3 ms·
My Lisp-fu is lower than the expected for this exercice. But it seems that you have to create a recursive function not a recursive macro, which is what you are
by edu 19y ago
My Lisp-fu is lower than the expected for this exercice. But it seems that you have to create a recursive function not a recursive macro, which is what you are doing.
Maybe the macro has to define a new recursive function that recurses until need, and then call it?
- ken 19y agoYes, I believe local functions are usually defined with flet.
- deleted 19y ago[deleted]
- paul_reiners 19y agoI'm not sure, but I think you need to use labels, rather than flet, in this case, since local functions defined using flet cannot be recursive. At least that's how I interpret what it says on page 319. At any rate, this solution works using labels: (defmacro ntimes (n &rest body) (let ((h (gensym)) (g (gensym))) `(let ((,h ,n)) (labels ((ntimes-local (,g) (if (> ,g 0) ,@body) (if (zerop ,g) nil (ntimes-local (1- ,g))))) (ntimes-local ,h))))) (Sorry, but again I don't know how to preserve the formatting of my code in this newsgroup.)
- pg 19y agohttp://news.ycombinator.com/formatdoc http://news.ycombinator.com/formatdoc
- deleted 19y ago[deleted]