Hi,  I am not able to create table or hash-table in r5rs. (define tbl (make-hash-table))  Its giving error "unbound identifier in module".  In the help also i am unable to find it.  Can you please tell me how to do this. Or there is  way to access mzscheme library in r5rs.  Also how to  access all documentation for r5rs, since  i am using this as module lang.   Thanks and Regards Vinay sachdev <div class="gmail_quote">On Sat, Jan 17, 2009 at 7:39 AM, Jens Axel Soegaard <<a href="mailto:jensaxel@soegaard.net">jensaxel@soegaard.net</a>> wrote: <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">Vinay Sachdev skrev:<div class="Ih2E3d"> <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> Hi,  I am reading SICP and i am at the start of chap-3.  I am using PLT-Scheme ver-4.0 .I ran into problem with  mutable pairs. it was giving error. So instead of using  set-car! i used set-mcar!, but then even to create list  i have to create mutable list.  I have an older version also(ver-3.71). Is it a bad idea to  install older version or is there any other way out? </blockquote> </div> In the module language, try this: #lang r5rs (let ((p (cons 1 2)))  (set-car! p 4)  (display p)) It prints (4 . 2).<div class="Ih2E3d"> <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">  My main purpose is to do read SICP and do its exercise.  One more question, is there any other issues with  PLT-Scheme in later chapters of SICP? </blockquote> </div> When you come to the picture language, use this PLaneT package: <a href="http://planet.plt-scheme.org/package-source/soegaard/sicp.plt/2/1/planet-docs/sicp-manual/index.html" target="_blank">http://planet.plt-scheme.org/package-source/soegaard/sicp.plt/2/1/planet-docs/sicp-manual/index.html</a> /Jens Axel </blockquote></div> -- Thanks and Regards Vinay Sachdev