betasilly

Hello fellow J programmer. In statistic you can estimate the population size by coloring fishes that you put in a lake and some time later you fish in that lake, the proportion of colored fishes allow you to estimate the size of the population. Four month ago I posted some J identities [1] and you were the only one which commented, that means that in this capture I only got one fish and it was the colored fish. This imply that there must be very few J programmers HN, or more precisely, very few of them that post J related material.

The parent's comment (also mine) has a style that was designed not to scare non J programmers. One should also consider that some people dislike J code so downvotes are the usual result except when the post provides some additional insight.

Finally, thank you for this small J lesson, is a pleasure to find here fellow J programmers.

[1] https://news.ycombinator.com/item?id=42859077

Another interesting fact is that each time you make the xor of four consecutive numbers, beginning with an even number, the result is zero. Example in J.

  xor =: (16 + 2b0110) b.
  f =: 3 : 'xor/ y + i. 4'
  f"0 ] 2 * 1 + i. 100

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Summing a hundred millions: +/ f"0 ] 2 * i 100000000 gives zero (it takes a few seconds). So it seems the stated property holds for every even n.