lisp

问题 Peter Norvig's PAIP book contains this code as a solution to the permutation problem (some sections are removed for brevity) (defun permutations (bag) ;; If the input is nil, there is only one permutation: ;; nil itself (if (null bag) '(()) ;; Otherwise, take an element, e, out of the bag. ;; Generate all permutations of the remaining elements, ;; And add e to the front of each of these. ;; Do this for all possible e to generate all permutations. (mapcan #'(lambda (e) (mapcar #'(lambda (p)

问题 I use paredit on emacs with SLIME's repl. This means that at any point during my typing on the repl, my s-expressions are balanced. However, they may not be complete, and I might want to continue typing inside them in another line, as follows: CL-USER> (defun print-hello () ) When I start a new line by pressing the enter key, however, the SLIME repl executes my incomplete expression. I want it to wait for me to complete the expression, as follows: CL-USER> (defun print-hello () (format t

问题 I use paredit on emacs with SLIME's repl. This means that at any point during my typing on the repl, my s-expressions are balanced. However, they may not be complete, and I might want to continue typing inside them in another line, as follows: CL-USER> (defun print-hello () ) When I start a new line by pressing the enter key, however, the SLIME repl executes my incomplete expression. I want it to wait for me to complete the expression, as follows: CL-USER> (defun print-hello () (format t

问题 As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance. Closed 8 years ago . What is a good book or tutorial to learn Lisp? 回答1: Practical Common Lisp is an awesome (and free) book for anyone interested in the

问题 This is a followup to my previous post here I've a 2D geometry created using the following code, ref. (defun graph ( pts sls tls ) ( (lambda ( l ) (foreach x l (text (cdr x) (itoa (car x)) 0.0 1)) (mapcar '(lambda ( a b / p q r ) (setq p (cdr (assoc a l)) q (cdr (assoc b l)) r (angle p q) ) (entmake (list '(0 . "LINE") (cons 10 p) (cons 11 q) '(62 . 8))) (text (mapcar '(lambda ( x y ) (/ (+ x y) 2.0)) p q) (rtos (distance p q) 2) (if (and (< (* pi 0.5) r) (<= r (* pi 1.5))) (+ r pi) r) 2 ) )

问题 My question is: how to write a procedure that utilises tailcall, and that constructs a list not in the reverse order. To show what I mean, here is an example of a very simple procedure that is iterative, and that creates a copy of a list: (define (copy-list ls) (define (iter cp-ls rest-ls) (if (null? rest-ls) cp-ls (iter (cons (car rest-ls) cp-ls) (cdr rest-ls)))) (iter '() ls)) The problem is that, due to the iterative order in which the elements are cons ed together, the returned list ends

问题 My question is: how to write a procedure that utilises tailcall, and that constructs a list not in the reverse order. To show what I mean, here is an example of a very simple procedure that is iterative, and that creates a copy of a list: (define (copy-list ls) (define (iter cp-ls rest-ls) (if (null? rest-ls) cp-ls (iter (cons (car rest-ls) cp-ls) (cdr rest-ls)))) (iter '() ls)) The problem is that, due to the iterative order in which the elements are cons ed together, the returned list ends

问题 I'm going through SICP course and as recommended installed mit-scheme. I want to use the REPL together with a scheme file. The reason is because I can add scheme code in the file and then run the commands in REPL. What I have works, but the problem is every time I edit the file, I have to quit terminal and reload the file for REPL to see changes. Is there a way to reload the file easily or some other way for REPL to see changes from the file? This my setup: I installed mit-scheme with brew

问题 I've looked at all of the similar questions on stack overflow. This one is different enough to warrant a separate question. Basically, I can't start a repl server because I get the error below. It's been pointed out that this is typically a dependency issue, but I'm updated, to my knowledge. What am I getting wrong here? Here's the full error: error in process sentinel: Could not start nREPL server: java.lang.NumberFormatException: Invalid number: 0.8.3 at clojure.lang.LispReader.readNumber

问题 I've found some techniques in other SO answers, but apparently I've been unable to convince SBCL to do inline fixnum arithmetic: (declaim (optimize (speed 2) (safety 1))) (declaim (ftype (function (fixnum fixnum) double-float) fixnumtest) (inline fixnumtest)) (defun fixnumtest (i j) (declare (type fixnum i j)) (let* ((n (the fixnum (+ i j))) (n+1 (the fixnum (1+ n)))) (declare (type fixnum n n+1)) (/ 1.0d0 (the fixnum (* n n+1)) ) ) ) (defun main () (format t "~11,9F~%" (fixnumtest 2 3)) )