<HTML><BODY style="word-wrap: break-word; -khtml-nbsp-mode: space; -khtml-line-break: after-white-space; ">Thanks - I thought this continuations stuff was pretty interesting. <DIV><BR class="khtml-block-placeholder"></DIV><DIV>Struck me that some sort of journaling of object changes might be a good way of rewinding to previous states arbitrarily. You'd have to redefine some pretty low-level stuff, but then once it's done the higher level code gets much simpler:</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>Object.checkpoint(:some_point)</DIV><DIV># do stuff</DIV><DIV>Object.rewind_to(:some_point)</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>Needs refining to make it work across the whole program state ... any ideas?</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>Chris ('crap rails code' guy :-)</DIV><DIV><DIV><BR><DIV><DIV>On 12 Mar 2007, at 22:05, Marcus Roberts wrote:</DIV><BR class="Apple-interchange-newline"><BLOCKQUOTE type="cite"><BR><DIV><DIV>If people are interested in the <FONT class="Apple-style-span" face="Times" size="3"><SPAN class="Apple-style-span" style="font-size: 13px;">Structure and Interpretation of Computer Programs book mentioned at tonight's meeting<FONT class="Apple-style-span" face="Helvetica" size="3"><SPAN class="Apple-style-span" style="font-size: 12px;">,</SPAN></FONT></SPAN></FONT> it's available online here:</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV><A href="http://mitpress.mit.edu/sicp/">http://mitpress.mit.edu/sicp/</A></DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV><BR class="khtml-block-placeholder"></DIV></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">_______________________________________________</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">chat mailing list</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><A href="mailto:chat@lrug.org">chat@lrug.org</A></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><A href="http://lists.lrug.org/listinfo.cgi/chat-lrug.org">http://lists.lrug.org/listinfo.cgi/chat-lrug.org</A></DIV> </BLOCKQUOTE></DIV><BR></DIV></DIV><BR><BR><DIV> <SPAN class="Apple-style-span" style="border-collapse: separate; border-spacing: 0px 0px; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: auto; -khtml-text-decorations-in-effect: none; text-indent: 0px; -apple-text-size-adjust: auto; text-transform: none; 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