Lis(t|p) comprehensions
in [Lisp]
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From: Emre Sevinc on 19 Jun 2006 02:21 I was browsing around lazily when I came across the List comprehensions article in Wikipedia: http://en.wikipedia.org/wiki/List_comprehensions I looked at the first few lines and I sighed "oh how close-to-natural in terms of mathematical notation! But it looks like Haskell, how would it be in Common Lisp?" After showing this to one of my fellow Turkish Lispers, HB, he told me that he had just found a paper by Guy Lapalme [1], written in 1991 with a title of "Implementation of a Lisp comprehension macro": http://rali.iro.umontreal.ca/Publications/urls/LapalmeLispComp.pdf We both rushed to our Emacsen + SLIMEs, typed the code: http://paste.lisp.org/display/21380 and then saw that we were able to write similar list comprehension code like that: CL-USER> [x (x <- '(1 2 3)) (oddp x)] (1 3) CL-USER> [(list x y) (x <- '(a b c)) (y <- '(1 2 3))] ((A 1) (A 2) (A 3) (B 1) (B 2) (B 3) (C 1) (C 2) (C 3)) (The paper also included the classical QuickSort implementation that used this list comprehension notation). Once again I understood why Lisp is called a "programmable programming language." In the conclusion, author mentions advantages and drawbacks of the implementation of this notation, he also compares it to the Series. Since the article was written about 15 years ago, I just wondered if this macro became a part of a frequently used package. Maybe Lispers who know much more will tell us more about this subject? 1- http://www.iro.umontreal.ca/~lapalme/ -- Emre Sevinc eMBA Software Developer Actively engaged in: http://emba.bilgi.edu.tr http://ileriseviye.org http://www.bilgi.edu.tr http://fazlamesai.net Cognitive Science Student http://cazci.com http://www.cogsci.boun.edu.tr
From: Jonathan Heusser on 19 Jun 2006 02:58 > > 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) LOOP does some kind of list comprehension aswell, without an additional software.
From: Emre Sevinc on 19 Jun 2006 03:45 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) > > 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. Happy hacking, -- Emre Sevinc eMBA Software Developer Actively engaged in: http://emba.www.bilgi.edu.tr http://ileriseviye.org http://www.bilgi.edu.tr http://fazlamesai.net Cognitive Science Student http://cazci.com http://www.cogsci.boun.edu.tr
From: Marc Battyani on 19 Jun 2006 03:54 "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 Marc
From: joswig on 19 Jun 2006 04:11
Jonathan Heusser schrieb: > > > > 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) > > LOOP does some kind of list comprehension aswell, without an additional > software. 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) |