问题
From reading introductory material on Lisp, I now consider the following to be identical:
(list 1 2 3)
'(1 2 3)
However, judging from problems I face when using the quoted form in both Clojure and Emacs Lisp, they are not the same. Can you tell me what the difference is?
回答1:
The primary difference is that quote prevents evaluation of the elements, whereas list
does not:
user=> '(1 2 (+ 1 2)) (1 2 (+ 1 2)) user=> (list 1 2 (+ 1 2)) (1 2 3)
For this reason (among others), it is idiomatic clojure to use a vector when describing a literal collection:
user=> [1 2 (+ 1 2)] [1 2 3]
回答2:
Quoted lists (e.g. '(1 2 3)) should be treated carefully (generally as read-only). (see SO answers When to use 'quote in Lisp and When to use 'quote in Lisp).
(list 1 2 3) will "cons" up a fresh list, independent of all others.
You can see an example of a pitfall of using quoted lists in the manual for nconc.
And, as you probably know, when you call 'list - the arguments will obviously be evaluated versus the contents of a quoted list. And 'quote takes a single argument, versus 'lists variable number of arguments.
(list (+ 1 2) 3) --> (3 3)
(quote ((+ 1 2) 3)) --> ((+ 1 2) 3)
回答3:
In Common Lisp, quoted objects are constant literal data. You should not modify this data, as the consequences are undefined. Possible consequences are: modification of shared data, attempt to modify read-only data, an error might be signalled, it might just work, ...
For lists:
'(1 2 3)
Above is a constant list, which will be constructed by the reader and evaluating to itself, because it is quoted. If it appears in Lisp code, a compiler will embed this data somehow in the FASL code.
(quote (1 2 3)) is another way to write it.
(list 1 2 3)
this is a call of the Common Lisp function LIST with three arguments 1, 2 and 3. When evaluated the result is a fresh new list (1 2 3).
Similar:
'(1 . 2) and (cons 1 2)
'#(1 2 3) and (vector 1 2 3)
One is the literal data and the other is a function call that constructs such a data structure.
来源：https://stackoverflow.com/questions/3896542/in-lisp-clojure-emacs-lisp-what-is-the-difference-between-list-and-quote