TheSwamp

Code Red => AutoLISP (Vanilla / Visual) => Topic started by: Jeremy Dunn on May 19, 2019, 04:14:04 PM

Title: How to determine equality of nesting
Post by: Jeremy Dunn on May 19, 2019, 04:14:04 PM

Let us say I want to determine if two expressions have the same form or not. I will call the function form= to write examples. Here are some examples to illustrate

(form= 3 (a b)) -> nil
(form= (a (b c)) (a b c)) -> nil
(form= (1 (2 3)) (5 (6 7))) -> T

So the idea is that expressions can be equal even if the individual elements are not and that only the number of elements and the nesting of the elements are important. Anyone have a function that can do this?

Title: Re: How to determine equality of nesting
Post by: gile on May 19, 2019, 05:24:37 PM

Hi,

If the order of items matters
(foo '(1 (2 3)) '(5 (6 7))) return T
(foo '(1 (2 3)) '((6 7) 5)) return nil

Code - Auto/Visual Lisp: [Select]

1. (defun foo (a b)
2.   (or
3.     (and (atom a) (atom b))
4.     (and (listp a)
5.          (listp b)
6.          (= (length a) (length b))
7.          (vl-every 'foo a b)
8.     )
9.   )
10. )

If the order does not matter
(bar '(1 (2 3) (b)) '(5 (6 7) (9))) returns T
(bar '(1 (2 3) (b)) '(5 (9) (6 7))) returns T

Code - Auto/Visual Lisp: [Select]

1. (defun bar (a b)
2.   (or
3.     (and (atom a) (atom b))
4.     (and (listp a)
5.          (listp b)
6.          (= (length a) (length b))
7.          (vl-every 'bar
8.                    (vl-sort (vl-remove-if 'atom a) '(lambda (x y) (< (length x) (length y))))
9.                    (vl-sort (vl-remove-if 'atom b) '(lambda (x y) (< (length x) (length y))))
10.          )
11.     )
12.   )
13. )

Title: Re: How to determine equality of nesting
Post by: myloveflyer on May 23, 2019, 11:26:59 PM

Quote from: gile on May 19, 2019, 05:24:37 PM

Hi,

If the order of items matters
(foo '(1 (2 3)) '(5 (6 7))) return T
(foo '(1 (2 3)) '((6 7) 5)) return nil

Code - Auto/Visual Lisp: [Select]

1. (defun foo (a b)
2.   (or
3.     (and (atom a) (atom b))
4.     (and (listp a)
5.          (listp b)
6.          (= (length a) (length b))
7.          (vl-every 'foo a b)
8.     )
9.   )
10. )

If the order does not matter
(bar '(1 (2 3) (b)) '(5 (6 7) (9))) returns T
(bar '(1 (2 3) (b)) '(5 (9) (6 7))) returns T

Code - Auto/Visual Lisp: [Select]

1. (defun bar (a b)
2.   (or
3.     (and (atom a) (atom b))
4.     (and (listp a)
5.          (listp b)
6.          (= (length a) (length b))
7.          (vl-every 'bar
8.                    (vl-sort (vl-remove-if 'atom a) '(lambda (x y) (< (length x) (length y))))
9.                    (vl-sort (vl-remove-if 'atom b) '(lambda (x y) (< (length x) (length y))))
10.          )
11.     )
12.   )
13. )

Gile,Nice Work!

Title: Re: How to determine equality of nesting
Post by: Lee Mac on May 25, 2019, 12:06:40 PM

Nice code gile  :-)

Here's an alternative to allow for dotted pairs -

Code - Auto/Visual Lisp: [Select]

1. (defun foo ( a b )
2.     (or (and (atom  a) (atom  b))
3.         (and (listp a) (listp b)
4.              (= (vl-list-length a) (vl-list-length b))
5.              (foo (car a) (car b))
6.              (foo (cdr a) (cdr b))
7.         )
8.     )
9. )

Code - Auto/Visual Lisp: [Select]

1. _$ (foo 1 1)
2. T
3. _$ (foo 1 '(1))
4. nil
5. _$ (foo 1 '(1 . 1))
6. nil
7. _$ (foo '(1) '(1))
8. T
9. _$ (foo '(1) '(1 . 1))
10. nil
11. _$ (foo '(1 . 1) '(1 . 1))
12. T

Title: Re: How to determine equality of nesting
Post by: bruno_vdh on June 14, 2019, 04:40:01 AM

Hello,
Maybe I do not understand the subject, but why?

Quote

_$ (foo '(1) '(1 . 1))
nil

If we consider this:

Code: [Select]

_$ (car '(1.1))
1.1
_$ (car '(1))
1
_$ (cdr '(1.1))
nil
_$ (cdr '(1))
nil

So this definition seems to me preferable ...

Code: [Select]

(defun f (a b)
  (cond
    ((atom a) (atom b))
    ((atom b) nil)
    ((f (car a) (car b)) (f (cdr a) (cdr b)))
  )
)


Code: [Select]

_$ (f 1 1)
T
$ (f 1 '(1))
nil
_$ (f 1 '(1 . 1))
nil
_$ (f '(1) '(1 . 1))
T
_$ (f '(1 . 1) '(1 . 1))
T


Title: Re: How to determine equality of nesting
Post by: Lee Mac on June 14, 2019, 08:10:08 AM

Quote from: bruno_vdh on June 14, 2019, 04:40:01 AM

Quote

_$ (foo '(1) '(1 . 1))
nil

If we consider this:

Code: [Select]

_$ (car '(1.1))
1.1
_$ (car '(1))
1
_$ (cdr '(1.1))
nil
_$ (cdr '(1))
nil


'(1 . 1) is very different to '(1.1) - the former represents a dotted pair, the latter a list containing a single item.

As such, the comparison would become:

Code - Auto/Visual Lisp: [Select]

1. _$ (car '(1 . 1))
2. 1
3. _$ (car '(1))
4. 1
5. _$ (cdr '(1 . 1))
6. 1
7. _$ (cdr '(1))
8. nil

Title: Re: How to determine equality of nesting
Post by: bruno_vdh on June 14, 2019, 12:07:26 PM

Yes I was too fast in my conclusions, thanks for correcting my mistake