The call type(a, type) checks to see if a is a valid type expression. By definition, a type expression is any expression a for which the command type(expr, a) could succeed.

A type defined by the system (such as integer, numeric, and name), a type defined by a procedure (`type/a`), a type defined by an assignment, or a combination of types are valid type expressions.

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

$\mathrm{true}$

$\mathrm{type}\left(a\,\mathrm{type}\right)$

$\mathrm{false}$

$\mathrm{type}\left(\mathrm{name}=\mathrm{numeric}..\mathrm{numeric}\,\mathrm{type}\right)$

$\mathrm{true}$

$\mathrm{mytype}≔\left\{\mathrm{integer}\,\mathrm{list}\,\mathrm{name}\right\}$

$\mathrm{mytype}≔\left\{\mathrm{integer}\,\mathrm{list}\,\mathrm{name}\right\}$

$\mathrm{type}\left(\mathrm{mytype}\,\mathrm{type}\right)$

$\mathrm{true}$