I've been trying to begin a transition from NixOS to Guix, but I'm having a hard time finding where the different symbols referenced in the Guix/Guile manual are defined. For example, I want to use BTRFS on a LUKS-encrypted device, but I can't quite find what to #:use-module for the mapped-devices symbol. That is to say:

(file-system
  (device "/dev/mapper/cryptroot")
  (mount-point "/home")
  (type "btrfs")
  (options "subvol=home")
  (dependencies mapped-devices))

The mapped-devices above is an "unbound variable" (according to the errors). I still don't have this figured out, so how would others go about finding what to "import" since the official examples I'm looking at don't really tell me anything? (unless I'm blind, very likely!)

[–] 3 points 5 months ago

I have an electric kettle, works fine as I don't really do anything "special". The ones with the screen on the base where you can choose temperature are nice for tea and stuff so you don't burn it. I've been meaning to look into getting one

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    Hello all,

    I am growing in an organic medium. I'm somewhat new to growing still as this is only my second grow, first with organic soil. I was wondering how beneficial cover crops would be in my container. I was thinking on using white clover. Even if it isn't totally beneficial, as long as it wouldn't be harmful, it would be nice to keep that ecosystem active

     

    The nth term of a geometric sequence can be written

    a(n) = a(1)*r^(n-1)
    

    We can rewrite the two given equations:

    a(2) + a(4) = 30 = a(1)*r + a(1)*r^3 (Equation 1)
    a(3) + a(5) = 15 = a(1)*r^2 + a(1)*r^4 (Equation 2)
    

    Notice that Equation 1 can be substituted into Equation 2, i.e.,

    a(1)*r^2 + a(1)*r^4 = 15
    r*[a(1)*r + a(1)*r^3] = 15
    r*(30) = 15
    r = 1/2
    

    If we substitute this into Equation 1, we have

    a(1)/2 + a(1)/8 = 30
    a(1) = 30 * 8/5 = 48
    

    The answer is 48. Did he even need to specify that the sum exists? It's a finite geometric sequence so surely it's impossible for the sum not to exist? If you want to stop me old man, ask me the most basic combinatorics question you can think of and I'll start foaming at the mouth.

    Thanks for verifying my answer, Elpam!

    Sauce: The Last Adventurer, Ch. 103

     

    If we look into a far off distance at an object travelling towards Earth, shouldn't we be able to see both the light from the object at some time t plus the light at some later time (t + delta t)?

    Let's also assume that the object is traveling fast enough that it is discernable. This point might be moot, since I'm not sure if such a situation is possible. I know that Rayleigh's criterion could give us a lower bound for how far the images of the object has to be, though I'm not sure how complicated it would be to throw redshift into the mix.

    This seems like one of those "Whoa this feels see weird causally but it's just a natural consequence of things we've observed thus has little repercussions as to what limitations physicists actually work around." Actually, I could see perhaps long exposure photos (or the telescope equivalent, if it exists) could run into issues.

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