Topic: [challenge] A27 : delete-if / delete-if-not

[JohnK]

@pBe
I just noticed your latest edit now. Your latest edit code looks good (looks to meet the specifications).

[pBe]

@pBe
I just noticed your latest edit now. Your latest edit code looks good (looks to meet the specifications).

Thank you for that @JohnK, it did not make the cut but at least it meets the specifications
I will read it thoroughly next time.

[dexus]

Hi,
To avoid calling apply (or eval) at each loop, it would be more efficient to set f to (eval f) before the loops and simply call (f item) at each loop.

Code - Auto/Visual Lisp: [Select]

1. (defun deleteif (f l / loop)
2.   (defun loop (f l)
3.     (cond
4.       ((not l) l)
5.       ((f (car l)) (deleteif f (cdr l)))
6.       ((cons (car l) (deleteif f (cdr l))))
7.     )
8.   )
9.   (loop (eval f) l)
10. )

Wait, shouldn't be the loop function that does the recursion instead of the deleteif? This way it still does an eval every loop.

If you create a new function anyway, you don't even have to pass it along as a variable.
Just create the variable in the parent function and use that, I'm not sure if that is more efficient though.

Code - Auto/Visual Lisp: [Select]

1. (defun deleteif (f l / loop)
2.   (setq f (eval f))
3.   (defun loop (l)
4.     (cond
5.       ((not l) l)
6.       ((f (car l)) (loop (cdr l)))
7.       ((cons (car l) (loop (cdr l))))
8.     )
9.   )
10.   (loop l)
11. )