<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META content="text/html; charset=us-ascii" http-equiv=Content-Type> <META name=GENERATOR content="MSHTML 11.00.9600.16476"></HEAD> <BODY> <DIV dir=ltr align=left><FONT color=#0000ff size=2 face="Courier New"><SPAN class=494084909-28012014>Thanks.</SPAN></FONT></DIV> <DIV dir=ltr align=left><FONT color=#0000ff size=2 face="Courier New"><SPAN class=494084909-28012014>After your reassurance I found out what I did wrong in my code. I was confused by the fact that in my code will-try-execute always returned #f, but that was due to the following error: I registered the weak boxes in stead of the contents of these boxes. </SPAN></FONT><FONT color=#0000ff size=2 face="Courier New"><SPAN class=494084909-28012014></SPAN></FONT></DIV><BR> <BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #0000ff 2px solid; MARGIN-RIGHT: 0px" dir=ltr> <DIV lang=en-us class=OutlookMessageHeader dir=ltr align=left> <HR tabIndex=-1> <FONT size=2 face=Tahoma><B>From:</B> Carl Eastlund [mailto:carl.eastlund@gmail.com] <BR><B>Sent:</B> martes, 28 de enero de 2014 1:28<BR><B>To:</B> Jos Koot<BR><B>Cc:</B> Racket Users<BR><B>Subject:</B> Re: [racket] FW: weakly held symbols?<BR></FONT><BR></DIV> <DIV></DIV> <DIV dir=ltr> <DIV> <DIV>This isn't a typo. The docs are talking about the properties of the symbol tables for interned and unreadable symbols. There is no symbol table for uninterned symbols, so it wouldn't mean anything to talk about it.<BR><BR></DIV>Here's what this means for an interned symbol: you can create one, and while a reference to it exists, it stays in the symbol table. Any time you intern the same string, you'll get back that symbol. However, if all references to that symbol vanish, the symbol table is free to release that symbol. If anyone interns the same string again later, a new symbol will be created. For nearly all purposes, this is completely transparent, because you couldn't possibly have a copy of the old symbol to compare. There's almost no way to tell that the symbol you got before and the one you got after were different. The only way you'd ever know would be either by tracking memory use statistics, or by comparing the results of something like eq-hash-code, neither of which should be surprising to find out behaves impurely.<BR></DIV></DIV> <DIV class=gmail_extra><BR clear=all> <DIV>Carl Eastlund</DIV><BR><BR> <DIV class=gmail_quote>On Mon, Jan 27, 2014 at 5:53 PM, Jos Koot <SPAN dir=ltr><<A href="mailto:jos.koot@gmail.com" target=_blank>jos.koot@gmail.com</A>></SPAN> wrote:<BR> <BLOCKQUOTE class=gmail_quote style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid"><U></U> <DIV> <DIV dir=ltr align=left><FONT color=#0000ff face="Courier New"><SPAN>It appears that my previous email was not sent completely. Sorry for that. Here is the complete question.</SPAN></FONT></DIV> <DIV dir=ltr align=left><FONT color=#0000ff face="Courier New"><SPAN></SPAN></FONT> </DIV> <DIV dir=ltr align=left><SPAN> <DIV class=im> <DIV><FONT color=#0000ff face="Courier New"><SPAN>Hi to all,</SPAN></FONT></DIV> <DIV><FONT color=#0000ff face="Courier New"><SPAN></SPAN></FONT> </DIV> <DIV><FONT color=#0000ff face="Courier New"><SPAN>Section "3.6 symbols" of the Racket reference manual states:</SPAN></FONT></DIV> <DIV><FONT color=#0000ff face="Courier New"><SPAN></SPAN></FONT> </DIV></DIV> <DIV><SPAN><FONT face="Courier New"><FONT color=#0000ff><FONT size=+0>Interned and unreadable symbols are only weakly held ... but a symbol maay disappear when ... used as the key in a weak hash table ..."<SPAN>.</SPAN></FONT></FONT></FONT></SPAN></DIV> <DIV><SPAN><FONT face="Courier New"><FONT color=#0000ff><FONT size=+0><SPAN></SPAN></FONT></FONT></FONT></SPAN> </DIV> <DIV><SPAN><FONT face="Courier New"><FONT color=#0000ff><FONT size=+0><SPAN>I would understand:</SPAN></FONT></FONT></FONT></SPAN></DIV> <DIV><SPAN><FONT face="Courier New"><FONT color=#0000ff><FONT size=+0><SPAN></SPAN></FONT></FONT></FONT></SPAN> </DIV> <DIV><SPAN><FONT face="Courier New"><FONT color=#0000ff><FONT size=+0><SPAN><SPAN><FONT face="Courier New"><FONT color=#0000ff><FONT size=+0>UNINTERNED and unreadable symbols are only weakly held ... but a symbol may disappear when ... used as the key in a weak hash table ..."<SPAN>.</SPAN></FONT></FONT></FONT></SPAN></SPAN></FONT></FONT></FONT></SPAN></DIV> <DIV><SPAN><FONT face="Courier New"><FONT color=#0000ff><FONT size=+0><SPAN><SPAN><FONT face="Courier New"><FONT color=#0000ff><FONT size=+0><SPAN></SPAN></FONT></FONT></FONT></SPAN></SPAN></FONT></FONT></FONT></SPAN> </DIV> <DIV><SPAN><FONT face="Courier New"><FONT color=#0000ff><FONT size=+0><SPAN><SPAN><FONT face="Courier New"><FONT color=#0000ff><FONT size=+0><SPAN>May be just a typo, but as I am not sure I understand the docs well, I post my question here instead of posting a bug report.</SPAN></FONT></FONT></FONT></SPAN></SPAN></FONT></FONT></FONT></SPAN></DIV> <DIV><SPAN><FONT face="Courier New"><FONT color=#0000ff><FONT size=+0><SPAN><SPAN><FONT face="Courier New"><FONT color=#0000ff><FONT size=+0><SPAN></SPAN></FONT></FONT></FONT></SPAN></SPAN></FONT></FONT></FONT></SPAN> </DIV> <DIV><SPAN><FONT face="Courier New"><FONT color=#0000ff><FONT size=+0><SPAN><SPAN><FONT face="Courier New"><FONT color=#0000ff><FONT size=+0><SPAN>Greetings, Jos</SPAN></FONT></FONT></FONT></SPAN></SPAN></FONT></FONT></FONT></SPAN></DIV></SPAN></DIV></DIV><BR>____________________<BR> Racket Users list:<BR> <A href="http://lists.racket-lang.org/users" target=_blank>http://lists.racket-lang.org/users</A><BR><BR></BLOCKQUOTE></DIV><BR></DIV></BLOCKQUOTE></BODY></HTML>