9 Conditions  9.1 Condition System Concepts 9.1.3 Printing Conditions 9.1.3.1 Recommended Style in Condition Reporting
9.1.3.1.3 Embedded Newlines in Condition Reports
Especially if it is long, it is permissible and appropriate for
a report message to contain one or more embedded newlines.
If the calling routine conventionally inserts some additional prefix
(such as "Error: " or ";; Error: ") on the first line of
the message, it must also assure that an appropriate prefix will be
added to each subsequent line of the output, so that the left edge of
the message output by the condition reporter will still be properly
aligned.
(defun test ()
(error "This is an error message.~%It has two lines."))
;; Implementation A
(test)
This is an error message.
It has two lines.
;; Implementation B
(test)
;; Error: This is an error message.
;; It has two lines.
;; Implementation C
(test)
>> Error: This is an error message.
It has two lines.
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