Concatenate two lists in Common Lisp
I set myself to the task to write a Common Lisp function that concatenates two lists without using append.
Common Lisp input (concat-lists '(1 2 3) '(4 5 6)) should return (1 2 3 4 5 6)
Even though my solution seems to work it looks overtly complicated
(defun concat-lists(seq1 seq2)
(cond ((not (null seq1)) (cons (car seq1) (concat-lists (cdr seq1) seq2)))
(T (cond ((not (null seq2)) (cons (car seq2) (concat-lists seq1 (cdr seq2))))
(T nil)))))
What I'm looking for is a more elegant solution using reduce where I use seq1 as initial value and then apply a function to each element of seq2, thereby appending each value of the list to seq1. Somehow I always get stuck when trying....
Any help or input is much appreciated. Thanks!
lisp common-lisp
edited Nov 20 '18 at 23:39
Rainer Joswig
111k8169286
asked Nov 20 '18 at 22:51
lawrence313lawrence313
177
add a comment |
I set myself to the task to write a Common Lisp function that concatenates two lists without using append.
Common Lisp input (concat-lists '(1 2 3) '(4 5 6)) should return (1 2 3 4 5 6)
Even though my solution seems to work it looks overtly complicated
(defun concat-lists(seq1 seq2)
(cond ((not (null seq1)) (cons (car seq1) (concat-lists (cdr seq1) seq2)))
(T (cond ((not (null seq2)) (cons (car seq2) (concat-lists seq1 (cdr seq2))))
(T nil)))))
What I'm looking for is a more elegant solution using reduce where I use seq1 as initial value and then apply a function to each element of seq2, thereby appending each value of the list to seq1. Somehow I always get stuck when trying....
Any help or input is much appreciated. Thanks!
lisp common-lisp
edited Nov 20 '18 at 23:39
Rainer Joswig
111k8169286
asked Nov 20 '18 at 22:51
lawrence313lawrence313
177
add a comment |
I set myself to the task to write a Common Lisp function that concatenates two lists without using append.
Common Lisp input (concat-lists '(1 2 3) '(4 5 6)) should return (1 2 3 4 5 6)
Even though my solution seems to work it looks overtly complicated
(defun concat-lists(seq1 seq2)
(cond ((not (null seq1)) (cons (car seq1) (concat-lists (cdr seq1) seq2)))
(T (cond ((not (null seq2)) (cons (car seq2) (concat-lists seq1 (cdr seq2))))
(T nil)))))
What I'm looking for is a more elegant solution using reduce where I use seq1 as initial value and then apply a function to each element of seq2, thereby appending each value of the list to seq1. Somehow I always get stuck when trying....
Any help or input is much appreciated. Thanks!
lisp common-lisp
edited Nov 20 '18 at 23:39
Rainer Joswig
111k8169286
asked Nov 20 '18 at 22:51
lawrence313lawrence313
177
I set myself to the task to write a Common Lisp function that concatenates two lists without using append.
Common Lisp input (concat-lists '(1 2 3) '(4 5 6)) should return (1 2 3 4 5 6)
Even though my solution seems to work it looks overtly complicated
(defun concat-lists(seq1 seq2)
(cond ((not (null seq1)) (cons (car seq1) (concat-lists (cdr seq1) seq2)))
(T (cond ((not (null seq2)) (cons (car seq2) (concat-lists seq1 (cdr seq2))))
(T nil)))))
What I'm looking for is a more elegant solution using reduce where I use seq1 as initial value and then apply a function to each element of seq2, thereby appending each value of the list to seq1. Somehow I always get stuck when trying....
Any help or input is much appreciated. Thanks!
lisp common-lisp
lisp common-lisp
edited Nov 20 '18 at 23:39
Rainer Joswig
111k8169286
asked Nov 20 '18 at 22:51
lawrence313lawrence313
177
edited Nov 20 '18 at 23:39
Rainer Joswig
111k8169286
asked Nov 20 '18 at 22:51
lawrence313lawrence313
177
edited Nov 20 '18 at 23:39
Rainer Joswig
111k8169286
edited Nov 20 '18 at 23:39
Rainer Joswig
111k8169286
edited Nov 20 '18 at 23:39
Rainer Joswig
111k8169286
111k8169286
asked Nov 20 '18 at 22:51
lawrence313lawrence313
177
asked Nov 20 '18 at 22:51
lawrence313lawrence313
177
asked Nov 20 '18 at 22:51
lawrence313lawrence313
177
177
add a comment |
add a comment |
3 Answers
3
active
oldest
votes
CL-USER 39 > (reduce #'cons
'(1 2 3 4 5)
:initial-value '(a b c d e)
:from-end t)
(1 2 3 4 5 A B C D E)
answered Nov 20 '18 at 23:46
Rainer JoswigRainer Joswig
111k8169286
seems so obvious now... thanks!
