Path: csiph.com!usenet.pasdenom.info!weretis.net!feeder4.news.weretis.net!nuzba.szn.dk!pnx.dk!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail
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: Fri, 02 Nov 2012 14:45:19 +0100
Organization: Informatimago
Lines: 36
Message-ID: <87pq3wqftc.fsf@voyager.informatimago.com>
References: <8120f97b-15c2-4ce8-827a-158e955fb73f@z2g2000yqj.googlegroups.com> <9972e570-2504-4401-8de8-49eb1929fdfd@c17g2000yqe.googlegroups.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
X-Trace: individual.net Qz5czpSTSZq0Q9O3MTJN0ArBgukAke/upEaREAunaTcWrIIriRUAhKDVGUtK+wWUmK
Cancel-Lock: sha1:MmRkMjQ1ZjRlNGY0ZTE5OWMzMTk2NzhlN2QzOTA2Y2Q3NzYyYWE1Yg== sha1:Z1DnXatAhd32P7KXhY636D2E4SY=
Face: iVBORw0KGgoAAAANSUhEUgAAADAAAAAwAQMAAABtzGvEAAAABlBMVEUAAAD///+l2Z/dAAAA oElEQVR4nK3OsRHCMAwF0O8YQufUNIQRGIAja9CxSA55AxZgFO4coMgYrEDDQZWPIlNAjwq9 033pbOBPtbXuB6PKNBn5gZkhGa86Z4x2wE67O+06WxGD/HCOGR0deY3f9Ijwwt7rNGNf6Oac l/GuZTF1wFGKiYYHKSFAkjIo1b6sCYS1sVmFhhhahKQssRjRT90ITWUk6vvK3RsPGs+M1RuR mV+hO/VvFAAAAABJRU5ErkJggg==
X-Accept-Language: fr, es, en
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.2 (gnu/linux)
Xref: csiph.com comp.lang.functional:439 comp.lang.lisp:11880 comp.lang.scheme:1118 comp.programming:2439 comp.emacs:1607

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__