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From: "Pascal J. Bourguignon" <p...@informatimago.com>
Newsgroups: comp.lang.lisp
Subject: Re: accumulate function in Lisp
Date: Sun, 06 Mar 2011 15:36:12 +0100
Organization: Informatimago
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Rainer Joswig <jos...@lisp.de> writes:

> On 6 Mrz., 14:24, "WJ" <w_a_x_...@yahoo.com> wrote:
>> Frank Buss wrote:
>> > Krishna Myneni wrote:
>>
>> > > Apologies in advance if this is a naive question, since I'm new to
>> > > Lisp (my background is Forth).
>>
>> > > Is there an intrinsic function in Common Lisp which will iterate over
>> > > each element of the list and apply a binary function between an
>> > > integer and the list element. The return value should be an integer.
>> > > I'm familiar with "mapcar", "every", and "some", but I can't see how
>> > > to adapt them to this problem. I realize one can write such a list
>> > > iterator, but my question is whether or not such a function already
>> > > exists, or, if not, whether there is a commonly accepted name for such
>> > > an iterator. Thanks.
>>
>> > Yes, reduce:
>>
>> > CL-USER 1 > (reduce #'+ '(1 2 3) :initial-value 10)
>> > 16
>>
>> > CL-USER 2 >
>>
>> Scheme:
>>
>> guile> (fold + 10 '(1 2 3))
>> 16
>
> CL-USER 28 > (reduce '+ (cons 10 '(1 2 3)))
> 16

          (f '+ 10 '(1 2 3))

Even shorter than guile...

with:  (defun f (f i s) (reduce f s :initial-value i)) 

Notice that contrarily to scheme, or Rainer's solution, f works on
vectors too:

         (f '+ 10 (vector 1 2 3))

-- 
__Pascal Bourguignon__                     http://www.informatimago.com/
A bad day in () is better than a good day in {}.