4

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.

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2 Answers 2

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

Personally I prefer quasiquotes for this: `(the answer is ,n).
@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?
@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.
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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.

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