On Monday, October 5, 2015 at 2:04:16 AM UTC-7, Paolo Giarrusso wrote:
> On Monday, October 5, 2015 at 1:07:31 AM UTC+2, Josh English wrote:
> > I am trying to learn Racket by creating a Todo manager based on the
> > Todo.txt format by Gina Trapani (http://todotxt.com/)
> >
> > I also have an Android tablet that uses a todo.txt application. This
> > application uses "\n\r" at the end of each line. I'm on Windows 7, so I
> > need this newline to work as well, because if I open the file up in
> > Notepad, it messes up my lines and my todos (normally one per line) become
> > one multi-line todo.
> >
> > The program reads the text file using file->lines and filters any blank
> > lines.
> >
> > The program writes the text file and I manually write the "\n\r" using
> > write, display, and print. That is to say, I've tried all three and ended
> > up with extra "\n" characters.
> >
> > Here is a snippet from my do-task procedure:
> >
> > (with-output-to-file (task-file-path) #:mode 'text #:exists
> > 'truncate/replace
> > (lambda ()
> > (write (string-join (drop-right uptos 1) "\n\r"))
> > (write "\n\r")
> > (write (complete-task (last uptos) (rest taskstuff)))
> > (write "\n\r")
> > (write (string-join afters "\n\r")
> >
> > When I open the file with SciTe, it shows the CR and LF characters at the
> > end of each line, plus a blank line with a CR character.
> >
> > The complite-task procedure transforms a task and returns a trimmed string.
> >
> > Where is this extra blank line coming from?
> >
> > Full draft code at http://pastebin.com/z3C5BQJP
> >
> > Thanks,
> >
> > Josh
>
> It's from #:mode 'text, that translates \n to \r\n: this way, programs can
> end the line with \n on all platforms, yet produce the right end-of-line on
> Windows. This behavior is copied from the C libraries. BTW, are you sure you
> want \n\r? That means LF CR, while on Windows you want \r\n.
>
> To sum up: You can either use #:mode 'text and just use \n (which will
> produce native end-of-lines, hence will produce the format you want only on
> Windows) *or* specify #:mode 'binary and use \r\n (not \n\r), which will
> produce the same result on whatever platform.
>
> Sources:
> 1. Following with-output-to-file docs shows that open-output-file
> http://docs.racket-lang.org/reference/file-ports.html?q=open-output-file%09#%28def._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._open-output-file%29%29
> 2. For background on escape sequences and behavior on Windows, one starting
> point is here:
> https://en.wikipedia.org/wiki/Escape_sequences_in_C#Table_of_escape_sequences
> For the equivalent of the behavior above, see docs for fopen on Windows, in
> particular text and binary modes.
>
> Cheers,
> Paolo
Paolo,
Thanks for the information. It seems that the Android App handles a plain '\n'
newline just fine. It's only when I read the file in Notepad that things get
strange.
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