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9.1.1 Condition Types

The next figure lists the standardized condition types. Additional condition types can be defined by using define-condition.

arithmetic-error floating-point-overflow simple-type-error
cell-error floating-point-underflow simple-warning
condition package-error storage-condition
control-error parse-error stream-error
division-by-zero print-not-readable style-warning
end-of-file program-error type-error
error reader-error unbound-slot
file-error serious-condition unbound-variable
floating-point-inexact simple-condition undefined-function
floating-point-invalid-operation simple-error warning

Figure 9.1: Standardized Condition Types

All condition types are subtypes of type condition. That is, 

 (typep c 'condition) → true

if and only if c is a condition.

Implementations must define all specified subtype relationships. Except where noted, all subtype relationships indicated in this document are not mutually exclusive. A condition inherits the structure of its supertypes.

The metaclass of the class condition is not specified. Names of condition types may be used to specify supertype relationships in define-condition, but the consequences are not specified if an attempt is made to use a condition type as a superclass in a defclass form.

The next figure shows operators that define condition types and creating conditions.

define-condition make-condition

Figure 9.2: Operators that define and create conditions.

The next figure shows operators that read the value of condition slots.

arithmetic-error-operands simple-condition-format-arguments
arithmetic-error-operation simple-condition-format-control
cell-error-name stream-error-stream
file-error-pathname type-error-datum
package-error-package type-error-expected-type
print-not-readable-object unbound-slot-instance

Figure 9.3: Operators that read condition slots.

9.1.1.1 Serious Conditions

A serious condition is a condition serious enough to require interactive intervention if not handled. Serious conditions are typically signaled with error or cerror; non-serious conditions are typically signaled with signal or warn.