The Common Lisp Condition System by Michał “phoe” Herda

Author:Michał “phoe” Herda
Language: eng
Format: epub
ISBN: 9781484261347
Publisher: Apress

Note that our macro needed to expand into a progn in order to accommodate more than one generated form. We can see that the superclass list in defclass now contains the name of the condition class and that the :report option has been rendered into its separate print-object method . In addition, we return the name of the condition from the final form, as dictated by the Common Lisp standard.

For clarity, we will separate our macro into two logical parts. The first will be a function named define-condition-make-report-method that will be used for generating the defmethod print-object form .(defun define-condition-make-report-method (name report-option)

(let* ((condition (gensym "CONDITION"))

(stream (gensym "STREAM"))

(report (second report-option))

(report-form (if (stringp report)

`(write-string ,report ,stream)

`(funcall #',report ,condition ,stream))))

`(defmethod print-object ((,condition ,name) ,stream)

,report-form)))

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