Hi Stephen,
thanks for yoru reply ! ::)
At the certain point of the program I get
a list as parameter 'lst', which contains
the sublists of strings. I wrote this
function:
(define (to-txt lst)
(if (empty? lst)
lst
(let ((line (car lst)))
(begin
(displayln (apply string-join line " " )) ;;; WRONG SYNTAX HERE
(to-txt (cdr lst))))))
Since I get the sublists as parameters I need an 'apply' to 'inject'
(sorry...I am no native speaker...) 'string-join' into the list.
But string-join has additional parameters, and I dont know how to
combine those with 'apply'?
PS: The resulting strings will later be processed further... the
'displayln' is just a placeholder...
Cheers,
Meino
Stephen Chang <stch...@ccs.neu.edu> [16-10-29 17:16]:
> string-join already expects a list of strings, so are you sure you want apply?
> Can you give a more specific example?
>
> Perhaps map or some other iteration is what you want?
>
> (for ([strs '(("a" "b") ("c" "D" "E"))])
> (displayln (string-join strs " ")))
>
> =>
> a b
> c D E
>
> On Sat, Oct 29, 2016 at 10:27 AM, <meino.cra...@gmx.de> wrote:
> > Hi,
> >
> > ...still improving my shortwave-broadcaster-dumper... :)
> >
> > I have a list with sublists of strings, which I want to concatenate.
> > Each sublist shall form one line of output.
> > I tried 'string-append', but this gives me something like this
> > (excerpt):
> > "189RikisutvarpidRas1+20000-24001234567Icelandic"
> > ...the separating #\space is missing.
> >
> > The according code looks like this (excerpt)
> >
> > (apply string-append sublist)
> >
> > then I found 'string-join' which has extra-parameters
> > to define separator of all kinds.
> >
> > ...but...how can I express the 'apply'-instruction...with the
> > addional parameters???
> >
> > This looks something inbetween funny and weird:
> >
> > (apply string-join sublist " ")
> >
> > and racket mumbles:
> > apply: contract violation
> > expected: list?
> > given: " "
> > argument position: 3rd
> > other arguments...:
> > #<procedure:string-join>
> >
> >
> > ?
> >
> > Cheers
> > Meino
> >
> >
> >
> >
> >
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