Cracking The Credit Card Code | MintLife Blog | Personal Finance News & Advice

This is probably the best presentation I have seen explaining how check digit routines work. We use these at work for non-credit card numbers, and usually you have to suffer through them once. If you are smart and you write proper object oriented code, you'll be able to reuse your check digit for say, Generic Airlines Frequent Flyer, as many times as you want since once they adopt the scheme odds are they'll stick for it for years.

When this turns challenging is when the spec documents are sloppy. I implemented one of these check digits for a customer in the hospitality industry, and their example case for the check digit routine had a tiny little redundancy error. The result? My check digit routine was WRONG, but it WORKED with the example account numbers. Fun times ...

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On sleep deprivation and Incan Monkey Gods

From: Dilbert comic strip for 08/03/1992 from the official Dilbert comic strips archive. I was trying to show this strip to a coworker who is dangerously toying with the harsh mistress that is Insomnia. What shocked me is how quickly I was able to look up the strip, which was published when he was just 11 years old, and two weeks before my just-out-of-college ass shipped out to US Army Basic Training.

The Black Hole

If this was a minigolf hole, you can't reach B from A. Ever. If this was a room lined with mirrors, and you lit a candle at point A, you can't see it from B, not even reflected. Update: I guess I didn't explain this all the way through. You can't reach B from A with just one stroke, there's no direct line between them, and there is no way to bounce the ball (assuming perfect conditions). Thanks to Ben for pointing this obvious error.

Goodbye Blackberry 8530, hello Samsung Intercept (both Virgin Mobile USA)

Got the phone switching bug again, and this time I am going to try to see if I can live with an Android phone . According to Virgin Mobile, they will be upgrading their Samsung Intercept to 2.2 froyo sometime in Spring, since I am completely new to Android I am not too worried about it yet. And no, I am not interested in a jailbreak. The dots are used for the unlock pattern, which after very little time becomes instinctive, much easier than having to remember a password. The new phone is slightly longer and narrower than my Blackberry 8530. The back cover is as flimsy. The Samsung Intercept is of course thicker since it has a slide-out keyboard. I haven't measured them, but the new keyboard feels at least twice as wide as the one in the Blackberry. The only problem is that due to the USB port being on the top of the phone, and I am a lefty, it is really damn hard for me to type if I am charging the phone. I imagine right handed people have the same ki...

The Insomniac Coder

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