B. Pym wrote:

Wow: loop macro rulez, somehow..
just one correction:
(loop for (a b c d) on (list 1 2 3 4 5 6 7 8) by #'cddddr
sum a into a-sum
sum b into b-sum
sum c into c-sum
sum d into d-sum
finally (return (list a-sum b-sum c-sum d-sum)))
Yeah, i might consider this code as beautiful
olivier

Gauche Scheme

(use gauche.lazy)
(use util.match)

(define data (lrange 1 57))

(match (lslices data 4)
[((a b c d) ...)
(map (cut fold + 0 <>)
(list a b c d))])

(378 392 406 420)

newLISP

(define data (sequence 1 56))

(map (curry apply +) (transpose (explode data 4)))

===>
(378 392 406 420)


Another way.

;; Using "apply" for "reduce". The 3rd argument tells
;; apply how many items to process at a time.
(apply
(fn (sums) (map + sums $args))
(cons '(0 0 0 0) data)
5)

--->
(378 392 406 420)

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 2024-08-30, B. Pym <Nobody447095@here-nor-there.org> wrote:

I'm just wondering if there is a lispier way to scan once through a
list and add each n'th item with n+constant.
Like kind of apply a list through a vector..
In my approach i just used the loop macro:
(defparameter vals '(1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1
2 3 4 5 6 7 8))

...

CL-USER> (sum-values vals)
(4 8 12 16 20 24 28 32)

Can you do better? (i hope you do and I am prepared to bear the shame)

I see that you ask to "scan once" but still feel awfully
tempted to reblock the data

CL-USER> (defun batch (list size)
(if (endp list)
'()
(cons (subseq list 0 size)
(batch (nthcdr size list) size))))
BATCH

CL-USER> (batch vals 8)

((1 2 3 4 5 6 7 8) (1 2 3 4 5 6 7 8) (1 2 3 4 5 6 7 8) (1 2 3 4 5 6 7 8))

CL-USER> (defun add (list)
(reduce (lambda(u v)(mapcar #'+ u v)) list))
ADD

CL-USER> (add (batch vals 8))
(4 8 12 16 20 24 28 32)

Mark Wooding wrote:

Or you could just do it the easy way:

(defun sum-every-softcore (period list)
(loop with sums = (make-array period :initial-element 0)
for item in list
for i = 0 then (mod (1+ i) period)
do (incf (aref sums i) item)
finally (return (coerce sums 'list))))

Gauche Scheme

(use srfi-42) ;; do-ec

(define (sum-every-nth n nlist)
(rlet1 result (make-vector n 0)
(do-ec (:list x (index i) nlist)
(inc! (vector-ref result (mod i n)) x))))

(define vals '(1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1
2 3 4 5 6 7 8))

(sum-every-nth 8 vals)

#(4 8 12 16 20 24 28 32)

This is the TXR Lisp interactive listener of TXR 296.
Quit with :quit or Ctrl-D on an empty line. Ctrl-X ? for cheatsheet.
TXR Lisp environments use genuine Saskatchewan sealskin bindings.

(flow '(1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8)

(tuples 8)
transpose
(mapcar sum))
(4 8 12 16 20 24 28 32)

--
TXR Programming Language: http://nongnu.org/txr
Cygnal: Cygwin Native Application Library: http://kylheku.com/cygnal
Mastodon: @Kazinator@mstdn.ca

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

I'm just wondering if there is a lispier way to scan once through a
list and add each n'th item with n+constant.
Like kind of apply a list through a vector..
In my approach i just used the loop macro:
(defparameter vals '(1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1
2 3 4 5 6 7 8))

...

CL-USER> (sum-values vals)
(4 8 12 16 20 24 28 32)

Can you do better? (i hope you do and I am prepared to bear the shame)

I see that you ask to "scan once" but still feel awfully
tempted to reblock the data

CL-USER> (defun batch (list size)
(if (endp list)
'()
(cons (subseq list 0 size)
(batch (nthcdr size list) size))))
BATCH

CL-USER> (batch vals 8)

((1 2 3 4 5 6 7 8) (1 2 3 4 5 6 7 8) (1 2 3 4 5 6 7 8) (1 2 3 4 5 6 7 8))

CL-USER> (defun add (list)
(reduce (lambda(u v)(mapcar #'+ u v)) list))
ADD

CL-USER> (add (batch vals 8))
(4 8 12 16 20 24 28 32)

Mark Wooding wrote:

Or you could just do it the easy way:

(defun sum-every-softcore (period list)
(loop with sums = (make-array period :initial-element 0)
for item in list
for i = 0 then (mod (1+ i) period)
do (incf (aref sums i) item)
finally (return (coerce sums 'list))))

Gauche Scheme

(use srfi-42) ;; do-ec

(define (sum-every-nth n nlist)
(rlet1 result (make-vector n 0)
(do-ec (:list x (index i) nlist)
(inc! (vector-ref result (mod i n)) x))))

(define vals '(1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1
2 3 4 5 6 7 8))

(sum-every-nth 8 vals)

#(4 8 12 16 20 24 28 32)

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)