What is the correct represention of (a (b . c) d) in box notation?
I am doing the exercises in Paul Graham's ANSI Common Lisp. And I have had a key to the exercises by other person, which is:
http://www.shido.info/lisp/pacl2_e.html
After having finished the exercises for Chapter 3, I refer to that key to check my answers one by one. When it gets to the represention of (a (b . c) d), I find that I cannot understand Shido's answer, which is:
http://www.shido.info/lisp/acl3-1d75.png
What exactly puzzled me is that in his answer d is not followed by nil.
So is his answer right? What is the correct represention of (a (b . c) d) indeed?
lisp common-lisp
asked Dec 31 '18 at 11:16
1MinLeft1MinLeft
336
add a comment |
I am doing the exercises in Paul Graham's ANSI Common Lisp. And I have had a key to the exercises by other person, which is:
http://www.shido.info/lisp/pacl2_e.html
After having finished the exercises for Chapter 3, I refer to that key to check my answers one by one. When it gets to the represention of (a (b . c) d), I find that I cannot understand Shido's answer, which is:
http://www.shido.info/lisp/acl3-1d75.png
What exactly puzzled me is that in his answer d is not followed by nil.
So is his answer right? What is the correct represention of (a (b . c) d) indeed?
lisp common-lisp
asked Dec 31 '18 at 11:16
1MinLeft1MinLeft
336
Shido's answer represents(a (b . c) . d)
– lurker
Jan 8 at 0:32
add a comment |
I am doing the exercises in Paul Graham's ANSI Common Lisp. And I have had a key to the exercises by other person, which is:
http://www.shido.info/lisp/pacl2_e.html
After having finished the exercises for Chapter 3, I refer to that key to check my answers one by one. When it gets to the represention of (a (b . c) d), I find that I cannot understand Shido's answer, which is:
http://www.shido.info/lisp/acl3-1d75.png
What exactly puzzled me is that in his answer d is not followed by nil.
So is his answer right? What is the correct represention of (a (b . c) d) indeed?
lisp common-lisp
asked Dec 31 '18 at 11:16
1MinLeft1MinLeft
336
I am doing the exercises in Paul Graham's ANSI Common Lisp. And I have had a key to the exercises by other person, which is:
http://www.shido.info/lisp/pacl2_e.html
After having finished the exercises for Chapter 3, I refer to that key to check my answers one by one. When it gets to the represention of (a (b . c) d), I find that I cannot understand Shido's answer, which is:
http://www.shido.info/lisp/acl3-1d75.png
What exactly puzzled me is that in his answer d is not followed by nil.
So is his answer right? What is the correct represention of (a (b . c) d) indeed?
lisp common-lisp
lisp common-lisp
asked Dec 31 '18 at 11:16
1MinLeft1MinLeft
336
asked Dec 31 '18 at 11:16
1MinLeft1MinLeft
336
edited Dec 31 '18 at 11:29
1MinLeft
asked Dec 31 '18 at 11:16
1MinLeft1MinLeft
336
asked Dec 31 '18 at 11:16
1MinLeft1MinLeft
336
asked Dec 31 '18 at 11:16
1MinLeft1MinLeft
336
336
Shido's answer represents(a (b . c) . d)
– lurker
Jan 8 at 0:32
add a comment |
Shido's answer represents(a (b . c) . d)
– lurker
Jan 8 at 0:32
Shido's answer represents
(a (b . c) . d)– lurker
Jan 8 at 0:32
Shido's answer represents
(a (b . c) . d)– lurker
Jan 8 at 0:32
add a comment |
2 Answers
2
active
oldest
votes
You can use the sdraw program:
(load "sdraw.generic.lisp")
(sdraw '(a (b . c) d))
[*|*]--->[*|*]------->[*|*]--->NIL
| | |
v v v
A [*|*]--->C D
|
v
B
From this you can see that your idea is correct.
answered Dec 31 '18 at 14:45
RenzoRenzo
17.5k43043
add a comment |
The way to answer questions like this is to get the system to answer them for you. Unfortunately doing this properly requires understanding of how the CL printing system works which is not that simple (in fact: I have forgotten how to do this properly!). But you can write a mindless function which turns things into strings and which uses the object system to turn various sorts of things into strings in a way which is suitable. This isn't going to work for objects which are not conses but which contain conses, but it is quite adequate for simple purposes:
(defgeneric thing->string (thing)
(:method ((thing t))
;; any kind of thing we don't know about gets printed like this
(format nil "~A" thing))
(:method ((thing cons))
;; conses get printed like this
(format nil "(~A . ~A)"
(thing->string (car thing))
(thing->string (cdr thing)))))
Now: (thing->string ...) will answer your question.
answered Dec 31 '18 at 12:33
tfbtfb
2,4021312
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
You can use the sdraw program:
(load "sdraw.generic.lisp")
(sdraw '(a (b . c) d))
[*|*]--->[*|*]------->[*|*]--->NIL
| | |
v v v
A [*|*]--->C D
|
v
B
From this you can see that your idea is correct.
