<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; charset=iso-8859-1"> <META content="MSHTML 6.00.6000.16608" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#ffffff> <DIV><FONT face=Arial size=2>Download my PLT implementation of Phil Bewig's SRFI-41 form the following link.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2> <DIV><FONT face=Arial size=2><A href="http://www.telefonica.net/web2/koot/zipped-streams.zip">http://www.telefonica.net/web2/koot/zipped-streams.zip</A></FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV>At Phil's request, the code has been modified as little as possible.</FONT></DIV> <DIV><FONT face=Arial size=2>The included tests, leak tests included, run well on DrScheme, version 3.99.0.12-svn14feb2008 [3m].</FONT></DIV> <DIV><FONT face=Arial size=2>Documentation is included in msword (doc) and html format (without having been touched by me) </FONT></DIV> <DIV><FONT face=Arial size=2>Docs have not yet been scribled (I am not much of a scribbler, I'm afraid)</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>Especially for Matthew Flatt:</FONT></DIV> <DIV><FONT face=Arial size=2>Thanks for fixing <FONT face="Times New Roman" size=3> </FONT><A href="http://bugs.plt-scheme.org/query/?cmd=view&pr=8963" target=_blank><FONT face="Times New Roman" size=3>http://bugs.plt-scheme.org/query/?cmd=view&pr=8963</FONT></A>.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>Especially for Eli Barzilay</FONT></DIV> <DIV><FONT face=Arial size=2>Initially I thought native PLT promises could be used.</FONT></DIV> <DIV><FONT face=Arial size=2>Nevertheless the code includes its own code for van Tonder promises (SRFI 45)</FONT></DIV> <DIV><FONT face=Arial size=2>For two reasons:</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>1:    there is still a problem with the van Tonder promises as now implemented in PLT Scheme.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>2:    streams must be a distinct type, for they must not be confused with promises as delivered by syntaxes delay and lazy.</FONT></DIV> <DIV><FONT face=Arial size=2>Otherwise we would get in trouble with something like: </FONT><FONT face=Arial size=2>(stream 1 (delay 1) (lazy (delay 1)))</FONT></DIV> <DIV><FONT face=Arial size=2>There is no such thing as 'make-promise-type'.</FONT></DIV> <DIV><FONT face=Arial size=2>An alternative would be to wrap PLT's promises in a struct-type, but I find this extra layer not attractive.</FONT></DIV> <DIV><FONT face=Arial size=2>As they are now, the streams are already slow enough.</FONT></DIV> <DIV><FONT face=Arial size=2>The implementation of the van Tonder promises is as simple as possible (in fact copied from SRFI 45)</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>I suggested to Phil Bewig several ways of improving the performance, some of which he copied.</FONT></DIV> <DIV><FONT face=Arial size=2>However, with respect to many other suggestions Phil Bewig asked me with some force to keep as close to his code as possible. So I did.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>When PLT R6RS arrives, it will be little work to adapt the code or may be just copy the R6RS version as already prepared by Phil Bewig.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>Of course I am available in case of problems, bugs, questions, and so on.</FONT></DIV> <DIV><FONT face=Arial size=2>I am sure the same holds for Phil Bewig.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>Kind regards,</FONT></DIV> <DIV><FONT face=Arial size=2>Jos Koot</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>(define-syntax expose-stream-lazy (syntax-rules ( ) ((_ expr) ((stream-lambda ( ) expr)))))  ;)</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2></FONT> </DIV></BODY></HTML>