[plt-scheme] Re: PLT R6RS questions and answers

From: Tom Gordon (thomas.gordon at fokus.fraunhofer.de)
Date: Tue Nov 25 05:01:06 EST 2008

On Nov 24, 2008, at 5:41 PM, Matthias Felleisen wrote:

>> PLT's support for R6RS seems somewhat half-hearted and ambiguous.
> Tom, I reject this as unfair. Compare our implementation to those of  
> others, and we are ahead still. Matthew provides test suits for R6RS  
> and friends, which others borrow to develop their own R6RS  
> implementations. Why should we do more than those people? But  
> perhaps you're really requesting that PLT stay away from RnRS  
> efforts. -- Matthias

Dear Matthias,

I'm sorry you feel this way.  I'm trying to be fair and have already  
said that I think I understand your dilemma, as researchers, between  
wanting both to support standards like R6RS while at the same time  
being innovative and pushing the envelope.

I appreciate your work and do not feel it is my place to suggest what  
your priorities should be.  I can try to give you, as a PLT user, some  
constructive feedback and let you know more about our requirements and  

I don't know what people you are talking about, who you claim are  
doing less than the PLT team to support R6RS.  For my part, and my  
colleagues, we took the effort to port our entire system to from PLT  
Scheme to R6RS.   This involved porting, or helping to port, a number  
of SRFIs, the SSAX and SXML libraries, the PSTK (Tcl/TK graphics  
library) and some other stuff to R6RS and make this code available to  
others <http://carneades.berlios.de>.   The lack of sufficient  
interoperability between PLT modules and R6RS libraries, in particular  
the problem with immutable PLT lists, made it necessary for us to port  
libraries, such as the SSAX library, which are already available for  
PLT.  (But I do not want to complain about this, because it gave us  
the incentive to begin porting the libraries we need to R6RS.)

Is the PLT Team planning to port any of its modules to R6RS libraries,  
or find a way to compile PLT modules to R6RS libraries?  Are you  
planning to use R6RS when developing new libraries?   In other words,  
does the PLT Team intend to participate in the effort to create a  
large collection of freely available and portable R6RS libraries,  
which would benefit the larger community of all R6RS users, and not  
just the PLT Scheme community?

I do not feel you have any obligation or commitment to take part in  
this effort.   I just would be grateful if you would share your vision  
and plans with us.   I guess we all want Scheme to succeed.  And there  
may be various paths to success.  One model is the one taken by the  
Python and Perl communities:  one implementation (more or less) the  
most recent version of which always serves as the de facto standard.  
Another model is based on an open, evolving standard, such as the RnRS  
series, with lots of different implementations.   I had thought PLT  
was commited to working with other Scheme implementators on this  
second approach.  But now I'm not so sure.



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