Topic: (discussion) Costruct procedures with Lambda

[JohnK]

What do you think of using lambda in your procedures instead of separate named procedures. Example:

Code: [Select]

(defun square (x) (* x x) )

(defun sum-of-two-squares (x y)
  (+ (square x) (square y) )
 )
or even:

Code: [Select]

(defun sum-of-two-squares ( x y / sqaure )
 
    (defun square (x) (* x x) )

  (+ (square x) (square y) )
 )
v.s.

Code: [Select]

(defun sum-of-two-squares-redo (x y)
  ( (lambda (x y)
      (+ x y ))
   (* x x)
   (* y y)
   )
 )

My thoughts:
Pros:
o  I like the idea of no named procedures floating about even if they could be wrapped up. Makes the procedure seem cleaner.
o  Almost seems a bit more "readable"--More like it "shoud" be...kinda. Although the overall code looks/feels diff then either of the two above there arent any seperate named procedures floating about in the code when it comes time to maintain this procedure.

Cons:
o  Makes you think a bit more a head of time then the other two. (Which isnt that bad)
o  Its almost less readable upon first glance.

I'll think about this some more, but i wanted to get your thoughts on the subject.

[Keith™]

I have used lambda on various occasions when writing a standout function was not warranted, but I must say that if the procedure is something that can be used elsewhere, it is almost (note I said almost) always a good idea to globalize it within the code and utilize it as needed rather than rewrite sections of code.

In your above example, I would have not used lambda, but then I like to make things a bit more compact.

Code: [Select]

(defun sum-of-two-squares ( x y )
 (+ (* X X)(* Y Y))
)


[JohnK]

Well neither would i--in the example above--but i needed an example. *lol*

[Keith™]

I figured as much, but I felt compelled ... now why do I do that ...

[JohnK]

Hi kpblc, Welcome to theSwamp.

I looked at the link--I know its in, what looks to me like Russian, but i looked at all the code--I dont see what your trying to convey. Can you try to explain it to me again. (Im not understanding.)

[kpblc]

Ooohhh, sorry! I'm terrible sorry!
I'd like to show lambda-functions code, but the code was the recursion example!
> Moderators : Please, erase my posts in this topic...
Anyway, author send me this code for getting summ of squares:

Code: [Select]

(defun sum-squares-lst (lst)
  (if lst
    (+ (* (car lst) (car lst)) (sum-squares-lst (cdr lst)))
    0
  ) ;_  if
) ;_  defun
;;(sum-squares-lst '(2 3)); => 13
;;(sum-squares-lst '(2 3 4)); => 29
;;(sum-squares-lst '(1 2 3 4 5 6 7 8 9 10)); => 385

[JohnK]

Oh no need to be sorry.

Im a moderator I can delete your post if you wish.

[kpblc]

Yes, I think it's good idea to delete my first post "Posted on: Today at 09:14:35 AM" - it's out of theme.
Thank you.

[JohnK]

You got it.

[Keith™]

Might it be a good idea to simply clean up the post and leave the link to the other site for other users wishing to see what might be available there?

[JohnK]

Ok, I removed the post. (I have it saved in a file on my computer if you wish to have it.)

[JohnK]

Might it be a good idea to simply clean up the post and leave the link to the other site for other users wishing to see what might be available there?

To late. *lol* Good idea.
I saved the link. Here it is: [ http://dwg.ru/forum/viewtopic.php?t=6571&start=15) ]

[MP]

Generally speaking, putting aside the use of lambda in mapcar or apply calls, I use lambda where --

• I need a function but not a formal declaration.
• [to me] it improves the clarity or intent of my code.
• where I envision a code cluster may later become a formally declared function.
• I wish to exploit the fact I can localize variables -- declaring and using them right where I need 'em.

I personally wouldn't use it the way you demonstrated as it seemed to obfuscate things a bit without adding any tangible benefit that I could see, though that gets into the whole "style" thing where things can be rather subjective.

It's a very interesting topic John. I apologise, but I can't contribute more than the above (like examples) at this time. If you search the swamp using "mp" and "lambda" you may find some examples of my use, good and bad no doubt.

[JohnK]

MP, So more in a traditional mapcar-lambda type of situation?
...Do you have a small example lying arround you can post? (Dosent have to be anything fancy just what ever you got infront of you.)

[JohnK]

Oh ok.(I just saw the edit you added.) Im on it.