– lawrence313
Nov 21 '18 at 0:15
add a comment |
The solution of Rainer Joswig is really elegant and simple, and respects your request of using reduce.
If you want to see also a recursive, simple solution, then here is the classical one:
(defun concat-lists (seq1 seq2)
(if (null seq1)
seq2
(cons (car seq1) (concat-lists (cdr seq1) seq2))))
(concat-lists '(1 2 3) '(4 5 6))
(1 2 3 4 5 6)
answered Nov 21 '18 at 10:25
RenzoRenzo
18k43043
add a comment |
I do understand your requirement for 'reduce'. and here other options:
CL also has 'concatenante'
(concatenate 'list '(1 2 3) '(4 5 6))
There is also the other less complicated (IMHO), and not as elegant.
(defun concat-lists (list1 list2)
(let ((a (copy-list list1))
(b (copy-list list2)))
(rplacd (last a) b)
a))
or
(defun concat-lists (list1 list2)
(let ((a (copy-list list1))
(b (copy-list list2)))
(nconc a b)))
answered Nov 23 '18 at 22:42
Ala'a MohammadAla'a Mohammad
8124
1
There is no need to copylist2in both your functions, since it will not be modified.
– Renzo
Nov 25 '18 at 10:27
add a comment |
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3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
CL-USER 39 > (reduce #'cons
'(1 2 3 4 5)
:initial-value '(a b c d e)
:from-end t)
(1 2 3 4 5 A B C D E)
answered Nov 20 '18 at 23:46
Rainer JoswigRainer Joswig
111k8169286
seems so obvious now... thanks!
– lawrence313
Nov 21 '18 at 0:15
add a comment |
CL-USER 39 > (reduce #'cons
'(1 2 3 4 5)
:initial-value '(a b c d e)
:from-end t)
(1 2 3 4 5 A B C D E)
answered Nov 20 '18 at 23:46
Rainer JoswigRainer Joswig
111k8169286
seems so obvious now... thanks!
– lawrence313
Nov 21 '18 at 0:15
add a comment |
CL-USER 39 > (reduce #'cons
'(1 2 3 4 5)
:initial-value '(a b c d e)
:from-end t)
(1 2 3 4 5 A B C D E)
answered Nov 20 '18 at 23:46
Rainer JoswigRainer Joswig
111k8169286
CL-USER 39 > (reduce #'cons
'(1 2 3 4 5)
:initial-value '(a b c d e)
:from-end t)
(1 2 3 4 5 A B C D E)
answered Nov 20 '18 at 23:46
Rainer JoswigRainer Joswig
111k8169286
answered Nov 20 '18 at 23:46
Rainer JoswigRainer Joswig
111k8169286
answered Nov 20 '18 at 23:46
Rainer JoswigRainer Joswig
111k8169286
answered Nov 20 '18 at 23:46
Rainer JoswigRainer Joswig
111k8169286
111k8169286
seems so obvious now... thanks!
– lawrence313
Nov 21 '18 at 0:15
add a comment |
seems so obvious now... thanks!
– lawrence313
Nov 21 '18 at 0:15
seems so obvious now... thanks!
– lawrence313
Nov 21 '18 at 0:15
seems so obvious now... thanks!
– lawrence313
Nov 21 '18 at 0:15
add a comment |
The solution of Rainer Joswig is really elegant and simple, and respects your request of using reduce.
If you want to see also a recursive, simple solution, then here is the classical one:
(defun concat-lists (seq1 seq2)
(if (null seq1)
seq2
(cons (car seq1) (concat-lists (cdr seq1) seq2))))
(concat-lists '(1 2 3) '(4 5 6))
(1 2 3 4 5 6)
answered Nov 21 '18 at 10:25
RenzoRenzo
18k43043
add a comment |
The solution of Rainer Joswig is really elegant and simple, and respects your request of using reduce.
If you want to see also a recursive, simple solution, then here is the classical one:
(defun concat-lists (seq1 seq2)
(if (null seq1)
seq2
(cons (car seq1) (concat-lists (cdr seq1) seq2))))
(concat-lists '(1 2 3) '(4 5 6))
(1 2 3 4 5 6)
answered Nov 21 '18 at 10:25
RenzoRenzo
18k43043
add a comment |
The solution of Rainer Joswig is really elegant and simple, and respects your request of using reduce.
