set-cdr! and set-car! were banished to their own library. From what I understand, immutable pairs are the new default. Mutable pairs can still be created using such functions as mcons and mcar, and can be modified using the new set-mcar! and set-mcdr! For more information, look here: "Getting rid of set-car! and set-cdr!" <a href="http://blog.plt-scheme.org/2007/11/getting-rid-of-set-car-and-set-cdr.html" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">http://blog.plt-scheme.org/2007/11/getting-rid-of-set-car-and-set-cdr.html</a> <div>On 8/9/08, LordGeoffrey <<a href="mailto:lordgeoffrey@optushome.com.au" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">lordgeoffrey@optushome.com.au</a>> wrote:<blockquote class="gmail_quote" style="margin-top: 0; margin-right: 0; margin-bottom: 0; margin-left: 0; margin-left: 0.80ex; border-left-color: #cccccc; border-left-width: 1px; border-left-style: solid; padding-left: 1ex"> Hi, Is this something wrong with my drscheme configuration (which i always find confusing) or incompatibilities with v4 Settings: Language: Pretty Big (includes MrEd and Advanced Student); memory limit: 128 megabytes. Used: (require (planet "csv.ss" ("neil" "csv.plt" 1 1))) Thanks _________________________________________________  For list-related administrative tasks:  <a href="http://list.cs.brown.edu/mailman/listinfo/plt-scheme" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">http://list.cs.brown.edu/mailman/listinfo/plt-scheme</a> </blockquote></div>