebook, "Sally Smart");

</syntaxhighlight>

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<syntaxhighlight lang="python">

>>> del phonebook['"John Doe'"]

>>> val = phonebook.pop('"Sally Smart'")

>>> phonebook.keys() # Only one key left

['J. Random Hacker']

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A map can be written as a literal, such as <code>#(key1 value1 key2 value2 ...)</code>, or can be created using <code>make map! [key1 value1 key2 value2 ...]</code>:

<syntaxhighlight lang=Red"red">

Red [Title:"My map"]

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In [[REXX]], associative arrays are called "stem variables" or "Compound variables".

<syntaxhighlight lang=REXX"rexx">

KEY = 'Sally Smart'

PHONEBOOK.KEY = '555-9999'

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by convention contains the total number of items in the stem:

<syntaxhighlight lang=REXX"rexx">

NAME.1 = 'Sally Smart'

NAME.2 = 'John Doe'

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In [[Ruby programming language|Ruby]] a hash table is used as follows:

<syntaxhighlight lang="irb">

irb(main):001:0> phonebook = {

irb(main):002:1* 'Sally Smart' => '555-9999',

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Ruby supports hash looping and iteration with the following syntax:

<syntaxhighlight lang="irb">

irb(main):007:0> ### iterate over keys and values

irb(main):008:0* phonebook.each {|key, value| puts key + " => " + value}

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[[Scala (programming language)|Scala]] provides an immutable <code>Map</code> class as part of the <code>scala.collection</code> framework:

<syntaxhighlight lang=Scala"scala">

val phonebook = Map("Sally Smart" -> "555-9999",

"John Doe" -> "555-1212",

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Scala's [[type inference]] will decide that this is a <code>Map[String, String]</code>. To access the array:

<syntaxhighlight lang=Scala"scala">

phonebook.get("Sally Smart")

</syntaxhighlight>

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In [[Smalltalk]] a <code>Dictionary</code> is used:

<syntaxhighlight lang=Smalltalk"malltalk">

phonebook := Dictionary new.

phonebook at: 'Sally Smart' put: '555-9999'.

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To access an entry the message <code>#at:</code> is sent to the dictionary object:

<syntaxhighlight lang=Smalltalk"smalltalk">

phonebook at: 'Sally Smart'

</syntaxhighlight>

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Which gives:

<syntaxhighlight lang=Text"text">

'555-9999'

</syntaxhighlight>