GOOPS with variable number of arguments

GOOPS with variable number of arguments

[Jan Wedekind]

Hi,
I am trying to implement n-ary operations for different types of objects.
When specialising "+" for two arguments, it will automatically work on 
more arguments.

     (use-modules (oop goops) (srfi srfi-1))
     (define-generic +)
     (define-method (+ (a <string>) (b <string>)) (string-append a b))
     (+ "a" "b" "c")
     ; "abc"

However I have trouble figuring out a method definition for test which 
would result in the same behaviour.

     (define (test . args) ...)
     (define-generic test)
     (define-method (test (a <string>) (b <string>)) (string-append a b))
     (test "a" "b" "c")
     ; "abc"

Please let me know if there is a solution.

Re: GOOPS with variable number of arguments

[David Kastrup]

[-- Attachment #1: Type: text/plain, Size: 732 bytes --]

Jan Wedekind <jan@wedesoft.de> writes:

> Hi,
> I am trying to implement n-ary operations for different types of objects.
> When specialising "+" for two arguments, it will automatically work on
> more arguments.
>
>     (use-modules (oop goops) (srfi srfi-1))
>     (define-generic +)
>     (define-method (+ (a <string>) (b <string>)) (string-append a b))
>     (+ "a" "b" "c")
>     ; "abc"
>
> However I have trouble figuring out a method definition for test which
> would result in the same behaviour.
>
>     (define (test . args) ...)
>     (define-generic test)
>     (define-method (test (a <string>) (b <string>)) (string-append a b))
>     (test "a" "b" "c")
>     ; "abc"
>
> Please let me know if there is a solution.


[-- Attachment #2: bab.scm --]
[-- Type: text/plain, Size: 276 bytes --]

(use-modules (oop goops))

(define-generic test)
(define-method (test a b c . rest)
  (if (null? rest) (test (test a b) c)
      (apply test (test (test a b) c) rest)))
(define-method (test (a <string>) (b <string>)) (string-append a b))

(display (test "a" "b" "c" "d" "e"))

[-- Attachment #3: Type: text/plain, Size: 20 bytes --]



-- 
David Kastrup

Re: GOOPS with variable number of arguments

[Jan Wedekind]

Ok, thanks. I'll use that solution.

On Sat, 28 Nov 2015, David Kastrup wrote:

> Jan Wedekind <jan@wedesoft.de> writes:
>
>> Hi,
>> I am trying to implement n-ary operations for different types of objects.
>> When specialising "+" for two arguments, it will automatically work on
>> more arguments.
>>
>>     (use-modules (oop goops) (srfi srfi-1))
>>     (define-generic +)
>>     (define-method (+ (a <string>) (b <string>)) (string-append a b))
>>     (+ "a" "b" "c")
>>     ; "abc"
>>
>> However I have trouble figuring out a method definition for test which
>> would result in the same behaviour.
>>
>>     (define (test . args) ...)
>>     (define-generic test)
>>     (define-method (test (a <string>) (b <string>)) (string-append a b))
>>     (test "a" "b" "c")
>>     ; "abc"
>>
>> Please let me know if there is a solution.
>
>