Lisp initialize variable with list

Question

I'm learning Lisp. I'm implementing solution to some relatively simple problem. I'm thinking of list that represents initial state of problem like this

((0 1) (2 3) (5 4))

I want to create variable and assign that list to it. I've tried

(let ((initial-state ((0 1) (2 3) (5 4)))))

but this won't compile. After that I've tried

(let ((initial-state list (list 0 1) (list 2 3) (list 5 4))))

this works, but it's too long. Is there better way to do this?

score 5 · Answer 1 · answered Dec 23 '11 at 13:26

5

(let ((initial-state '((0 1) (2 3) (4 5))))
  ...)

The ' expands to (quote ...) which basically means "don't evaluate this, just return it to me as a list". It's used to separate data from code (which in lisp are related concepts).

answered Dec 23 '11 at 13:26

mange

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score 3 · Accepted Answer · edited May 23 '17 at 11:48

3

Do you mean this?

(let ((initial-state '((0 1) (2 3) (5 4)))) ...)

That single quote is a quote. :) More about quoting here:

edited May 23 '17 at 11:48

Community

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answered Dec 23 '11 at 13:24

Elias Dorneles

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Did you forget some parentheses? – mange Dec 23 '11 at 13:33
What lisp are you working in? `let` in Common Lisp doesn't work like that, nor does Scheme's. – mange Dec 23 '11 at 13:39

Lisp initialize variable with list

2 Answers2