lisp

I am working using a visual programming environment for musical composition based on CL . I am trying to create a function that when given say 3 elements (1 2 3) will return 1, 2, 3, 1, 2, 3 etc., one number at the time each time it is evaluated. The book Common Lisp a Gentle Introduction , mentions briefly that it's possible to create circular lists using sharp-equal notation but does not get into details on how to use them. Keep in mind that I can insert actual Lisp code in the program using a object specifically designed for that. CL-USER 3 > (defun circular (items) (setf (cdr (last items))

Anybody know what #+ and #- operators means in .sbclrc ? I couldn't find it in the manual. I see #- in .sbclrc after I installed quicklisp: #-quicklisp (let ((quicklisp-init (merge-pathnames "quicklisp/setup.lisp" (user-homedir-pathname)))) (when (probe-file quicklisp-init) (load quicklisp-init))) I also see #+ in the SBCL User Manual, but I couldn't find explanation of their functionality. Looks like something related for loading individual module. Are they only for SBCL implementation or part of Common lisp? That's a general facility of Common Lisp, not only SBCL. There is a variable cl:

read-line and read-char both require you press Enter key after typing something. Is there any mechanism in Common Lisp that would allow the program to continue upon the press of any single character immediately, without requiring the additional step of pressing Enter? I'm trying to build a quick, dynamic text input interface for a program so users can quickly navigate around and do different things by pressing numbers or letters corresponding to onscreen menus. All the extra presses of the Enter key seriously interrupt the workflow. This would also be similar to a "y/n" type of interrogation

I am trying to learn lisp, using emacs dialect and I have a question. let us say list has some members, for which predicate evaluates to false. how do I create a new list without those members? something like { A in L: p(A) is true } . in python there is filter function, is there something equivalent in lisp? if not, how do I do it? Thanks rootzlevel These functions are in the CL package, you will need to (require 'cl) to use them: (remove-if-not #'evenp '(1 2 3 4 5)) This will return a new list with all even numbers from the argument. Also look up delete-if-not , which does the same, but

I am trying to transpose a list of lists; my comments indicate the thought process. (setq thingie '((1 2 3) (4 5 6) (7 8 9))) ;;test case (defun trans (mat) (if (car mat) (let ((top (mapcar 'car mat)) ;;slice the first row off as a list (bottom (mapcar 'cdr mat))) ;;take the rest of the rows (cons top (trans bottom)))) ;;cons the first-row-list with the next-row-list mat) (trans thingie) => ((1 2 3) (4 5 6) (7 8 9)) ;;wait what? But, I really want it to be ((1 4 7) (2 5 8) (3 6 9)) What am I doing wrong? There is a simple way for this: (defun rotate (list-of-lists) (apply #'mapcar #'list list