CLCS
src report error
Index
method-combination-error Conditions Dictionary simple-condition
Function

signal

signal datum &rest arguments ⇒ nil

Arguments and Values

datum, argumentsdesignators for a condition of default type simple-condition.

Description

Signals the condition denoted by the given datum and arguments. If the condition is not handled, signal returns nil.

Examples

 (defun handle-division-conditions (condition)
   (format t "Considering condition for division condition handling~
   (when (and (typep condition 'arithmetic-error)
              (eq '/ (arithmetic-error-operation condition)))
     (invoke-debugger condition)))
HANDLE-DIVISION-CONDITIONS
 (defun handle-other-arithmetic-errors (condition)
   (format t "Considering condition for arithmetic condition handling~
   (when (typep condition 'arithmetic-error)
     (abort)))
HANDLE-OTHER-ARITHMETIC-ERRORS
 (define-condition a-condition-with-no-handler (condition) ())
A-CONDITION-WITH-NO-HANDLER
 (signal 'a-condition-with-no-handler)
NIL
 (handler-bind ((condition #'handle-division-conditions)
                  (condition #'handle-other-arithmetic-errors))
   (signal 'a-condition-with-no-handler))
Considering condition for division condition handling
Considering condition for arithmetic condition handling
NIL
 (handler-bind ((arithmetic-error #'handle-division-conditions)
                  (arithmetic-error #'handle-other-arithmetic-errors))
   (signal 'arithmetic-error :operation '* :operands '(1.2 b)))
Considering condition for division condition handling
Considering condition for arithmetic condition handling
Back to Lisp Toplevel

Side Effects

The debugger might be entered due to *break-on-signals*.

Handlers for the condition being signaled might transfer control.

Affected By

Existing handler bindings.

*break-on-signals*

See Also

*break-on-signals*, error, simple-condition, Signaling and Handling Conditions

Notes

If (typep datum *break-on-signals*) yields true, the debugger is entered prior to beginning the signaling process. The continue restart can be used to continue with the signaling process. This is also true for all other functions and macros that should, might, or must signal conditions.

Backlinks

*break-on-signals*, Condition System Concepts, Conditions Dictionary, Creating Conditions, error, handler-bind, Resignaling a Condition, restart-case, Serious Conditions, serious-condition, Signaling, simple-condition, Symbols in the COMMON-LISP Package, warn