The assert action allows the user to add a fact to the fact-list. Multiple facts may be asserted with each call. If the facts item is being watched (see section 13.2), then an informational message will be printed each time a fact is asserted.
Syntax
(assert <RHS-pattern>+)
Missing slots in a template fact being asserted are assigned their default value (see section 3). If an identical copy of the fact already exists in the fact-list, the fact will not be added (however, this behavior can be changed, see sections 13.4.4 and 13.4.5). Note that in addition to constants, expressions can be placed within a fact to be asserted. The first field of a fact must be a symbol. The value returned of the assert function is the fact-address of the last fact asserted. If the assertion of the last fact causes an error, or if an identical copy of the fact already exists in the fact-list, then the symbol FALSE is returned.
Example
CLIPS> (clear)
CLIPS> (assert (color red))
<Fact-0>
CLIPS> (assert (color blue) (value (+ 3 4)))
<Fact-2>
CLIPS> (assert (color red))
FALSE
CLIPS> (deftemplate status (slot temp) (slot pressure))
CLIPS> (assert (status (temp high)
(pressure low)))
<Fact-3>
CLIPS> (facts)
f-0 (color red)
f-1 (color blue)
f-2 (value 7)
f-3 (status (temp high) (pressure low))
For a total of 4 facts.
CLIPS>