Mixing
sum of a list in scheme
I'm beginner in functional programming and scheme language.
I found a way to build the sum of a list:
(define (sum lst)
(if (empty? lst)
0
(+ (car lst) (sum (cdr lst)))))
(sum (list 1 2 3))
My question is: is there a way to build the sum of a list without a extra function like sum, just using the "+" function like this:
(+ 1 2 3)
scheme racket
edited Feb 3 '18 at 19:07
Mat
166k29318348
asked Feb 3 '18 at 19:05
SergeSerge
162
add a comment |
I'm beginner in functional programming and scheme language.
I found a way to build the sum of a list:
(define (sum lst)
(if (empty? lst)
0
(+ (car lst) (sum (cdr lst)))))
(sum (list 1 2 3))
My question is: is there a way to build the sum of a list without a extra function like sum, just using the "+" function like this:
(+ 1 2 3)
scheme racket
edited Feb 3 '18 at 19:07
Mat
166k29318348
asked Feb 3 '18 at 19:05
SergeSerge
162
add a comment |
I'm beginner in functional programming and scheme language.
I found a way to build the sum of a list:
(define (sum lst)
(if (empty? lst)
0
(+ (car lst) (sum (cdr lst)))))
(sum (list 1 2 3))
My question is: is there a way to build the sum of a list without a extra function like sum, just using the "+" function like this:
(+ 1 2 3)
scheme racket
edited Feb 3 '18 at 19:07
Mat
166k29318348
asked Feb 3 '18 at 19:05
SergeSerge
162
I'm beginner in functional programming and scheme language.
I found a way to build the sum of a list:
(define (sum lst)
(if (empty? lst)
0
(+ (car lst) (sum (cdr lst)))))
(sum (list 1 2 3))
My question is: is there a way to build the sum of a list without a extra function like sum, just using the "+" function like this:
(+ 1 2 3)
scheme racket
scheme racket
edited Feb 3 '18 at 19:07
Mat
166k29318348
asked Feb 3 '18 at 19:05
SergeSerge
162
edited Feb 3 '18 at 19:07
Mat
166k29318348
asked Feb 3 '18 at 19:05
SergeSerge
162
edited Feb 3 '18 at 19:07
Mat
166k29318348
edited Feb 3 '18 at 19:07
Mat
166k29318348
edited Feb 3 '18 at 19:07
Mat
166k29318348
166k29318348
asked Feb 3 '18 at 19:05
SergeSerge
162
asked Feb 3 '18 at 19:05
SergeSerge
162
asked Feb 3 '18 at 19:05
SergeSerge
162
162
add a comment |
add a comment |
3 Answers
3
active
oldest
votes
You can apply list of arguments to a function. So in this case you can:
> (apply + (list 1 2 3))
6
answered Feb 3 '18 at 19:22
rsmrsm
1,26631623
add a comment |
The reference for MIT/Gnu-Scheme says, that + takes ANY number of arguments.
I am sure, that this standard.
In general:
(define (foo . args) ....)
is used like (foo) or (foo x) or (foo x y), (foo x y z), .... . Inside foo the args will be '(), (x), (x y) or (x y z).
See exercise 2.20 in SICP or MIT/Scheme Reference 9.2 chap 2.1
This means:
For the arithmetic procedures +, *, - and / your procedure is not necessary, because they are defined for any number of arguments, including zero and one.
This is also true for some other built-in procedures.
For your own procedures you can use the dotted-tail notation.
You can download the MIT/Scheme Reference from the GNU-Pages. I think it helps for all implementation of Scheme, because extension of the standard are
described. Most parts are easy to read.
edited Jan 2 at 3:57
rsm
1,26631623
answered Feb 3 '18 at 22:47
Georg FussGeorg Fuss
1778
add a comment |
Common Lisp programmers should look to
[http://www.gigamonkeys.com/book/functions.html].
Here you must use &rest instead of >.<
(defun + (&rest numbers) ...)
Both lisp-dialects know default, optional and rest parameters.
answered Feb 4 '18 at 22:42
Georg FussGeorg Fuss
1778
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
You can apply list of arguments to a function. So in this case you can:
> (apply + (list 1 2 3))
6
answered Feb 3 '18 at 19:22
rsmrsm
1,26631623
add a comment |
You can apply list of arguments to a function. So in this case you can:
> (apply + (list 1 2 3))
6
answered Feb 3 '18 at 19:22
rsmrsm
1,26631623
add a comment |
You can apply list of arguments to a function. So in this case you can:
> (apply + (list 1 2 3))
6
answered Feb 3 '18 at 19:22
rsmrsm
1,26631623
You can apply list of arguments to a function. So in this case you can:
> (apply + (list 1 2 3))
6
answered Feb 3 '18 at 19:22
rsmrsm
1,26631623
answered Feb 3 '18 at 19:22
rsmrsm
1,26631623
answered Feb 3 '18 at 19:22
rsmrsm
1,26631623
answered Feb 3 '18 at 19:22
rsmrsm
1,26631623
1,26631623
add a comment |
add a comment |
The reference for MIT/Gnu-Scheme says, that + takes ANY number of arguments.
I am sure, that this standard.
In general:
(define (foo . args) ....)
is used like (foo) or (foo x) or (foo x y), (foo x y z), .... . Inside foo the args will be '(), (x), (x y) or (x y z).
