The Exists command returns true if a type is associated with the name typename via the TypeTools package, and false otherwise.

Note that the Exists command does not check whether a name is the name of a valid type, since built-in types and types created by assigning to the name type/typename are not recognized.

To determine whether a name is the name of a valid type, use type( typename, 'type' ).

$\mathrm{TypeTools}\left[\mathrm{AddType}\right]\left('\mathrm{tff}'\,'\left\{\mathrm{identical}\left(\mathrm{FAIL}\right)\,\mathrm{identical}\left(\mathrm{false}\right)\,\mathrm{identical}\left(\mathrm{true}\right)\right\}'\right)$

$\mathrm{TypeTools}\left[\mathrm{Exists}\right]\left('\mathrm{tff}'\right)$

$\mathrm{true}$

$\mathrm{TypeTools}\left[\mathrm{Exists}\right]\left('\mathrm{no\_such\_type\_\_}'\right)$

$\mathrm{false}$

$\mathrm{TypeTools}\left[\mathrm{Exists}\right]\left('\mathrm{integer}'\right)$

$\mathrm{false}$

$\mathrm{type}\left('\mathrm{integer}'\,'\mathrm{type}'\right)$

$\mathrm{true}$