A friend showed me this puzzling code the other day.

Can you guess the output?

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[22:11:41 mburke]$ php -a
Interactive shell

php > class Test { };
php > $A = new Test();
php > var_dump($A);
object(Test)#1 (0) {
}

php > $B = new $A();
php > var_dump($B);

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$ alias please="sudo"
$ please apachectl restart
$ please make install
$ please rm -rf /

Mind your P’s and Q’s.

HT: Mohsen

HT: @AutomatedTester

Just learned RVM can automatically switch ruby versions based on the current directory.

No more trying to remember which magic rvm use incantation will return your project to a working state.

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I ran into trouble the other day running rspec on my project. It had been working just fine the day before, but all of a sudden:

/Users/mburke/.rvm/rubies/ruby-1.8.7-p302/lib/ruby/1.8/i686-darwin12.3.0/digest/sha1.bundle: dlopen(/Users/mburke/.rvm/rubies/ruby-1.8.7-p302/lib/ruby/1.8/i686-darwin12.3.0/digest/sha1.bundle, 9): Library not loaded: /opt/local/lib/libcrypto.1.0.0.dylib (LoadError) ..snip ..

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This is part II of a series looking at the physics algorithm for Electric Field Hockey. Part I outlines the initial algorithm and it’s shortcomings.

Last time we noticed a problem in how we generate a time step for our physics simulation: requestAnimationFrame can’t guarantee a consistent interval which makes the simulation appear frustratingly irrational.

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Never let your physics simulation depend on something as unreliable and capricious as the machine’s framerate.

When I was building Electric Field Hockey I used window.requestAnimationFrame to control the time-step for all the physics calculations.

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Simulation.prototype.tick = function(frame) {
	var ts = frame.timeDiff / 1000;
	var puck = this.puck;
	var force = puck.charge.calcForceFrom( this.charges );
	var newPosition = EFH.Physics.calcPosition(puck.charge,
				puck.velocity, force, ts);
	puck.velocity = EFH.Physics.calcVelocity(puck.velocity,
				force, ts);

	puck.moveTo(newPosition.x, newPosition.y);

};

var init = function() {
	/* SNIP */
	self.anim = new Kinetci.Animation(function(frame) {
		self.tick( frame );
	});
};

It’s easy and straight forward: every time the browser wanted a new frame, we can calculate the forces, apply them to the objects, and figure out the new positions.

But it’s also simplistic.

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LoadModule proxy_module modules/mod_proxy.so
LoadModule proxy_http_module modules/mod_proxy_http.so
ProxyRequests off
ProxyPass /s3/ http://s3.amazonaws.com/your_bucket/

Update: Add Cache-Control headers

I wanted to learn a little about ray tracing, and I’m kind of obsessed with javascript at the moment so i cranked out this little gem. I’m planning to add more features to it when I get a chance, but for now you can set the parameters for the sphere and location of the light source. Press ‘Trace’ to get an image on the canvas (which may take a few seconds).

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