variables in lisp programming

Question

I am trying to write a function lets say A(n)

which is supposed to have a list

(the answer is n)

n being any integer in the list I want when i type (A 4)

it should display (the answer is 4)

I am not sure how to go about it thinking of using setq and the list function

But how to construct it its confusing me I'm just a newbie trying to learn lisp, any ideas or books I can read I will greatly appreciate.

Peter Lundgren · Accepted Answer · 2012-10-08T18:19:39.253

4

(defun A (n) 
  (list 'the 'answer 'is n))
(A 4)
=> (the answer is 4)

edited Oct 08 '12 at 18:19

answered Oct 08 '12 at 18:06

Peter Lundgren

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Personally I prefer quasiquotes for this: `\`(the answer is ,n)`. – C. K. Young Oct 08 '12 at 18:28
1

@ChrisJester-Young It must be mentioned that in this way fuction can return literal conses. For example, if code is `(,n is what the answer is) And this can cause non obvious bugs. See [Why does this mapcan cause my REPL to freeze?](http://stackoverflow.com/questions/20207041/why-does-this-mapcan-cause-my-repl-to-freeze) – Menschenkindlein Dec 06 '13 at 16:40
@Menschenkindlein Of course, the same caveats apply as when deciding whether to use `list`/`cons` or literals. Since I'm a Schemer, my habit is to return immutable data by default, and only enabling mutability on a case-by-case basis. Certainly I do not mutate objects returned by other functions unless it's expressly documented as being a fresh instance or otherwise okay to mutate. – C. K. Young Dec 06 '13 at 17:07

score 0 · Answer 2 · answered Dec 09 '13 at 10:55

Another part of your question is what books to read. Usually people recommend to read the "Practical Common Lisp", a book with a friendly and easy-to-read introduction to the Common Lisp. Then there is the "Getting Started" article on Cliki.net. This should be sufficient to get started with the language.

variables in lisp programming

2 Answers2