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Comment by icen | Hacker News Reader

< grades upwards: for each element, the element of the returned array is its position if the array is sorted.

    x: 10?A:"abcdefghijklmnopqrstuvwxyz"
     x
    "ysyselacwl"
     +`x`y`z!(x;<x;<<x)
    x   y z
    --- - -
    "y" 6 8
    "s" 7 5
    "y" 4 9
    "s" 5 6
    "e" 9 2
    "l" 1 3
    "a" 3 0
    "c" 8 1
    "w" 0 7
    "l" 2 4

So <x gives a sort index, <<x tells you how far each element is from the minimum in that sort index

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I still don’t understand what the numbers in column y mean. I understand column z and that’s also what grade up is returning in John Earnest’s oK:

    x:“baced“
    <x
  1 0 2 4 3
    <<x
  1 0 2 4 3

That is, for example, when sorting, the item at position 1 in the original string (“a”) moves to position 0 (the beginning of the sorted string). So in the end you get “abcde”.

What does column y mean? If I sort the original with it, I get “wllaysysce”.

Has this changed between versions of K?

Nevermind. I've figured it out with the help of the reference manual at http://www.nsl.com/k/k2/k295/kreflite.pdf. I knew it was a permutation but I applied it incorrectly.

yeah, i figured it out eventually. since you seem knowledgeable about K, would you mind taking a look at my second comment in this thread (about inverting permutations) and seeing if it makes sense? thanks!

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