CODEWITHSUNDEEP
lispelispcommon-lisp
anothertest
anothertest

Reputation: 979

Modify list and return it inside a function in lisp

(defun testthis (node index newvalue)
  (set-nth node index newvalue)
   node
)

I would like to modify the nth element of a list in a function and then returns this list to save the modification performed.

How can I do a such function in lisp?

Upvotes: 0

Views: 416

Answers (1)

Sylwester
Sylwester

Reputation: 48745

You can use setf and the nth accessor: 

(defun replace-index (node index new-value)
   (setf (nth index node) new-value)
   node)

(defparameter *orig* (list 1 2 3 4))
(defparameter *mod* (replace-index *orig* 2 99))
(list *orig* *mod*) ; ==> ((1 2 99 4) (1 2 99 4))

Upvotes: 2

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