
assert(+Clause)

   Add specified clause at the end of the dynamic procedure to the database.



Arguments
   Clause              Atom or compound term

Type
   Dynamic Predicates

Description
   Adds the specified clause for a dynamic procedure to the database.  The
   clause is added AFTER any existing clauses for the procedure.


   The procedure must be declared to be dynamic using the dynamic/1
   built-in.  If the procedure is undefined an exception is raised.
   However, the default error handler for this exception simply declares
   the procedure dynamic and asserts the clause.


   The asserted clause is NOT removed from the database on backtracking
   through the call to assert/1.


   assert/1 satisfies the logical update semantics.  Asserting a clause to
   a procedure will not, in any way, affect previous calls to it when
   backtracking.




Modes and Determinism
   assert(+) is det

Modules
   This predicate is sensitive to its module context (tool predicate, see @/2).

Exceptions
     4 --- Clause is a free variable.
     4 --- The head of Clause is a free variable.
     5 --- Clause is not a valid Prolog clause.
    63 --- The procedure is not dynamic.
    70 --- The procedure is undefined.  However, the default error    handler for this exception simply declares the procedure dynamic and    asserts the clause, if the error was caused by an assert.

Examples
      Success:
    assert(city(munich)).
    assert((likes(X,Y):-man(X),woman(Y)).

   Error:
    assert(X).                        - gives error 4.
    assert("the man").                - gives error 5.
    assert(1).                        - gives error 5.
    assert((my_static(X):-write(X))). - gives error 63.
                                        if my_static/1 is not
                                        dynamic.
   Logical semantics :

   If the following clauses are in the database :
p :- assert(p), fail.
p :- fail.

q :- fail.
q :- assert(q), fail.

   The queries p.  and q.  will both fail.





See Also
   dynamic / 1, asserta / 1, retract / 1, compile_term / 1
