6 Iteration 6.1 The LOOP Facility 6.1.1 Overview of the Loop Facility 18.104.22.168 Summary of Loop Clauses
22.214.171.124.3 Summary of Termination Test ClausesThe for and as constructs provide a termination test that is determined by the iteration control clause.
The repeat construct causes termination after a specified number of iterations. (It uses an internal variable to keep track of the number of iterations.)
The until construct is the inverse of while;
it terminates the iteration if the test evaluates to
any non-nil value.
An until clause is equivalent to the expression
The thereis construct takes one form and terminates the loop if the form ever evaluates to a non-nil object; in this case, the loop form returns that object. Otherwise, it provides a default return value of nil.
For more information, see Section 6.1.4 Termination Test Clauses.