September 2012

After watching Bret Victor’s Inventing on Principle, I just had to figure out a way of getting live reloading to work. I know about LiveReload, of course, and everything I’ve heard about it is good. But their Windows version is in alpha, and I’m not about to experiment just yet. This little script does it for me instead: (function(interval, location) { var lastdate = ""; function updateIfChanged() { var req = new XMLHttpRequest(); req.open("HEAD", location.href, false); req.send(null); var date = req.getResponseHeader("Last-Modified"); if (!lastdate) { lastdate = date; } else if (lastdate != date) { location.reload(); } } setInterval(updateIfChanged, interval); })(300, window.location); It checks the current page every 300 milliseconds and reloads it if the Last-Modified header is changed. I usually include it as a minified script: ...

Here’s the easiest way to set up a Windows XP virtual machine that I could find. (This is useful if you want to try out programs without installing it on your main machine; test your code on a new machine; or test your website on IE6 / IE7 / IE8.) Go to the Virtual PC download site. (I tried VirtualBox and VMWare Player. Virtual PC is better if you’re running Windows on Windows.) If you have Windows 7 Starter or Home, select “Don’t need XP Mode and want VPC only? Download Windows Virtual PC without Windows XP Mode.” If you have Windows Vista or Windows 7, select “Looking for Virtual PC 2007?” Download it. (You may have to jump through a few hoops like activation.) Download Windows XP and run it to extract the files. (It’s a 400MB download.) Open the “Windows XP.vmc” file – just double-clicking ought to work. At this point, you have a working Windows XP version. (The Administrator password is “Password1”.) Under Tools – Settings – Networking – Adapter 1, select “Shared Networking (NAT)” That’s pretty much it. You’ve got a Windows XP machine running inside your other Windows machine. ...

Lisp users would laugh, since they have macros, but Python supports some basic code inspection and modification. Consider the following pieces of code: margin = lambda v: 1 - v['cost'] / v['sales'] What if you wanted another function that lists all the dictionary indices used in the function? That is, you wanted to extract cost and sales? This is a real-life problem I encountered this morning. I have 100 functions, each defining a metric. For example, ...