In my quest to fully understand the so powerful lisp macros a question came to my mind. I know that a golden rule about macros is the one saying "Never use a macro when a function will do the work". However reading Chapter 9 - Practical: Building a Unit Test Framework - from the book Practical Common Lisp I was introduced to the below macro whose purpose was to get rid of the duplication of the test case expression, with its attendant risk of mislabeling of results.
;; Function defintion.
(defun report-result (result form)
(format t "~:[FAIL~;pass~] ... ~a~%" result form))
;; Macro Definition
(defmacro check (form)
`(report-result ,form ',form))
OK, I understand its purpose but I could have done it using a function instead of a macro, for instance:
(setf unevaluated.form '(= 2 (+ 2 3)))
(defun my-func (unevaluated.form)
(report-result (eval unevaluated.form) unevaluated.form))
- Is this only possible because the given macro is too simple ?
- Furthermore, is Lisp Macro System so powerful relatively its opponents due to the code itself - like control structures, functions, etc - is represented as a LIST ?