<HTML><BODY style="word-wrap: break-word; -khtml-nbsp-mode: space; -khtml-line-break: after-white-space; ">Thanks for the detailed reply, John. Let me answer some of your questions and ask some more of mine. <DIV><BR class="khtml-block-placeholder"><DIV><BLOCKQUOTE type="cite"><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">For a start, what operations do you want to perform on this "bit vector"?</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><BR></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Let's assume at the very least it should have get/set like a list, but contained objects are restrained to belong to set([0, 1]).</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><BR></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Maybe it should also support something like this:</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><BR></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">three = Bitvector([1, 1,])</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">six = Bitvector([ 0, 1, 1])</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">seven = Bitvector([1, 1, 1])</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">two = Bitvector([0, 1])</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">assert three | six == seven</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">assert three & six == two</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><BR></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Which operations are required only inside the extension, and which operations need to be exposed to the user of the extension?</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><BR></DIV></BLOCKQUOTE><DIV><BR class="khtml-block-placeholder"></DIV><DIV>The only operations I need are setting bits, getting the bits that are not set etc. Nothing too fancy. I am probably going to be the only user of this extension as this is research code for now. </DIV><DIV><BR class="khtml-block-placeholder"></DIV><BLOCKQUOTE type="cite"><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">"grow" and "needed" are a little contradictory. Do you want an *exact* size, so that you can do this:</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><BR></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">zero = Bitvector(size=20, contents=[0])</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">all_ones = ~zero</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><BR></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">and know exactly how long the result will be?</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><BR></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">What makes you think a long int would grow unconscionably longer than needed? How long is your longest map going to be? In any case, just think int, which morphs seamlessly into long as and when required. A 20-bit map would fit into an int.</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><BR></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Another thing to worth contemplating: given the amount of going-over by Tim Peters that the long int code has had, if long ints waste more memory on leading zeroes than n bits [where n is < 32 and could be determined by inspecting the code], then the end of the world is nigh.</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><BR></DIV></BLOCKQUOTE><DIV><BR class="khtml-block-placeholder"></DIV><DIV>My bit-vector sizes can vary from 10-bits to 60-bits with an average length of around 25-30 bits. So, would a long int be the best way then ? I was just worried that I would be wasting too much memory. </DIV><BR><BLOCKQUOTE type="cite"><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">"This" wouldn't be doing the storing. *You* would be [mis]using a byte array as a bit array.</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><BR></DIV></BLOCKQUOTE><DIV><BR class="khtml-block-placeholder"></DIV><DIV>Hmm. So, is there a correct way to use array.array for bit vectors?</DIV><DIV><BR class="khtml-block-placeholder"></DIV><BLOCKQUOTE type="cite"><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">*Every* type necessarily has more than one bit of baggage. [Sorry; the cheer squad was hollerin' "Pun! Pun! Pun!"]</DIV></BLOCKQUOTE><DIV><BR class="khtml-block-placeholder"></DIV><DIV>I guess I deserved that :)</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>Thanks again !</DIV><DIV>Nitin</DIV></DIV><DIV><FONT class="Apple-style-span" color="#0000DD"></FONT></DIV></DIV></BODY></HTML>