The JSON format contains a value null to represent missing data. The JSON:-null symbol in Maple is used to represent JSON null symbols after import into Maple.

The commands JSON:-ParseString and JSON:-ParseFile may produce output which uses JSON:-null.

The JSON:-ToString command recognizes JSON:-null and translates it to null in JSON.

JSON:-ParseString("[2,3,null,5,null,7]");

$\left[2\,3\,\mathrm{JSON}:-\mathrm{null}\,5\,\mathrm{JSON}:-\mathrm{null}\,7\right]$

Beowulf := table([ "title" = "Beowulf", "language" = "Anglo-Saxon", "author" = JSON:-null ]);

$\mathrm{Beowulf}≔table\left(\left[''title''=''Beowulf''\,''author''=\mathrm{JSON}:-\mathrm{null}\,''language''=''Anglo-Saxon''\right]\right)$

JSON:-ToString( Beowulf );

$''\{"author":\; null,\; "language":\; "Anglo-Saxon",\; "title":\; "Beowulf"\}''$

The JSON[null] command was introduced in Maple 2015.

For more information on Maple 2015 changes, see Updates in Maple 2015.