Define n functions at once in Lisp

Suppose I want to do the following:

(loop for i from 1 to n do
    (defun ith(lst)
        (nth i lst)))

Apparently what I really want to do is the following:

(defun 1th(lst)(nth 1 lst))
(defun 2th(lst)(nth 2 lst))
(defun 3th(lst)(nth 3 lst))
(defun 4th(lst)(nth 4 lst))
......
(defun 100th(lst开发者_如何学Go)(nth 100 lst))

How can I make that?

---

Here you go. Note that |1th| would return the second value:

(defmacro make-nths (n)
  `(progn
     ,@(loop for i from 1 to n
             collecting `(defun ,(intern (format nil "~ath" i)) (list)
                           (nth ,i list)))))

As Xach pointed out in the comments, macrolet might be preferable here, since you do not really need a globally defined macro:

(macrolet ((make-nths (n)
             `(progn
                ,@(loop for i from 1 to n
                        collect `(defun ,(intern (format nil "~ath" i)) (list)
                                   (nth ,i list))))))
  (make-nths 3)) ; choose n here

Finally, here is a working version of ninjaaa's non-macro solution:

(loop for i from 1 to 3 ; choose n here
      do (let ((i i))   ; introduce new bindings for each iteration
           (setf (symbol-function (intern (format nil "~ath" i)))
                 (lambda (list) (nth i list)))))

---

Try this:

(loop for i from 1 to n do
   (setf (symbol-function (intern (format nil "~dth" i)))
     #'(lambda (lst) (nth i lst))))