newlispfanclub.alh.net

Posted: **Fri Aug 30, 2013 7:12 pm**

Is it possible to have to have reducers in newlisp too as mentioned in this http://adambard.com/blog/Reducers-expla ... gh-Python/ ?

The key takeaway from the article is

This is the idea behind reducers. If you take your mapping function (map, filter, flatten, etc.), and have it modify the reducing function, you can perform any number and combination of mappings without having to repeatedly iterate through the list.

Posted: **Sat Aug 31, 2013 5:40 am**

Thanks, that is a very cool URL.

I sure could have used Reducers when I implemented the (combinations) function.

To make it efficient, I had to switch from map to dolist to avoid that exact problem that the Reducer functions address.

http://www.newlisp.org/index.cgi?page=Code_Snippets

Code: Select all

   (define (combinations n k (r '()))
     (if (= (length r) n)
       (list (sort r <))
       (apply append (map 
                (fn (x) (combinations n ((+ 1 $idx) k) (cons x r))) k))))

 ; (combinations 2 '(a b c))
 ; =>  ((a b) (a c) (b c))

I'd really like to know how that would look using Reducers instead of dolist. dolist did do the job very efficiently, map blew up my computer.

newlispfanclub.alh.net

Reducers in newlisp?

Reducers in newlisp?

Re: Reducers in newlisp?