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The difference is that there are two evaluations in (eval '(a b)). When you type (eval '(a b)) into the repl, the call to READ in the repl turns the string '(a b) into the form (quote (a b)), and the call to EVAL (still in the repl) evaluates the quote form and returns the list (a b). Now your expli...

A (setf if) macro would be nice, so you can say

gaitdoctor wrote:I AM TRUELY A NEWBIE.... THE GUYS WHO GET IT EASY, DON'T GET IT WHY SOME DON'T.

WHAT ARE YOU HAVING TROUBLE WITH?

I have just entered the world of LISP so I'm a bit of a newbie! Welcome 8-) I want to change a list containing something like (2 x + 1) into something like (2 x) i.e. I want to find and delete all (+ 1)s in a list. Walk down the list, checking each cdr (ie. remainder) of the list to see if it start...

(defun set-adj (x y) (setf (gethash x Breadth-info) y) ) (defun get-adj (x) (gethash x Breadth-info) ) (set 'A '(B C)) (defun successors (n) (get-adj n) ) You're never calling SET-ADJ, so GET-ADJ is returning NIL. This seems to work with the rest of your implementation: (defun successors (n) (symbo...

how can i use the defmacro in order to simplify any given polynomial e.g (x + y)(x + y) → x2 + 2xy + y2 There's some code here . You don't need a macro if you're doing the simplification at runtime. You just quote the arguments, as in (simplify '(* (+ x 1) (+ x -1))). Once a product is expanded, ...

There are a couple simple reader macros here . One is a sort of multi-purpose infix/postfix/message-passing syntax, and the other one fakes partial function application. There are more macros in the standard library and the pattern-matching library that are linked from that page, but non-Lispers see...

(defun hello (x) (setf x 6)) (setf y 3) (hello y) How can I make it so that so that the value of y is changed to 6??? This operates on a place, so it would be a macro: CL-USER> (defmacro setf-6 (place) `(setf ,place 6)) SETF-6 CL-USER> (let ((x 3)) (setf-6 x) x) 6

If you're only using B as a boolean, you should write (and a b).

In the macro chapter of Ansi common lisp it's explained that using string list manipulation and eval to create macro like behavior, such as I suggested, is almost never used, because 1) doing it that way doesn't allow the use of lexical content, and 2) making eval compile or interpret a raw list is...