If you want to see also a recursive, simple solution, then here is the classical one:
(defun concat-lists (seq1 seq2)
(if (null seq1)
seq2
(cons (car seq1) (concat-lists (cdr seq1) seq2))))
(concat-lists '(1 2 3) '(4 5 6))
(1 2 3 4 5 6)
answered Nov 21 '18 at 10:25
RenzoRenzo
18k43043
The solution of Rainer Joswig is really elegant and simple, and respects your request of using reduce.
If you want to see also a recursive, simple solution, then here is the classical one:
(defun concat-lists (seq1 seq2)
(if (null seq1)
seq2
(cons (car seq1) (concat-lists (cdr seq1) seq2))))
(concat-lists '(1 2 3) '(4 5 6))
(1 2 3 4 5 6)
answered Nov 21 '18 at 10:25
RenzoRenzo
18k43043
edited Nov 21 '18 at 15:04
answered Nov 21 '18 at 10:25
RenzoRenzo
18k43043
answered Nov 21 '18 at 10:25
RenzoRenzo
18k43043
answered Nov 21 '18 at 10:25
RenzoRenzo
18k43043
18k43043
add a comment |
add a comment |
I do understand your requirement for 'reduce'. and here other options:
CL also has 'concatenante'
(concatenate 'list '(1 2 3) '(4 5 6))
There is also the other less complicated (IMHO), and not as elegant.
(defun concat-lists (list1 list2)
(let ((a (copy-list list1))
(b (copy-list list2)))
(rplacd (last a) b)
a))
or
(defun concat-lists (list1 list2)
(let ((a (copy-list list1))
(b (copy-list list2)))
(nconc a b)))
answered Nov 23 '18 at 22:42
Ala'a MohammadAla'a Mohammad
8124
1
There is no need to copylist2in both your functions, since it will not be modified.
– Renzo
Nov 25 '18 at 10:27
add a comment |
I do understand your requirement for 'reduce'. and here other options:
CL also has 'concatenante'
(concatenate 'list '(1 2 3) '(4 5 6))
There is also the other less complicated (IMHO), and not as elegant.
(defun concat-lists (list1 list2)
(let ((a (copy-list list1))
(b (copy-list list2)))
(rplacd (last a) b)
a))
or
(defun concat-lists (list1 list2)
(let ((a (copy-list list1))
(b (copy-list list2)))
(nconc a b)))
answered Nov 23 '18 at 22:42
Ala'a MohammadAla'a Mohammad
8124
1
There is no need to copylist2in both your functions, since it will not be modified.
– Renzo
Nov 25 '18 at 10:27
add a comment |
I do understand your requirement for 'reduce'. and here other options:
CL also has 'concatenante'
(concatenate 'list '(1 2 3) '(4 5 6))
There is also the other less complicated (IMHO), and not as elegant.
(defun concat-lists (list1 list2)
(let ((a (copy-list list1))
(b (copy-list list2)))
(rplacd (last a) b)
a))
or
(defun concat-lists (list1 list2)
(let ((a (copy-list list1))
(b (copy-list list2)))
(nconc a b)))
answered Nov 23 '18 at 22:42
Ala'a MohammadAla'a Mohammad
8124
I do understand your requirement for 'reduce'. and here other options:
CL also has 'concatenante'
(concatenate 'list '(1 2 3) '(4 5 6))
There is also the other less complicated (IMHO), and not as elegant.
(defun concat-lists (list1 list2)
(let ((a (copy-list list1))
(b (copy-list list2)))
(rplacd (last a) b)
a))
or
(defun concat-lists (list1 list2)
(let ((a (copy-list list1))
(b (copy-list list2)))
(nconc a b)))
answered Nov 23 '18 at 22:42
Ala'a MohammadAla'a Mohammad
8124
edited Nov 24 '18 at 14:21
answered Nov 23 '18 at 22:42
Ala'a MohammadAla'a Mohammad
8124
answered Nov 23 '18 at 22:42
Ala'a MohammadAla'a Mohammad
8124
answered Nov 23 '18 at 22:42
Ala'a MohammadAla'a Mohammad
8124
8124
1
There is no need to copylist2in both your functions, since it will not be modified.
– Renzo
Nov 25 '18 at 10:27
add a comment |
1
There is no need to copylist2in both your functions, since it will not be modified.
– Renzo
Nov 25 '18 at 10:27
1
1
There is no need to copy
list2 in both your functions, since it will not be modified.– Renzo
Nov 25 '18 at 10:27
There is no need to copy
list2 in both your functions, since it will not be modified.– Renzo
Nov 25 '18 at 10:27
add a comment |
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