5 ms·

The highlighting and counting is cool but isn't this just colouring prime numbered elements (off by one) by knowing the primes up to √n? Bit of a circular probl

• burnte 9y ago
  I would doubt it's possible, considering the methods that we use to detect primes come down to brute force. It's hard to build an algorithm when we don't have a formal proof of how primes work/can be detected.
  • ecma 9y ago
    Well it's definitely possible unless I'm a moron (correct me if I am). If you have the primes up to √n you can find all primes up to n because everything else will be composite of the primes you know already. This is basically what TFA is doing. What I was suggesting is that it would be cool if you could avoid defining rules explicitly for (3n+6), (5n+10), etc and have them appear from some feedback loop where we go from a sequence of primes up to n, to n^2, to n^4... CSS4, let's do it.
    • gvx 9y ago
      I don't know if CSS is Turing complete already, but I'm pretty sure it would have to be if it allowed you to implement something like that...
      • dkbrk 9y ago
        No, it would only need to be primitive recursive [0] because you can bound its runtime. There's actually a lot you can do without Turing completeness. [0]: https://en.wikipedia.org/wiki/Primitive_recursive_function#Computer_language_definition https://en.wikipedia.org/wiki/Primitive_recursive_function#C...
      • __s 9y ago
        Pure CSS game: https://codepen.io/elad2412/pen/hBaqo https://codepen.io/elad2412/pen/hBaqo Rule110 (After setting first row requires alternation of tab/space to run): https://codepen.io/elrumordelaluz/pen/wqLyH?editors=010 https://codepen.io/elrumordelaluz/pen/wqLyH?editors=010 stackoverflow discussion: https://stackoverflow.com/questions/2497146/is-css-turing-complete https://stackoverflow.com/questions/2497146/is-css-turing-co...
  • nimih 9y ago
    Modern prime testing is quite far from brute force. Tests such as AKS[1], ECPP[2], and APR[3] can determine whether a number is prime in polynomial time (in the number of bits/digits), whereas a true brute force search would be exponential. [1]https://en.wikipedia.org/wiki/AKS_primality_test https://en.wikipedia.org/wiki/AKS_primality_test [2]https://en.wikipedia.org/wiki/Elliptic_curve_primality_proving https://en.wikipedia.org/wiki/Elliptic_curve_primality_provi... [3]https://en.wikipedia.org/wiki/Adleman%E2%80%93Pomerance%E2%80%93Rumely_primality_test https://en.wikipedia.org/wiki/Adleman%E2%80%93Pomerance%E2%8...
    • burnte 9y ago
      You're right, I misspoke I should have been more precise and said that out way of finding primes isn't based on a specific theorem or algorithm in that we still have to take a number and demonstrate its primeness.
• gus_massa 9y ago
  You can use the same trick dividing by all the numbers up to sqrt(n) [or n-1], instead of dividing by prime numbers. You can replace li:first-child, li:nth-child(2n + 4), li:nth-child(3n + 6), li:nth-child(5n + 10), li:nth-child(7n + 14) { color: grey; counter-increment: nature-count nonprime-count; } with li:first-child, li:nth-child(2n + 4), li:nth-child(3n + 6), li:nth-child(4n + 8), li:nth-child(5n + 10), li:nth-child(6n + 12), li:nth-child(7n + 14) li:nth-child(8n + 16) li:nth-child(9n + 18) li:nth-child(10n + 20) { color: grey; counter-increment: nature-count nonprime-count; }