[Haskell-cafe] Church vs Boehm-Berarducci encoding of Lists

[Ivan Lazar Miljenovic]

On 18 September 2012 18:27,  <oleg at okmij.org> wrote:
>
> There has been a recent discussion of ``Church encoding'' of lists and
> the comparison with Scott encoding.
>
> I'd like to point out that what is often called Church encoding is
> actually Boehm-Berarducci encoding. That is, often seen
>
>> newtype ChurchList a =
>>     CL { cataCL :: forall r. (a -> r -> r) -> r -> r }
>
> (in http://community.haskell.org/%7Ewren/list-extras/Data/List/Church.hs )
>
> is _not_ Church encoding. First of all, Church encoding is not typed
> and it is not tight. The following article explains the other
> difference between the encodings
>
>         http://okmij.org/ftp/tagless-final/course/Boehm-Berarducci.html
>
> Boehm-Berarducci encoding is very insightful and influential. The
> authors truly deserve credit.
>
> P.S. It is actually possible to write zip function using Boehm-Berarducci
> encoding:
>         http://okmij.org/ftp/ftp/Algorithms.html#zip-folds

You have one too many "ftp/" in there (in case others get confused
about why the link fails).

>
>
>
>
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-- 
Ivan Lazar Miljenovic
Ivan.Miljenovic at gmail.com
http://IvanMiljenovic.wordpress.com