Skip to main content

simple-type-error

simple-type-error Condition Type

Class Precedence List:

simple-type-error, simple-condition, type-error, error, serious-condition, condition, t

Description:

Conditions of type simple-type-error are like conditions of type type-error, except that they provide an alternate mechanism for specifying how the condition is to be reported; see the type simple-condition.

See Also:

simple-condition, simple-condition-format-control, simple-condition-format-arguments, type-error-datum, type-error-expected-type

Expanded Reference: simple-type-error​

Signaling a simple-type-error​

simple-type-error is a condition type that combines type-error and simple-condition. It supports both type-error slots (:datum, :expected-type) and a format control string.

(handler-case
    (error 'simple-type-error
           :datum "hello"
           :expected-type 'integer
           :format-control "Expected ~A but got ~S"
           :format-arguments '(integer "hello"))
  (simple-type-error (c)
    (format nil "~A" c)))
=> "Expected INTEGER but got \"hello\""

Accessing Both Sets of Slots​

(handler-case
    (error 'simple-type-error
           :datum 3.14
           :expected-type 'integer
           :format-control "~S is not an integer"
           :format-arguments '(3.14))
  (simple-type-error (c)
    (list :datum (type-error-datum c)
          :expected (type-error-expected-type c)
          :message (simple-condition-format-control c))))
=> (:DATUM 3.14 :EXPECTED INTEGER :MESSAGE "~S is not an integer")