Common Lisp中的eq，eql，equal和equip有什么区别？ [英] What's the difference between eq, eql, equal and equalp, in Common Lisp?
问题描述
eq ， eql ，等于和 equalp ，在Common Lisp中？我了解其中有些检查类型，有些检查所有类型，但是哪一个呢？什么时候比另一个更好？
What's the difference between eq, eql, equal and equalp, in Common Lisp? I understand that some of them check types, some of them check across types an all that, but which is which? When is one better to use than the others?
推荐答案
（eq xy）为真，当且仅当x和y是相同的对象。
(eq x y)is true if and only ifxandyare the same identical object.
eql 谓词为真，如果其参数为 eq ，或者它们是具有相同值的相同类型的数字，或者它们是表示相同字符的字符对象。
The eql predicate is true if its arguments are eq, or if they are numbers of the same type with the same value, or if they are character objects that represent the same character.
如果其参数是结构相似（同构）的对象，则equal 谓词为true。一条粗略的经验法则是，当且仅当它们的打印表示形式相同时，两个对象才相等。
The equal predicate is true if its arguments are structurally similar (isomorphic) objects. A rough rule of thumb is that two objects are equal if and only if their printed representations are the same.
两个对象是 equalp 如果它们相等；如果它们是字符并且满足字符相等，则忽略字母大小写和字符的某些其他属性；如果它们是数字并且具有相同的数值，即使它们是不同的类型；或如果它们都具有 equalp 。
Two objects are equalp if they are equal; if they are characters and satisfy char-equal, which ignores alphabetic case and certain other attributes of characters; if they are numbers and have the same numerical value, even if they are of different types; or if they have components that are all equalp.
以下是同一页面上的一些示例我链接到上面：
Here are some examples from the same page I linked to above:
(eq 'a 'b) is false.
(eq 'a 'a) is true.
(eq 3 3) might be true or false, depending on the implementation.
(eq 3 3.0) is false.
(eq 3.0 3.0) might be true or false, depending on the implementation.
(eq #c(3 -4) #c(3 -4))
might be true or false, depending on the implementation.
(eq #c(3 -4.0) #c(3 -4)) is false.
(eq (cons 'a 'b) (cons 'a 'c)) is false.
(eq (cons 'a 'b) (cons 'a 'b)) is false.
(eq '(a . b) '(a . b)) might be true or false.
(progn (setq x (cons 'a 'b)) (eq x x)) is true.
(progn (setq x '(a . b)) (eq x x)) is true.
(eq #\A #\A) might be true or false, depending on the implementation.
(eq "Foo" "Foo") might be true or false.
(eq "Foo" (copy-seq "Foo")) is false.
(eq "FOO" "foo") is false.
(eql 'a 'b) is false.
(eql 'a 'a) is true.
(eql 3 3) is true.
(eql 3 3.0) is false.
(eql 3.0 3.0) is true.
(eql #c(3 -4) #c(3 -4)) is true.
(eql #c(3 -4.0) #c(3 -4)) is false.
(eql (cons 'a 'b) (cons 'a 'c)) is false.
(eql (cons 'a 'b) (cons 'a 'b)) is false.
(eql '(a . b) '(a . b)) might be true or false.
(progn (setq x (cons 'a 'b)) (eql x x)) is true.
(progn (setq x '(a . b)) (eql x x)) is true.
(eql #\A #\A) is true.
(eql "Foo" "Foo") might be true or false.
(eql "Foo" (copy-seq "Foo")) is false.
(eql "FOO" "foo") is false.
(equal 'a 'b) is false.
(equal 'a 'a) is true.
(equal 3 3) is true.
(equal 3 3.0) is false.
(equal 3.0 3.0) is true.
(equal #c(3 -4) #c(3 -4)) is true.
(equal #c(3 -4.0) #c(3 -4)) is false.
(equal (cons 'a 'b) (cons 'a 'c)) is false.
(equal (cons 'a 'b) (cons 'a 'b)) is true.
(equal '(a . b) '(a . b)) is true.
(progn (setq x (cons 'a 'b)) (equal x x)) is true.
(progn (setq x '(a . b)) (equal x x)) is true.
(equal #\A #\A) is true.
(equal "Foo" "Foo") is true.
(equal "Foo" (copy-seq "Foo")) is true.
(equal "FOO" "foo") is false.
(equalp 'a 'b) is false.
(equalp 'a 'a) is true.
(equalp 3 3) is true.
(equalp 3 3.0) is true.
(equalp 3.0 3.0) is true.
(equalp #c(3 -4) #c(3 -4)) is true.
(equalp #c(3 -4.0) #c(3 -4)) is true.
(equalp (cons 'a 'b) (cons 'a 'c)) is false.
(equalp (cons 'a 'b) (cons 'a 'b)) is true.
(equalp '(a . b) '(a . b)) is true.
(progn (setq x (cons 'a 'b)) (equalp x x)) is true.
(progn (setq x '(a . b)) (equalp x x)) is true.
(equalp #\A #\A) is true.
(equalp "Foo" "Foo") is true.
(equalp "Foo" (copy-seq "Foo")) is true.
(equalp "FOO" "foo") is true.
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