[Rd] problem with \eqn (PR#8322)

[Kurt Hornik]

>>>>> Hin-Tak Leung writes:

> Ross Boylan wrote:
>> On Mon, 2005-11-21 at 10:27 +0000, Hin-Tak Leung wrote:
>> 
>>> Kurt Hornik wrote:
>>> <snipped>
>>> 
>>>> Definitely a problem in Rdconv.
>>>> 
>>>> E.g.,
>>>> 
>>>> $ cat foo.Rd 
>>>> \description{
>>>> \eqn{{A}}{B}
>>>> }
>>>> hornik at mithrandir:~/tmp$ R-d CMD Rdconv -t latex foo.Rd | grep eqn
>>>> \eqn{{A}}{A}{{B}
>>>> 
>>>> shows what is going on.
>>> 
>>> There is a "work-around" - putting extra spaces between the two braces:
>>> 
>>> $ cat foo.Rd
>>> \description{
>>> \eqn{ {A} }{B}
>>> }
>>> 
>>> $R CMD Rdconv -t latex foo.Rd
>>> \HeaderA{}{}{}
>>> \begin{Description}\relax
>>> \eqn{ {A} }{B}
>>> \end{Description}
>>> 
>>> 
>>> HT
>> 
>> Terrific!  I can confirm that works for me and, in a way, a work-around
>> is better than a fix.  With the work-around, I can distribute the
>> package without needing to require that people get some not-yet-release
>> version of R that fixes the problem.  I do hope the problem gets fixed
>> though :)
>> 
>> By the way, I  couldn't see how the perl code excerpted earlier paid any
>> attention to {}.  But perl is not my native tongue.
>> 
>> Ross
>> 

> Glad to hear - the extra space in the latex-eqn-processed part of
> \eqn (versus the ascii part) possibly get skipped so there shouldn't
> be visual difference if it works.

> Regarding the perl code - "share/perl/R/Rdconv.pm" around line 400 - 
> reproduced again here - the way I understand it, "\eqn{{a}}{b}" is first
> transformed into something like
> "\eqnbraces1brace2abrace2brace1brace1bbrace1", then called as
> "get_arguments {'eqn', ..., 2}", which then tries to extract "a" and 
> "b". $ID is defined elsewhere to be "brace1", etc. That's the idea.
> The 4 regular expressions - the 1st, 2nd and the 4th probably should be
> non-greedy (i.e. "??" instead of "?", and ".*?" instead of ".*"). But 
> then, this is just my idea and I haven't tried very hard to figure out
> what it is supposed and not supposed to do...

> For those who wants to get to the bottom of it, I think inserting
> something like this (this just append $text into a tmp file) would be 
> useful, against the small snipplet that Kurt provided:
>      open(JUNK, ">> /tmp/junk");
> 	print JUNK "outer/inner loop:", $text, "\n";
>      close(JUNK);

> HT

> =======================
> ## Get the arguments of a command.
> sub get_arguments {
>      my ($command, $text, $nargs) = @_;
>      ## Arguments of get_arguments:
>      ##  1, command: next occurence of 'command' is searched
>      ##  2, text:    'text' is the text containing the command
>      ##  3, nargs:   the optional number of arguments to be extracted;
>      ##              default 1
>      my @retval;
>      ## Returns a list with the id of the last closing bracket and the
>      ## arguments.

>      if($text =~ /\\($command)(\[[^\]]+\])?($ID)/){
>          $id = $3;
>          $text =~ /$id(.*)$id/s;
>          $retval[1] = $1;
>          my $k=2;
>          while(($k<=$nargs) && ($text =~ /$id($ID)/)){
>              $id = $1;
>              $text =~ /$id\s*(.*)$id/s;
>              $retval[$k++] = $1;
>          }
>      }
>      $retval[0] = $id;
>      @retval;
> }
> ==================

> HT

I think I have a fix for this.  Will shortly commit to r-devel.

-k