type-error-datum, type-error-expected-type

ToC

Allegro CL

ANSI Common Lisp

4 Types and Classes

4.4 Dictionary of Types and Classes

4.4.30 type-error-datum, type-error-expected-type

Function

Syntax:

type-error-datum condition

datum

type-error-expected-type condition expected-type

Arguments and Values:

condition - a condition of type type-error.

datum - an object.

expected-type - a type specifier.

Description:

type-error-datum returns the offending datum in the situation represented by the condition.

type-error-expected-type returns the expected type of the offending datum in the situation represented by the condition.

Examples:

 (defun fix-digits (condition)
   (check-type condition type-error)
   (let* ((digits '(zero one two three four
                   five six seven eight nine))
         (val (position (type-error-datum condition) digits)))
     (if (and val (subtypep 'fixnum (type-error-expected-type condition)))
         (store-value 7))))
 
 (defun foo (x)
   (handler-bind ((type-error #'fix-digits))
     (check-type x number)
     (+ x 3)))
 
 (foo 'seven)
 10

See Also:

type-error, Conditions

Allegro CL Implementation Details:

None.