Nicolas Alvarez <nic### [at] gmailcom> wrote:
> Warp wrote:
> > Invisible <voi### [at] devnull> wrote:
> >> Now what happens if you want to only process elements having some
> >> arbitrary property? (E.g., only the odd numbers.)
> > 
> > I make the function take a functor which tells which elements to
> > process.
> > This is a standard technique in C++.

> You can even write a custom iterator that, when incremented, skips even
> numbers. Then you can use it with the existing fold function.

  Good point. In fact, you can create iterators which do a lot of fancy
things, like for example one which traverses the container backwards
(a standard such iterator exists), if you need to perform an operation
in reverse order, or whatever you wish. And all this without having to
modify nor copy the data container.

  Well, I assume that when you say in Haskell "reverse the list and then
give it to this function" the compiler might be able to avoid copying the
list to another one with the elements in reverse order.

-- 
                                                          - Warp

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