Re: What is this function called?
On Thu, Jan 1, 2009 at 10:14 PM, Andrew Baine andrew.ba...@gmail.com wrote: I want to get a seq of successive rests of the given seq: user (defn f [seq] (if (empty? seq) nil (lazy-cons seq (f (rest seq) #'user/f user (f '(1 2 3 4)) ((1 2 3 4) (2 3 4) (3 4) (4)) That's very similar to tails in Haskell: http://www.zvon.org/other/haskell/Outputlist/tails_f.html user (take 10 (map #(take 5 %) (f (iterate inc 1 ((1 2 3 4 5) (2 3 4 5 6) (3 4 5 6 7) (4 5 6 7 8) (5 6 7 8 9) (6 7 8 9 10) (7 8 9 10 11) (8 9 10 11 12) (9 10 11 12 13) (10 11 12 13 14)) For this particular example, you could use 'partition': (take 10 (partition 5 1 (iterate inc 1))) Does this fn already exist in clojure? If not what would an idiomatic name be for it from Haskell or CL? I don't think it exists in clojure.core or clojure.contrib. --Chouser --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Clojure group. To post to this group, send email to clojure@googlegroups.com To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en -~--~~~~--~~--~--~---
Re: What is this function called?
On Thu, Jan 1, 2009 at 10:14 PM, Andrew Baine andrew.ba...@gmail.com wrote: I want to get a seq of successive rests of the given seq: user (defn f [seq] (if (empty? seq) nil (lazy-cons seq (f (rest seq) #'user/f user (f '(1 2 3 4)) ((1 2 3 4) (2 3 4) (3 4) (4)) Hi, Haskell has tails in the Data.List module which is similar, though it includes a null-list as a final value: *Main Data.List.tails [1..4] [[1,2,3,4],[2,3,4],[3,4],[4],[]] *Main take 10 . map (take 5) . Data.List.tails $ iterate (+1) 1 [[1,2,3,4,5],[2,3,4,5,6],[3,4,5,6,7],[4,5,6,7,8],[5,6,7,8,9],[6,7,8,9,10],[7,8,9,10,11],[8,9,10,11,12],[9,10,11,12,13],[10,11,12,13,14]] Rests makes good sense as a Clojure-name, IMO, as does not including a null-value at the end. Graham user (take 10 (map #(take 5 %) (f (iterate inc 1 ((1 2 3 4 5) (2 3 4 5 6) (3 4 5 6 7) (4 5 6 7 8) (5 6 7 8 9) (6 7 8 9 10) (7 8 9 10 11) (8 9 10 11 12) (9 10 11 12 13) (10 11 12 13 14)) Does this fn already exist in clojure? If not what would an idiomatic name be for it from Haskell or CL? Andrew --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Clojure group. To post to this group, send email to clojure@googlegroups.com To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en -~--~~~~--~~--~--~---
Re: What is this function called?
I did something similar using (iterate rest coll), which I called iter- rest: (defn iter-rest Takes the first (count coll) items from call to (iterate rest coll). If passed function as first argument, calls it on each invocation of rest, i.e. (iterate #(func (rest %)) coll). ([coll] (take (count coll) (iterate rest coll))) ([func coll] (take (count coll) (iterate #(func (rest %)) coll user= (iter-rest (range 3)) ((0 1 2) (1 2) (2)) I now realize a key difference is that, by using (count coll), iter- rest fully realizes anything lazy; for Andrew's lazy version above, I second the name rests. Perry --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Clojure group. To post to this group, send email to clojure@googlegroups.com To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en -~--~~~~--~~--~--~---
Re: What is this function called?
On Fri, Jan 2, 2009 at 8:09 AM, Perry Trolard trol...@gmail.com wrote: I did something similar using (iterate rest coll), which I called iter- rest: (defn iter-rest Takes the first (count coll) items from call to (iterate rest coll). If passed function as first argument, calls it on each invocation of rest, i.e. (iterate #(func (rest %)) coll). ([coll] (take (count coll) (iterate rest coll))) ([func coll] (take (count coll) (iterate #(func (rest %)) coll user= (iter-rest (range 3)) ((0 1 2) (1 2) (2)) I now realize a key difference is that, by using (count coll), iter- rest fully realizes anything lazy; for Andrew's lazy version above, I second the name rests. Perry Okay, great, I'm using it and calling it rests. Thanks all. --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Clojure group. To post to this group, send email to clojure@googlegroups.com To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en -~--~~~~--~~--~--~---
Re: What is this function called?
I don't know if the function exists on its own in Common Lisp, but in Common Lisp there is maplist that does what you get by combining map and rests : http://www.lispworks.com/documentation/HyperSpec/Body/f_mapc_.htm HTH, -- Laurent On Jan 2, 7:21 pm, Andrew Baine andrew.ba...@gmail.com wrote: On Fri, Jan 2, 2009 at 8:09 AM, Perry Trolard trol...@gmail.com wrote: I did something similar using (iterate rest coll), which I called iter- rest: (defn iter-rest Takes the first (count coll) items from call to (iterate rest coll). If passed function as first argument, calls it on each invocation of rest, i.e. (iterate #(func (rest %)) coll). ([coll] (take (count coll) (iterate rest coll))) ([func coll] (take (count coll) (iterate #(func (rest %)) coll user= (iter-rest (range 3)) ((0 1 2) (1 2) (2)) I now realize a key difference is that, by using (count coll), iter- rest fully realizes anything lazy; for Andrew's lazy version above, I second the name rests. Perry Okay, great, I'm using it and calling it rests. Thanks all. --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Clojure group. To post to this group, send email to clojure@googlegroups.com To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en -~--~~~~--~~--~--~---
What is this function called?
I want to get a seq of successive rests of the given seq: user (defn f [seq] (if (empty? seq) nil (lazy-cons seq (f (rest seq) #'user/f user (f '(1 2 3 4)) ((1 2 3 4) (2 3 4) (3 4) (4)) user (take 10 (map #(take 5 %) (f (iterate inc 1 ((1 2 3 4 5) (2 3 4 5 6) (3 4 5 6 7) (4 5 6 7 8) (5 6 7 8 9) (6 7 8 9 10) (7 8 9 10 11) (8 9 10 11 12) (9 10 11 12 13) (10 11 12 13 14)) Does this fn already exist in clojure? If not what would an idiomatic name be for it from Haskell or CL? Andrew --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Clojure group. To post to this group, send email to clojure@googlegroups.com To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en -~--~~~~--~~--~--~---
