[twg-tds] [gaulle@idris.fr: a TDS question]

[Walter Schmidt]

On Mon, 30 Jun 2003 02:26:10 +0200, Reinhard Kotucha wrote:

>The TDS is a standard which does not depend on a specific
>implementation.  

The TDS document says:

"As a result, the TWG concluded that a comprehensive TDS
requires implementations to support some form of implicit 
subdirectory  searching.
More precisely, implementations must make it possible to
specify that TeX, METAFONT and their companion utilities 
search in both a specified directory and recursively through 
all subdirectories of that directory when looking for an input 
file."

>Regarding web2c as a reference implementation, I
>think that we can assume that if something works with web2c, it can be
>implemented on any TDS compliant system.

At first sight this seems to be  correct, but...

>If you say 
>   /input <dir>/<file>

You mean, for instance:

  \input base/article.cls 

The TDS document does not clearly specify how this case 
(i.e., searching for a given _directory_ name) is to be handled.  
It seems "natural" to me, that specifying a directory implies
that the location of the file is already known, and TeX needs 
NOT to perform recursive searching.

>kpathsea searches for <file> according to the rules in texmf.cnf
>(nothing has to be changed here) and returns the first file that is in
>a subdirectory <dir>.

This does not work with VTeX/Free and emTeX.  When a directory 
is specified, then the file is found _only_ in this directory 
(relative to the current one, if it's a relative path), but not 
along the normal search path.

> LaTeX is designed to work
>with file systems that do not know what a subdirectory is at well.
>That means that it depends on unique filenames.

ACK

>[...] if you write a
>LaTeX package that makes assumptions about the file system you
>probably break some (commercial) non-TDS based TeX systems.

As you can see above, you even break TDS-compliant systems.

best wishes
Walter