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patrickwonders
patrickwonders

Ebay Jeebies (take three...)

Brief timeline:

  • Saturday at 8:00pm-ish: Bid on laptop.
  • Sunday at 10:00am-ish: See I won the auction.
  • Sunday just after that: Pay $2050.00 on a Discover card via PayPal
  • Sunday afternoon-ish: Start poking around at seller's identity.
  • Monday all day-ish: Start freaking out that there is no laptop and dreading having to jump through hoops to get PayPal/EBay to refund me.
  • Tuesday at 2:00am-ish: EBay pulls the auction and PayPal launches an investigation.
  • Tuesday at 3:00pm-ish: I email PayPal asking what sort of timeframe I should expect.
  • Wednesday at 9:00am-ish: PayPal tells me they try to resolve everything in less than 30 days, but some things take longer.
  • Wednesday at 4:00pm-ish: PayPal closes investigation and reverses the charges.

So, I'm all back to even. Go EBay and PayPal! Yay!


patrickwonders
patrickwonders

Things look nice in lisp...

So, very often for things that I'm toying with, I want to have a polynomial that meets certain criteria. For most applications in the past, I have sat down and figured it all out by hand.

Today, I was having trouble getting the conditions that I wanted specified enough to get the sort of polynomial that I was expecting. After finding the coefficients for several sixth degree polynomials in a row, I figured I should instead be able to do something like this with the proper lisp:

(calculate-polynomial-subject-to (value :at 0 :equals 0) (derivative :at 0 :equals 0) (nth-derivative 2 :at 0 :equals 0) (value :at 1 :equals 1) (derivative :at 1 :equals 0) (nth-derivative 2 :at 1 :equals 0) (value :at 1/2 :equals 3/4))

That's all done now. So, for the record, the above is:

26x3 - 63x4 + 54x5 - 16x6

Which is still not quite what I'm looking for for this application, but it's close.

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