Topic: RemoveNth ...

[MP]

Having residual caffiene in my system and thinking about Chuck's discussion earlier today on car | cdr I got to thinking about a real old vanilla lisp version of removenth that I had penned using cdr, member etc. and then dreamed up this little number I thought might make Se7en's forehead twitch a bit.

Code: [Select]

(defun RemoveNth ( n lst / len foo i )

    (defun foo (x)
        (if (eq n (setq i (1+ i)))
            (defun foo (x) nil)
        )  
    )

    (cond
        (   (zerop n) (cdr lst))
        (   (eq n (1- (setq len (length lst))))
            (reverse (cdr (reverse lst)))
        )
        (   (< (setq i -1) n len)
            (vl-remove-if 'foo lst)
        )  
        (   lst  )
    )
   
)

;;  examples of use
 
(setq lst '(0 1 2 3 4 5 6 7))
 
(removenth -1 lst) ;; => (0 1 2 3 4 5 6 7)
 
(removenth 0 lst)  ;; => (1 2 3 4 5 6 7)
 
(removenth 4 lst)  ;; => (0 1 2 3 5 6 7)
 
(removenth 7 lst)  ;; => (0 1 2 3 4 5 6)
 
(removenth 8 lst)  ;; => (0 1 2 3 4 5 6 7)
What do ya think?



(Pssst -- there's room for optimization, can ya see it?)

Edit: Updated to reflect this post, much better.

[Kerry]

heh, I'm pleased It doesn't have comments in it

That double defun is tricky

[MP]

[Mark]

hehehehe ........ LOL

that's great stuff MP.

[MP]

Too much coffee today; seriously.

Thank you Kerry, thank you Mark.

[Kerry]

hehehe .. is that the code monkey ??


is he caffinated too ?

[MP]

He's known as <PeterSellersVoice>'the code minkey'</PeterSellersVoice>.

[Kerry]

That is a sick bit of code Michael. What brand of coffee do you have in the drip bag.?

[MP]

Instant. Works fast -- no waiting.

[nivuahc]

<-- sockless

[MP]

Do you guys like this variant?

Code: [Select]

(defun RemoveNth ( n lst / len foo i )

    (defun foo (pair)
        (if (eq n (setq i (1+ i)))
            (defun foo (pair) nil)
        )  
    )

    (cond
        (   (zerop n) (cdr lst))
        (   (eq n (1- (setq len (length lst))))
            (reverse (cdr (reverse lst)))
        )
        (   (< (setq i -1) n len)
            (vl-remove-if 'foo lst)
        )  
        (   lst  )
    )
   
)

[nivuahc]

Now you're just being a show-off

:dood:

[MP]

Actually, it should read like this --

Code: [Select]

(defun RemoveNth ( n lst / len foo i )

    (defun foo (x)
        (if (eq n (setq i (1+ i)))
            (defun foo (x) nil)
        )  
    )

    (cond
        (   (zerop n) (cdr lst))
        (   (eq n (1- (setq len (length lst))))
            (reverse (cdr (reverse lst)))
        )
        (   (< (setq i -1) n len)
            (vl-remove-if 'foo lst)
        )  
        (   lst  )
    )
   
)
There is still at least one level of optimization that can be done in my mind. Any takers?

[Mark]

Any takers?

yea right ..... I wish.

I'm still hung-up on ...

Code: [Select]

(defun foo (x)
        (if (eq n (setq i (1+ i)))
            (defun foo (x) nil)
        )

[MP]

Want for me to 'splain?

BRB (grabbin' a mug o' brew ...)