• 14 Posts
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Joined 1 year ago
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Cake day: June 14th, 2023

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  • A problem that only affects newbies huh?

    Let’s say that you are writing code intended to be deployed headless in the field, and it should not be allowed to exit in an uncontrolled fashion because there are communications that need to happen with hardware to safely shut them down. You’re making a autonomous robot or something.

    Using python for this task isn’t too out of left field, because one of the major languages of ROS is python, and it’s the most common one.

    Which of the following python standard library functions can throw, and what do they throw?

    bytes, hasattr, len, super, zip



  • Oh, I’ll try to describe Euler’s formula in a way that is intuitive, and maybe you could have come up with it too.

    So one way to think about complex numbers, and perhaps an intuitive one, is as a generalization of “positiveness” and “negativeness” from a binary to a continuous thing. Notice that if we multiply -1 with -1 we get 1, so we might think that maybe we don’t have a straight line of positiveness and negativeness, but perhaps it is periodic in some manner.

    We can envision that perhaps the imaginary unit, i, is “halfway between” positive and negative, because if we think about what √(-1) could possibly be, the only thing that makes sense is it’s some form of 1 where you have to use it twice to make something negative instead of just once. Then it stands to reason that √i is “halfway between” i and 1 in this scale of positive and negative.

    If we figure out what number √i we get √2/2 + √2/2 i

    (We can find this by saying (a + bi)^(2) = i, which gives us (a^(2) - b^(2) = 0 and 2ab = 1) we get a = b from the first, and a^(2) = 1/2)

    The keen eyed observer might notice that this value is also equal to sin(45°) and we start to get some ideas about how all of the complex numbers with radius 1 might be somewhat special and carry their own amount of “positiveness” or “negativeness” that is somehow unique to it.

    So let’s represent these values with R ∠ θ where the θ represents the amount of positiveness or negativeness in some way.

    Since we’ve observed that √i is located at the point 45° from the positive real axis, and i is on the imaginary axis, 90° from the positive real axis, and -1 is 180° from the positive real axis, and if we examine each of these we find that if we use cos to represent the real axis and sin to represent the imaginary axis. That’s really neat. It means we can represent any complex number as R ∠ θ = cos θ + i sin θ.

    What happens if we multiply two complex numbers in this form? Well, it turns out if you remember your trigonometry, you exactly get the angle addition formulas for sin and cos. So R ∠ θ * S ∠ φ = RS ∠ θ + φ. But wait a second. That’s turning multiplication into an addition? Where have we seen something like this before? Exponent rules.

    We have a^(n) * a^(m) = a^(n+m) what if, somehow, this angle formula is also an exponent in disguise?

    Then you’re learning calculus and you come across Taylor Series and you learn a funny thing, the Taylor series of e^x looks a lot like the Taylor series of sine and cosine.

    And actually, if we look at the Taylor series for e^(ix) is exactly matches the Taylor series for cos x + i sin x. So our supposition was correct, it was an exponent in disguise. How wild. Finally we get:

    R ∠ θ = Re^(iθ) = cos θ + i sin θ



  • It’s not a mental disorder to simply be anti-authority, but it can be pathological. Not to take away from your point or anything, but I have a true story about a kid who went to college with my wife.

    He was a real prat who didn’t like being told what to do, and he seemed to take perverse pleasure in antagonizing authority figures who couldn’t directly punish him and who he considered to be beneath him. For instance, he would frequently leave his messy plates out at the dining hall, because he knew there would be no consequences for him, and he wanted the staff to have to clean up after him.

    Or this one time where the RA in the dorm was explaining how to choose a room for next year because everyone had to move out, he had a zippo lighter and was just throwing it up and catching it, and occasionally letting it fall to the ground and make a loud noise. He ignored instructions to stop doing that because it’s obnoxious, because the RA was an authority with no power, so was beneath him.

    All in all, cowardly behavior, and while I’m not a psychiatrist, and I cannot diagnose him, it certainly sounds like ODD to me.

    Anyway, this piece of shit’s name is Stephen Miller.