Hi Ken,
thanks for your reply ! :)
The problem is much "simpler"... :)
You wrote the whole logic to dig into the strings in the sublists in
the big list.
That's already done and working
I am in search for doing this
(string-join '( "a" "b" "c") " " ) ;; ( "a" "b" "c") is the sublist
but in the context of apply:
(define (to-txt lst)
(if (empty? lst)
lst
(let ((line (car lst)))
(begin
(displayln (apply string-join line " ")) ;; THIS IS THE WRONG SYNTAX!!!
(to-txt (cdr lst))))))
...and printing the lines is only a intermediate result....the joined
strings will be processed further in a later stage of this program.
That's why I need a complete string with separators.
Cheers
Meino
Ken MacKenzie <deviloc...@gmail.com> [16-10-29 16:48]:
> Not 100% sure of what you're asking so if I got this wrong pseudo code it for
> me. Remember I am kind of new to racket but I will give it a go:
>
> As I understand it you have a list of lists of strings perhaps like this...
>
> (('this' 'is' 'one')('this' 'is' 'another')....('this' 'is' 'the' 'last'))
>
> and you want to output as such
>
> this is one
> this is another
> ....
> this is the last
>
>
> Ok so here is how I would do this
>
> I will write this as 2 functions, from your main code you call the first
> passing it ...
>
> big-list = the whole list of lists
>
> ;;in main loop
> (per-line big-list)
>
> (define (per-line blist)
> (cond
> [(empty? blist) #f]
> [else
> (per-item (first blist))
> (newline)
> (per-line (rest blist))]))
>
> (define (per-item slist)
> (cond
> [(empty? slist) #f]
> [else
> (display (first slist))
> (display " ")
> (per-item (rest slist))]))
>
> That should be about it. Double check me an ide about matched parens and
> brackets. I just eyeballed this real quick in the message. But that is the
> approach I would take for a simple proof.
>
> An alternate approach is per-item accepts a string argument and returns the
> string to per-line to display. But if the end goal is quick output this is a
> bout as concise + readable as I think I can make it.
>
> Ken
>
>
> On Saturday, October 29, 2016 at 10:27:09 AM UTC-4, meino.cramer 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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