• #### Re: Remove part of a list

From B. Pym@21:1/5 to All on Sat Jul 20 16:23:20 2024
I have this list = '((8 2) (8 3) (8 4) (7 4) (6 4) (5 4) (4 4)
(4 5) (3 5) (3 6) (4 6) (4 5) (4 4) (5 4) (6 4) (7 4) (8 4)
(8 5) (9 5) (10 5))

And i want to remove the part os list that begin in '(8 4) to
the '(8 4)..

The result sould be this: = '((8 2) (8 3) (8 4) (8 5) (9 5) (10 5))

It looks as if the resulting sequence is the longest subsequence of
the original sequence, in which the sums of the value pairs are
strictly increasing.

Can anyone help me?

Maybe this?

(defun strictly-increasing (input-pair-list)
(loop with max = nil
for pair in input-pair-list
for pair-value = (apply #'+ pair)
when (or (null max) (> pair-value max))
collect pair and
do (setf max pair-value))))

Testing in SBCL:

(defun strictly-increasing (input-pair-list)
(loop with max = nil
for pair in input-pair-list
for pair-value = (apply #'+ pair)
when (or (null max) (> pair-value max))
collect pair and
do (setf max pair-value))))

STRICTLY-INCREASING
*
unmatched close parenthesis

(strictly-increasing
'((8 2) (8 3) (8 4) (7 4) (6 4) (5 4) (4 4)
(4 5) (3 5) (3 6) (4 6) (4 5) (4 4) (5 4) (6 4) (7 4) (8 4)
(8 5) (9 5) (10 5)))
===>
((8 2) (8 3) (8 4) (8 5) (9 5) (10 5))

Gauche Scheme

(define (strictly-increasing couples)
(let1 n #f
(filter
(^c (let1 sum (apply + c)
(and (or (not n) (> sum n)) (set! n sum))))
couples)))

(strictly-increasing
'((8 2) (8 3) (8 4) (7 4) (6 4) (5 4) (4 4)
(4 5) (3 5) (3 6) (4 6) (4 5) (4 4) (5 4) (6 4) (7 4) (8 4)
(8 5) (9 5) (10 5)))

===>
((8 2) (8 3) (8 4) (8 5) (9 5) (10 5))

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• From Kaz Kylheku@21:1/5 to B. Pym on Sat Jul 20 21:07:23 2024
On 2024-07-20, B. Pym <Nobody447095@here-nor-there.org> wrote:
I have this list = '((8 2) (8 3) (8 4) (7 4) (6 4) (5 4) (4 4)
(4 5) (3 5) (3 6) (4 6) (4 5) (4 4) (5 4) (6 4) (7 4) (8 4)
(8 5) (9 5) (10 5))

And i want to remove the part os list that begin in '(8 4) to
the '(8 4)..

The result sould be this: = '((8 2) (8 3) (8 4) (8 5) (9 5) (10 5))

It looks as if the resulting sequence is the longest subsequence of
the original sequence, in which the sums of the value pairs are
strictly increasing.

Can anyone help me?

Maybe this?

(defun strictly-increasing (input-pair-list)
(loop with max = nil
for pair in input-pair-list
for pair-value = (apply #'+ pair)
when (or (null max) (> pair-value max))
collect pair and
do (setf max pair-value))))

Testing in SBCL:

(defun strictly-increasing (input-pair-list)
(loop with max = nil
for pair in input-pair-list
for pair-value = (apply #'+ pair)
when (or (null max) (> pair-value max))
collect pair and
do (setf max pair-value))))

STRICTLY-INCREASING
*
unmatched close parenthesis

(strictly-increasing
'((8 2) (8 3) (8 4) (7 4) (6 4) (5 4) (4 4)
(4 5) (3 5) (3 6) (4 6) (4 5) (4 4) (5 4) (6 4) (7 4) (8 4)
(8 5) (9 5) (10 5)))

((8 2) (8 3) (8 4) (8 5) (9 5) (10 5))

Gauche Scheme

(define (strictly-increasing couples)
(let1 n #f
(filter
(^c (let1 sum (apply + c)
(and (or (not n) (> sum n)) (set! n sum))))
couples)))

(strictly-increasing
'((8 2) (8 3) (8 4) (7 4) (6 4) (5 4) (4 4)
(4 5) (3 5) (3 6) (4 6) (4 5) (4 4) (5 4) (6 4) (7 4) (8 4)
(8 5) (9 5) (10 5)))

((8 2) (8 3) (8 4) (8 5) (9 5) (10 5))

Simple pop in a loop and conditionally collect.

(defun strictly-increasing (lists)
(build (iflet ((list (pop lists)))
(let ((val (sum list)))
(whilet ((list (pop lists)))
(whena (> (sum list) val)
(set val it)
strictly-increasing
(strictly-increasing
'((8 2) (8 3) (8 4) (7 4) (6 4) (5 4) (4 4)
(4 5) (3 5) (3 6) (4 6) (4 5) (4 4) (5 4) (6 4) (7 4) (8 4)
(8 5) (9 5) (10 5)))
((8 2) (8 3) (8 4) (8 5) (9 5) (10 5))

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

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