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

[Robert L.]

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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