
The FAILURE-MESSAGE, in the form of a string, is a unique message that will
identify this constraint if it fails. Clearly it is preferable to have the message have
some meaning for the human reader, although it need not. It does, however, need to
be recognized by a Failure Handler. The FAILURE-SUGGESTIONS are used if the
constraint fails. Notice that the suggestions include BY FAILURE-AMOUNT. The
variable FAILURE-AMOUNT will be set by the system at the time of constraint failure
to the amount by which the TEST failed. In fact, any variable or arithmetic expression
can be used after the separator BY.
The KNOWNS section of the BODY gathers al ...