Re: Associativity paradox in functional expressions

From	"Pascal J. Bourguignon" <pjb@informatimago.com>
Newsgroups	comp.lang.functional, comp.lang.lisp, comp.lang.scheme, comp.programming, comp.emacs
Subject	Re: Associativity paradox in functional expressions
Date	2012-11-02 14:45 +0100
Organization	Informatimago
Message-ID	<87pq3wqftc.fsf@voyager.informatimago.com> (permalink)
References	<8120f97b-15c2-4ce8-827a-158e955fb73f@z2g2000yqj.googlegroups.com> <9972e570-2504-4401-8de8-49eb1929fdfd@c17g2000yqe.googlegroups.com>

Cross-posted to 5 groups.

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Totaram Sanadhya <swami.totaram.sanadhya@gmail.com> writes:

> Hi,
>
> My main functional language is emacs based lisp.
>
> I am not exactly clear about the associativity.
>
> On the one hand the elements of a list such as (a b c d) are right
> associative
>
> (cons 'a (cons 'b (cons 'c (cons 'd nil))))    C-x C-e
>
> ==> (a b c d)
>
> On the other hand a curried function such as (f x y z) is left
> associative by definition
>
> (...(f x) y) z)
>
> How do you resolve this paradox?

By defining a leflt-associative function.

    (defun lons (prefix item)
       (append prefix (list item)))

    (lons (lons (lons (lons nil 'a) 'b) 'c) 'd)
    --> (a b c d)

    (lons (lons (lons '(f) 'x) 'y) 'z)
    --> (f x y z)


-- 
__Pascal Bourguignon__

Thread

Re: Associativity paradox in functional expressions Totaram Sanadhya <swami.totaram.sanadhya@gmail.com> - 2012-10-31 00:24 -0700
  Re: Associativity paradox in functional expressions Barb Knox <see@sig.below> - 2012-10-31 21:14 +1300
    Re: Associativity paradox in functional expressions Totaram Sanadhya <swami.totaram.sanadhya@gmail.com> - 2012-10-31 10:34 -0700
      Re: Associativity paradox in functional expressions Dirk Thierbach <dthierbach@usenet.arcornews.de> - 2012-10-31 23:36 +0100
  Re: Associativity paradox in functional expressions Nils M Holm <news2009@t3x.org> - 2012-10-31 09:21 +0000
  Re: Associativity paradox in functional expressions "Pascal J. Bourguignon" <pjb@informatimago.com> - 2012-11-02 14:45 +0100
    Re: Associativity paradox in functional expressions Rivka Miller <rivkaumiller@gmail.com> - 2012-11-02 18:59 -0700
      Re: Associativity paradox in functional expressions "Pascal J. Bourguignon" <pjb@informatimago.com> - 2012-11-03 04:14 +0100
        Re: Associativity paradox in functional expressions Rivka Miller <rivkaumiller@gmail.com> - 2012-11-05 16:53 -0800
          Re: Associativity paradox in functional expressions "Pascal J. Bourguignon" <pjb@informatimago.com> - 2012-11-06 07:28 +0100
            Re: Associativity paradox in functional expressions Barb Knox <see@sig.below> - 2012-11-08 17:35 +1300
              Re: Associativity paradox in functional expressions Aatu Koskensilta <aatu.koskensilta@uta.fi> - 2012-11-08 07:42 +0200
                Re: Associativity paradox in functional expressions "Pascal J. Bourguignon" <pjb@informatimago.com> - 2012-11-08 21:47 +0100
                Re: Associativity paradox in functional expressions Barb Knox <see@sig.below> - 2012-11-10 15:13 +1300

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