eq two lists

[Jonathan Handojo]

Hi guys,

 

Can someone explain the result behind (eq '(1 2) '(1 2))?

 

I've been using the eq function quite a while and just found this out.

I can very well use equal, but this just rings a concern.

 

Thanks,

Jonathan Handojo

[Anushka]

(equal '(1 2) '( 1 2))

like this ??

 

 

 

 

 

[dlanorh]

This will give you a hint

 

(setq a '(1 2) b a)

(eq a b) => T

[Jonathan Handojo]

4 minutes ago, dlanorh said:

This will give you a hint

 

(setq a '(1 2) b a)

(eq a b) => T

 

Man that's weird... I mean normally if you want to compare between two lists, they are in most cases not gonna be in that form.

 

You normally have a list coming from one evaluation, and another list that evaluates to the exact same list (in my case, it's a list of strings) from another evaluation. Then when I run (eq a b), it evaluates to nil

[dlanorh]

basically with lists (eq ...) tests if they are bound to the same object/entity. Same applies to (= ..). However  (equal ...) tests if they evaluate to the same thing.

Edited April 2, 2020 by dlanorh

[hanhphuc]

7 hours ago, Jonathan Handojo said:

 

Man that's weird... I mean normally if you want to compare between two lists, they are in most cases not gonna be in that form.

 

You normally have a list coming from one evaluation, and another list that evaluates to the exact same list (in my case, it's a list of strings) from another evaluation. Then when I run (eq a b), it evaluates to nil

 

be careful

(setq a '(1 2) b a c a)

(eq a '(1 2) )
;nil
(eq a b)
;T

(equal '(1 2) a )
;T

(= '(1 2) a b)
;nil
(= a b c)
;T

 

Edited April 2, 2020 by hanhphuc
Jon's dizziness so '(1 2 3) -> '(1 2)

[Jonathan Handojo]

2 hours ago, dlanorh said:

basically with lists (eq ...) tests if they are bound to the same object/entity. Same applies to (= ..). However  (equal ...) tests if they evaluate to the same thing.

Makes sense now, although (eq 2 2) or (eq "str" "str") returns T.

 

2 hours ago, hanhphuc said:

 

be careful

(setq a '(1 2 3) b a c a)

(eq a '(1 2 3) )
;nil
(eq a b)
;T

(equal '(1 2 3) a )
;T

(= '(1 2 3) a b)
;nil
(= a b c)
;T

 

 

Oh, please don't make me any dizzier than I already am 

[dlanorh]

Just now, Jonathan Handojo said:

Makes sense now, although (eq 2 2) or (eq "str" "str") returns T.

 

 

I know, but 2, "str"  and any real numbers are not lists and so are evaluated.

[myloveflyer]

(eq expression 1 expression 2)
It mainly determines whether the two expressions have the same constraint conditions (whether Expression 1 and Expression 2 are set to the same object.

(setq f1 '(a b c) f2 '(a b c))
(setq f3 f2)
(eq f1 f2)   ;---->nil ,Because f1 and f2 have the same value, they do not point to the same list
(eq f3 f2)   ;---->T,Because f3 and f2 point to the same list

So I will tell you this, you should be able to understand it. In the case of not sure whether it is the same table, I generally use (equal expression 1 expression 2 [FUZZ])