Prev: the Modernization of Emacs
Next: Clipboard Access on Windows
From: Jonathan Heusser on 19 Jun 2006 04:12
Emre Sevinc wrote:
> Jonathan Heusser <jonny(a)drugphish.ch> writes:
>
>>> CL-USER> [x (x <- '(1 2 3)) (oddp x)]
>>> (1 3)
>>>
>> CL-USER> (loop for x in (list 1 2 3) when (oddp x) collect x)
>> (1 3)
>
> Certainly it does. However I'd still be happy to have alternatives
> and "more natural" (whatever that means, at least it rings some
> bells for me ;-)) syntax as well as a more compact and concise one.
>
all a matter of taste which version is more natural/readable, right ;)
From: Frank Buss on 19 Jun 2006 04:38
joswig(a)corporate-world.lisp.de wrote:

> For combinations of this kind of stuff I really prefer the functional
> approach:
> CL-USER 5 > (remove-if-not 'oddp '(1 2 3))
> (1 3)

I know it is possible, but I'm not sure aboout how to write the following
with a functional approach:

> (loop for i from 1 to 10 collect (loop for j from 1 to i collect j))
((1) (1 2) (1 2 3) (1 2 3 4) (1 2 3 4 5) (1 2 3 4 5 6) (1 2 3 4 5 6 7) (1 2
3 4 5 6 7 8) (1 2 3 4 5 6 7 8 9) (1 2 3 4 5 6 7 8 9 10))

--
Frank Buss, fb(a)frank-buss.de
http://www.frank-buss.de, http://www.it4-systems.de
From: Pascal Costanza on 19 Jun 2006 05:38
Marc Battyani wrote:
> "Emre Sevinc" <emres(a)bilgi.edu.tr> wrote
>>> LOOP does some kind of list comprehension aswell, without an additional
>>> software.
>> Certainly it does. However I'd still be happy to have alternatives
>> and "more natural" (whatever that means, at least it rings some
>> bells for me ;-)) syntax as well as a more compact and concise one.
>>
>> LOOP construct of CL has a very nice English-like syntax
>> but the one presented in the paper I mentioned in my original post
>> also provides a good syntax for the mathematically inclined.
>
> Here are other list comprehension librairies:
> http://www.cl-user.net/asp/search?search=comprehension

See also http://p-cos.net/lisp-ecoop/submissions/Nystrom.pdf


Pascal

--
3rd European Lisp Workshop
July 3 - Nantes, France - co-located with ECOOP 2006
http://lisp-ecoop06.bknr.net/
From: Marcin 'Qrczak' Kowalczyk on 19 Jun 2006 18:32
Frank Buss <fb(a)frank-buss.de> writes:

> I know it is possible, but I'm not sure aboout how to write the following
> with a functional approach:
>
>> (loop for i from 1 to 10 collect (loop for j from 1 to i collect j))
> ((1) (1 2) (1 2 3) (1 2 3 4) (1 2 3 4 5) (1 2 3 4 5 6) (1 2 3 4 5 6 7) (1 2
> 3 4 5 6 7 8) (1 2 3 4 5 6 7 8 9) (1 2 3 4 5 6 7 8 9 10))

It's a matter of appropriate building blocks. For example:
- an arithmetic sequence (range)
- map
- conversion of a sequence to a list

--
__("< Marcin Kowalczyk
\__/ qrczak(a)knm.org.pl
^^ http://qrnik.knm.org.pl/~qrczak/
From: Alexander Schmolck on 19 Jun 2006 19:50
Frank Buss <fb(a)frank-buss.de> writes:

> joswig(a)corporate-world.lisp.de wrote:
>
> > For combinations of this kind of stuff I really prefer the functional
> > approach:
> > CL-USER 5 > (remove-if-not 'oddp '(1 2 3))
> > (1 3)
>
> I know it is possible, but I'm not sure aboout how to write the following
> with a functional approach:
>
> > (loop for i from 1 to 10 collect (loop for j from 1 to i collect j))
> ((1) (1 2) (1 2 3) (1 2 3 4) (1 2 3 4 5) (1 2 3 4 5 6) (1 2 3 4 5 6 7) (1 2
> 3 4 5 6 7 8) (1 2 3 4 5 6 7 8 9) (1 2 3 4 5 6 7 8 9 10))


e.g. (mapcar #'upto (upto 10)) or (unfold (its = 10) #'upto #'1+ 1)

with (untested)

(defun upto (n) (labels ((rec (i) (and (plusp i) (cons (- n i -1) (rec (- i 1)))))) (rec n)))
(defun unfold (p f g seed)
(and (not (funcall p seed))
(cons (funcall f seed)
(unfold p f g (funcall g seed)))))
(defmacro its (f &rest rest) `(lambda (#1=#:x) (,f #1# ,@rest)))

'as
First  |  Prev  |  Next  |  Last
Pages: 1 2 3
Prev: the Modernization of Emacs
Next: Clipboard Access on Windows