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.Re: YANQ - When to map, when to iterate, when to recurse? And why CLOS?

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  .Re: YANQ - When to map, when to iterate, when to recurse? And why CLOS? "Robert L." <No_spamming@noWhere_7073.org> - 2017-01-21 07:52 +0000

#54218 — .Re: YANQ - When to map, when to iterate, when to recurse? And why CLOS?

Wade Humeniuk wrote:

> John Connors wrote: 
> 
> > Yet Another Noob Question. 
> 
> > What are the characteristics of each implementation? 
> 
> > How can I tell which I should be writing in what context... 
> 
> > (defun find-indicies (lst tst) 
> >   (let ((li 0)) 
> >     (labels ((qpred (a) 
> >                (incf li) 
> >                (if (funcall tst a) 
> >                    (1- li) 
> >                    nil))) 
> >       (remove nil (mapcar #'qpred lst))))) 
> 
> > (defun find-indices (lst tst) 
> >   (loop 
> >    for el in lst 
> >    counting t into index 
> >    if (funcall tst el) 
> >    collect index)) 
> 
> You are allergic to loop 
> 
> (defun find-indices (list test) 
>    (loop for element in list 
>          for index from 1 
>          when (funcall test element) collect index))

Ruby:

def find_indices array
  array.each_with_index.grep(->((n,i)){yield n}, &:last)
end

find_indices(%w(a bb c d e ff)){|s| s.size > 1}
    ==>[1, 5]

In Forth?


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Ruth Bader Ginsburg, Elana Kagan, and Stephen Breyer.
www.jta.org/2016/03/16/news-opinion/united-states/obama-to-name-jewish-federal-judge-to-supreme-court

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