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There is no standard implementation of associative arrays in [[C (programming language)|C]], but a 3rd-party library, C Hash Table, with BSD license, is available.<ref>[https://web.archive.org/web/20071015024120/http://www.cl.cam.ac.uk/~cwc22/hashtable/ here], archived [https://web.archive.org/web/20040902160534/http://www.cl.cam.ac.uk/~cwc22/hashtable/ here], with the source code available [https://github.com/davidar/c-hashtable/ here]. [[POSIX]] 1003.1-2001 describes the functions <code>hcreate()</code>, <code>hdestroy()</code> and <code>hsearch()</code></ref>
Another 3rd-party library, uthash, also creates associative arrays from C structures. A structure represents a value, and one of the structure fields serves as the key.<ref>{{cite web |title=uthash: a hash table for C structures |url=
Finally, the [[GLib]] library also supports associative arrays, along with many other advanced data types and is the recommended implementation of the GNU Project.<ref>{{cite web |title=Hash Tables |url=https://developer.gnome.org/glib/stable/glib-Hash-Tables.html |website=Gnome Developer |access-date=3 August 2020}}</ref>
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===F#===
===={{code|Map<'Key,'Value>}}====
At runtime, [[F Sharp (programming language)|F#]] provides the <code>Collections.Map<'Key,'Value></code> type, which is an immutable [[AVL tree]].
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=====Access by key=====
Values can be looked up via one of the <code>Map</code> members, such as its indexer or <code>Item</code> property (which throw an [[Exception handling|exception]] if the key does not exist) or the <code>TryFind</code> function, which returns an [[option type]] with a value of
<syntaxhighlight lang="fsharp">
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In both examples above, the <code>sallyNumber</code> value would contain the string <code>"555-9999"</code>.
===={{code|Dictionary<'TKey,'TValue>}}====
Because F# is a .NET language, it also has access to features of the [[.NET Framework]], including the {{code|System.Collections.Generic.Dictionary<'TKey,'TValue>|f#}} type (which is implemented as a [[hash table]]), which is the primary associative array type used in C# and Visual Basic. This type may be preferred when writing code that is intended to operate with other languages on the .NET Framework, or when the performance characteristics of a hash table are preferred over those of an AVL tree.
=====Creation=====
The <code>dict</code> function provides a means of conveniently creating a .NET dictionary that is not intended to be mutated; it accepts a sequence of tuples and returns an immutable object that implements
<syntaxhighlight lang="fsharp">
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