answered Dec 31 '18 at 14:45
RenzoRenzo
17.5k43043
add a comment |
You can use the sdraw program:
(load "sdraw.generic.lisp")
(sdraw '(a (b . c) d))
[*|*]--->[*|*]------->[*|*]--->NIL
| | |
v v v
A [*|*]--->C D
|
v
B
From this you can see that your idea is correct.
answered Dec 31 '18 at 14:45
RenzoRenzo
17.5k43043
add a comment |
You can use the sdraw program:
(load "sdraw.generic.lisp")
(sdraw '(a (b . c) d))
[*|*]--->[*|*]------->[*|*]--->NIL
| | |
v v v
A [*|*]--->C D
|
v
B
From this you can see that your idea is correct.
answered Dec 31 '18 at 14:45
RenzoRenzo
17.5k43043
You can use the sdraw program:
(load "sdraw.generic.lisp")
(sdraw '(a (b . c) d))
[*|*]--->[*|*]------->[*|*]--->NIL
| | |
v v v
A [*|*]--->C D
|
v
B
From this you can see that your idea is correct.
answered Dec 31 '18 at 14:45
RenzoRenzo
17.5k43043
answered Dec 31 '18 at 14:45
RenzoRenzo
17.5k43043
answered Dec 31 '18 at 14:45
RenzoRenzo
17.5k43043
answered Dec 31 '18 at 14:45
RenzoRenzo
17.5k43043
17.5k43043
add a comment |
add a comment |
The way to answer questions like this is to get the system to answer them for you. Unfortunately doing this properly requires understanding of how the CL printing system works which is not that simple (in fact: I have forgotten how to do this properly!). But you can write a mindless function which turns things into strings and which uses the object system to turn various sorts of things into strings in a way which is suitable. This isn't going to work for objects which are not conses but which contain conses, but it is quite adequate for simple purposes:
(defgeneric thing->string (thing)
(:method ((thing t))
;; any kind of thing we don't know about gets printed like this
(format nil "~A" thing))
(:method ((thing cons))
;; conses get printed like this
(format nil "(~A . ~A)"
(thing->string (car thing))
(thing->string (cdr thing)))))
Now: (thing->string ...) will answer your question.
answered Dec 31 '18 at 12:33
tfbtfb
2,4021312
add a comment |
The way to answer questions like this is to get the system to answer them for you. Unfortunately doing this properly requires understanding of how the CL printing system works which is not that simple (in fact: I have forgotten how to do this properly!). But you can write a mindless function which turns things into strings and which uses the object system to turn various sorts of things into strings in a way which is suitable. This isn't going to work for objects which are not conses but which contain conses, but it is quite adequate for simple purposes:
(defgeneric thing->string (thing)
(:method ((thing t))
;; any kind of thing we don't know about gets printed like this
(format nil "~A" thing))
(:method ((thing cons))
;; conses get printed like this
(format nil "(~A . ~A)"
(thing->string (car thing))
(thing->string (cdr thing)))))
Now: (thing->string ...) will answer your question.
answered Dec 31 '18 at 12:33
tfbtfb
2,4021312
add a comment |
The way to answer questions like this is to get the system to answer them for you. Unfortunately doing this properly requires understanding of how the CL printing system works which is not that simple (in fact: I have forgotten how to do this properly!). But you can write a mindless function which turns things into strings and which uses the object system to turn various sorts of things into strings in a way which is suitable. This isn't going to work for objects which are not conses but which contain conses, but it is quite adequate for simple purposes:
(defgeneric thing->string (thing)
(:method ((thing t))
;; any kind of thing we don't know about gets printed like this
(format nil "~A" thing))
(:method ((thing cons))
;; conses get printed like this
(format nil "(~A . ~A)"
(thing->string (car thing))
(thing->string (cdr thing)))))
Now: (thing->string ...) will answer your question.
answered Dec 31 '18 at 12:33
tfbtfb
2,4021312
The way to answer questions like this is to get the system to answer them for you. Unfortunately doing this properly requires understanding of how the CL printing system works which is not that simple (in fact: I have forgotten how to do this properly!). But you can write a mindless function which turns things into strings and which uses the object system to turn various sorts of things into strings in a way which is suitable. This isn't going to work for objects which are not conses but which contain conses, but it is quite adequate for simple purposes:
(defgeneric thing->string (thing)
(:method ((thing t))
;; any kind of thing we don't know about gets printed like this
(format nil "~A" thing))
(:method ((thing cons))
;; conses get printed like this
(format nil "(~A . ~A)"
(thing->string (car thing))
(thing->string (cdr thing)))))
Now: (thing->string ...) will answer your question.
answered Dec 31 '18 at 12:33
tfbtfb
2,4021312
answered Dec 31 '18 at 12:33
tfbtfb
2,4021312
answered Dec 31 '18 at 12:33
tfbtfb
2,4021312
answered Dec 31 '18 at 12:33
tfbtfb
2,4021312
2,4021312
add a comment |
add a comment |
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Shido's answer represents
(a (b . c) . d)– lurker
Jan 8 at 0:32