Re: [slang-users] Newbie question

["John E. Davis" <davis@xxxxxxxxxxxxx>]

TJ Walls <twalls@xxxxxxxxxxxxxxxxxxxxxxx> wrote:

>   variable
>     article = article_as_string(),
>     % TJ: Ok, article_as_string returns a String_Type ...
>     i = is_substr (article, "\n\n"),

   Here, i represents the offset into article at the first occurance
   of "\n\n".  It is a "one-based" offset.

[...]
>	header = article[[0:i-1]];
>	% TJ: Here the problems start ... [0:i-1] is an array with
>	% TJ: elements initialized from 0 to (i-1), ok but 
>        % TJ: article is a String_Type what does article[array] mean?

   It is also a String_Type.  For example, if  
   
       article = "abcdefg";
       
   then article[[0,2,4,6]] represents the string "aceg";  So, in your
   example, since i represents the location of "\n\n", article[[0:i-1]]
   represents the string formed by the preceeding characters of article.

>	% TJ: Is it the first i members of the string ... it would seem
>	% TJ: we want the first i lines, but why does this work?
>	body = article[[i:]];
>     }   
>   
>   % remove continuation lines from the header
>   while (str_replace (header, "\n ", " "))
>     % TJ: Ok, replace the first newline character with a single
>     % TJ: whitespace ...
>     header = ();
>     % TJ: What does this mean!?

   Unfortunately, the str_replace function was poorly conceived on my
   part.  It has been made obsolete by the strreplace function.
   Instead of using

     while (str_replace (header, "\n ", " "))
       header = ();

   use:
   
      (header,) = strreplace (header, "\n ", " ", strlen (header));

   Here, strreplace returns 2 values: the modified string and an
   integer that indicates how many replacements were made.  In
   contrast, the str_replace function returns the modified string only
   if a replacement has been made.  This is what the "header=()"
   statement is all about.  I strongly urge you too read
   
      http://www.jedsoft.org/slang/doc/html/slang-9.html#ss9.5
      
   for more infomation about such constructs.

>   while (str_replace (header, "\n\t", " "))
>     header = ();
>   
>   % convert the header to an array of strings
>   header = strtok (header, "\n");
>   % TJ: Didn't we just replace all the newline characters??

   No, you replaced the combinations "\n " and "\n\t", but not "\n".

>   % do the actual sorting
>   sortres = array_sort (header, cmp);
>   header = header[sortres];
>   % TJ: header was a String_Type ... now it seems to be an array
>   % TJ: of strings??

   Right.  The strtok function returns an array of strings.  So after
   
      header = strtok (header, "\n");
      
   header is an array.

>  Thanks in advance for any advice for a newbie. Is there further
>documentation on S-lang beyond http://www.s-lang.org so that I might not 
>bother you with such silly questions in the future?
>
>  Also, does anyone know of a S-Lang editing mode for XEmacs?

Good luck.
--John

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