More of my thoughts have been stolen: In my
previous job the customer wanted a progress bar displayed while information was copied off of proprietary hardware, during which the software didn't get any indication of progress until the copy
was finished. I joked (mostly) that we could display a progress bar that continuously slows down and never quite reaches the end until we know we're done getting info from the hardware. The amount
of progress would be a function of time where as time approaches infinity, progress approaches a value of at most 100 percent.
This is similar to Zeno's Paradox which says you can't cross a room because to do so first you must cross half the room, then you must cross half the remaining distance, then half the remaining again, and so on which means you must take an infinite number of steps. There's also an old joke inspired by Zeno's Paradox. The joke is the prototypical engineering vs sciences joke and is moderately humorous, but I think the fact that Wolfram has an interactive applet demonstrating the joke is funnier than the joke itself.
I recently found Lou Franco's blog post "Using Zeno's Paradox For Progress Bars" which covers the same concept as Zeno's Progress Bar but with real code. Apparently Lou wasn't making a joke and actually used this progress bar in an application. A progress bar that doesn't accurately represent progress seems dishonest. In cases like the Vista Defrag where the software can't make a reasonable guess about how long a process will take the software shouldn't display a progress bar.
Similarly a paper by Chris Harrison "Rethinking the Progress Bar" suggests that if a progress bar speeds up towards the end the user will perceive the operation as taking less time. The paper is interesting, but as in the previous case, I'd rather have progress accurately represented even if it means the user doesn't perceive the operation as being as fast.
Update: I should be clearer about Lou's post. He was actually making a practical and implementable suggestion as to how to handle the case of displaying progress when you have some idea of how long it will take but no indications of progress, whereas my suggestion is impractical and more of a joke concerning displaying progress with no indication of progress nor a general idea of how long it will take.
This post is about creating a server side z-code
interpreter that represents game progress in the URI. Try it with the game Lost
Pig.
I enjoy working on URIs and have the mug to prove it. Along those lines I've combined thoughts on URIs with interactive fiction. I have a limited amount of experience with Inform which generates Z-Code so I'll focus on pieces written in that. Of course we can already have URIs identifying the Z-Code files themselves, but I want URIs to identify my place in a piece of interactive fiction. The proper way to do this would be to give Z-Code its own mimetype and associate with that mimetype the format of a fragment that would contain the save state of user's interactive fiction session. A user would install a browser plugin that would generate URIs containing the appropriate fragment while you play the IF piece and be able to load URIs identifying Z-Code files and load the save state that appears in the fragment.
But all of that would be a lot of work, so I made a server side version that approximates this. On the Web Frotz Interpreter page, enter the URI of a Z-Code file to start a game. Enter your commands into the input text box at the bottom and you get a new URI after every command. For example, here's the beginning of Zork. I'm running a slightly modified version of the Unix version of Frotz. Baf's Guide to the IF Archive has lists of IF games to try out.
There are two issues with this thought, the first being the security issues with running arbitrary z-code and the second is the practical URI length limit of about 2K in IE. From the Z-Code standard and the Frotz source it looks like 'save' and 'restore' are the only commands that could do anything interesting outside of the Z-Code virtual machine. As for the length-limit on URIs I'm not sure that much can be done about that. I'm using a base64 encoded copy of the compressed input stream in the URI now. Switching to the actual save state might be smaller after enough user input.
IPv6 address syntax consists of 8 groupings of colon delimited 16-bit hex values making up the 128-bit address. An optional double colon
can replace any consecutive sequence of 0 valued hex values. For example the following is a valid IPv6 address: fe80::2c02:db79
Some IPv6 addresses aren't global and in those cases need a scope ID to describe their context. These get a '%' followed by the scope ID.
For example the previous example with a scope ID of '8' would be: fe80::2c02:db79%8
IPv6 addresses in URIs may appear in the host section of a URI as long as they're enclosed by square brackets. For example:
http://[fe80::2c02:db79]/. The RFC explicitly notes that there isn't a way to add a scope ID to the IPv6 address in a URI. However a draft document describes adding
scope IDs to IPv6 addresses in URIs. The draft document uses the IPvFuture production from the URI RFC with a 'v1' to add a new
hostname syntax and a '+' instead of a '%' for delimiting the scope id. For example: http://[v1.fe80::2c02:db79+8]/. However, this is still a draft document, not a final
standard, and I don't know of any system that works this way.
In Windows XPSP2 the IPv6 stack is available but disabled by default. To enable the IPv6 stack, at a command prompt run 'netsh interface ipv6 install'. In Vista IPv6 is the on by default and cannot be turned off, while the IPv4 stack is optional and may be turned off by a command similar to the previous.
Once you have IPv6 on in your OS you can turn on IPv6 for IIS6 or just use IIS7. The address ::1 refers to the local machine.
In some places in Windows like UNC paths, IPv6 addresses aren't allowed. In those cases you can use a Vista DNS IPv6 hack that lives in the OS
name resolution stack that transforms particularly crafted names into IPv6 addresses. Take your IPv6 address, replace the ':'s with '-'s and the '%' with an 's' and then append '.ipv6-literal.net'
to the end. For example: fe80--2c02-db79s8.ipv6-literal.net. That name will resolve to the same example I've been using in Vista. This transformation occurs inside the system's local
name resolution stack so no DNS servers are involved, although Microsoft does own the ipv6-literal.net domain name.
MSDN describes IPv6 addresses in URIs in Windows and I've described IPv6 addresses in URIs in IE7. File URIs in
IE7 don't support IPv6 addresses. If you want to put a scope ID in a URI in IE7 you use a '%25' to delimit the scope ID and due to a bug you must have at least two digits in your scope ID. So,
to take the previous example: http://[fe80::2c02:db79%2508]/. Note that its 08 rather than just 8.
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