See exercise 2.20 in SICP or MIT/Scheme Reference 9.2 chap 2.1
This means:
For the arithmetic procedures +, *, - and / your procedure is not necessary, because they are defined for any number of arguments, including zero and one.
This is also true for some other built-in procedures.
For your own procedures you can use the dotted-tail notation.
You can download the MIT/Scheme Reference from the GNU-Pages. I think it helps for all implementation of Scheme, because extension of the standard are
described. Most parts are easy to read.
edited Jan 2 at 3:57
rsm
1,26631623
answered Feb 3 '18 at 22:47
Georg FussGeorg Fuss
1778
add a comment |
The reference for MIT/Gnu-Scheme says, that + takes ANY number of arguments.
I am sure, that this standard.
In general:
(define (foo . args) ....)
is used like (foo) or (foo x) or (foo x y), (foo x y z), .... . Inside foo the args will be '(), (x), (x y) or (x y z).
See exercise 2.20 in SICP or MIT/Scheme Reference 9.2 chap 2.1
This means:
For the arithmetic procedures +, *, - and / your procedure is not necessary, because they are defined for any number of arguments, including zero and one.
This is also true for some other built-in procedures.
For your own procedures you can use the dotted-tail notation.
You can download the MIT/Scheme Reference from the GNU-Pages. I think it helps for all implementation of Scheme, because extension of the standard are
described. Most parts are easy to read.
edited Jan 2 at 3:57
rsm
1,26631623
answered Feb 3 '18 at 22:47
Georg FussGeorg Fuss
1778
add a comment |
The reference for MIT/Gnu-Scheme says, that + takes ANY number of arguments.
I am sure, that this standard.
In general:
(define (foo . args) ....)
is used like (foo) or (foo x) or (foo x y), (foo x y z), .... . Inside foo the args will be '(), (x), (x y) or (x y z).
See exercise 2.20 in SICP or MIT/Scheme Reference 9.2 chap 2.1
This means:
For the arithmetic procedures +, *, - and / your procedure is not necessary, because they are defined for any number of arguments, including zero and one.
This is also true for some other built-in procedures.
For your own procedures you can use the dotted-tail notation.
You can download the MIT/Scheme Reference from the GNU-Pages. I think it helps for all implementation of Scheme, because extension of the standard are
described. Most parts are easy to read.
edited Jan 2 at 3:57
rsm
1,26631623
answered Feb 3 '18 at 22:47
Georg FussGeorg Fuss
1778
The reference for MIT/Gnu-Scheme says, that + takes ANY number of arguments.
I am sure, that this standard.
In general:
(define (foo . args) ....)
is used like (foo) or (foo x) or (foo x y), (foo x y z), .... . Inside foo the args will be '(), (x), (x y) or (x y z).
See exercise 2.20 in SICP or MIT/Scheme Reference 9.2 chap 2.1
This means:
For the arithmetic procedures +, *, - and / your procedure is not necessary, because they are defined for any number of arguments, including zero and one.
This is also true for some other built-in procedures.
For your own procedures you can use the dotted-tail notation.
You can download the MIT/Scheme Reference from the GNU-Pages. I think it helps for all implementation of Scheme, because extension of the standard are
described. Most parts are easy to read.
edited Jan 2 at 3:57
rsm
1,26631623
answered Feb 3 '18 at 22:47
Georg FussGeorg Fuss
1778
edited Jan 2 at 3:57
rsm
1,26631623
edited Jan 2 at 3:57
rsm
1,26631623
edited Jan 2 at 3:57
rsm
1,26631623
1,26631623
answered Feb 3 '18 at 22:47
Georg FussGeorg Fuss
1778
answered Feb 3 '18 at 22:47
Georg FussGeorg Fuss
1778
answered Feb 3 '18 at 22:47
Georg FussGeorg Fuss
1778
1778
add a comment |
add a comment |
Common Lisp programmers should look to
[http://www.gigamonkeys.com/book/functions.html].
Here you must use &rest instead of >.<
(defun + (&rest numbers) ...)
Both lisp-dialects know default, optional and rest parameters.
answered Feb 4 '18 at 22:42
Georg FussGeorg Fuss
1778
add a comment |
Common Lisp programmers should look to
[http://www.gigamonkeys.com/book/functions.html].
Here you must use &rest instead of >.<
(defun + (&rest numbers) ...)
Both lisp-dialects know default, optional and rest parameters.
answered Feb 4 '18 at 22:42
Georg FussGeorg Fuss
1778
add a comment |
Common Lisp programmers should look to
[http://www.gigamonkeys.com/book/functions.html].
Here you must use &rest instead of >.<
(defun + (&rest numbers) ...)
Both lisp-dialects know default, optional and rest parameters.
answered Feb 4 '18 at 22:42
Georg FussGeorg Fuss
1778
Common Lisp programmers should look to
[http://www.gigamonkeys.com/book/functions.html].
Here you must use &rest instead of >.<
(defun + (&rest numbers) ...)
Both lisp-dialects know default, optional and rest parameters.
answered Feb 4 '18 at 22:42
Georg FussGeorg Fuss
1778
answered Feb 4 '18 at 22:42
Georg FussGeorg Fuss
1778
answered Feb 4 '18 at 22:42
Georg FussGeorg Fuss
1778
answered Feb 4 '18 at 22:42
Georg FussGeorg Fuss
1778
1778
add a comment |
add a comment |
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