The IsTree(expr) command tests whether a Maple expression expr is an XML tree data structure. If expr is an XML tree data structure, the value true is returned.  Otherwise, false is returned.

Note: A full recursive traversal of the input is performed, so this is an extremely expensive test.

$\mathrm{with}\left(\mathrm{XMLTools}\right)\:$

$\mathrm{IsTree}\left(\mathrm{XMLElement}\left(''a''\,\left[''b''=''c''\right]\,''d''\,\mathrm{XMLElement}\left(''foo''\,\left[''colour''=''red''\right]\,''bar''\right)\right)\right)$

$\mathrm{true}$