A number of the functions in the condition system take arguments which are identified as condition designators. By convention, those arguments are notated as
datum &rest arguments
Taken together, the datum and the arguments are ``designators for a condition of default type default-type.'' How the denoted condition is computed depends on the type of the datum:
(apply #'make-condition datum arguments)
(make-condition defaulted-type :format-control datum :format-arguments arguments)
where the defaulted-type is a subtype of default-type.
Note that the default-type gets used only in the case where the datum string is supplied. In the other situations, the resulting condition is not necessarily of type default-type.
Here are some illustrations of how different condition designators can denote equivalent condition objects:
(let ((c (make-condition 'arithmetic-error :operator '/ :operands '(7 0)))) (error c)) == (error 'arithmetic-error :operator '/ :operands '(7 0)) (error "Bad luck.") == (error 'simple-error :format-control "Bad luck." :format-arguments '())