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Life & fun · August 23, 2018

PN

Prime Number Regex

I was messing around representing integers using binary trees, and noticed that a certain tree format makes it trivial to grep for prime numbers. Probably not very novel, but thought y'all might enjoy it. Here's one through sixteen: * (()()) * ((()())()) * (((()())())()) (((()())())(()())) * ((((()())())())()) ((((()())())())(()())) * ((((()())())(()()))()) ((((()())())(()()))(()())) ((((()())())(()()))((()())())) ((((()())())(()()))(((()())())())) * (((((()())())())())()) (((((()())())())())(()())) * (((((()())())())(()()))()) (((((()())())())(()()))(()()))…

Alternatives

What it does

In the maker’s words, at launch

I was messing around representing integers using binary trees, and noticed that a certain tree format makes it trivial to grep for prime numbers. Probably not very novel, but thought y'all might enjoy it. Here's one through sixteen: * (()()) * ((()())()) * (((()())())()) (((()())())(()())) * ((((()())())())()) ((((()())())())(()())) * ((((()())())(()()))()) ((((()())())(()()))(()())) ((((()())())(()()))((()())())) ((((()())())(()()))(((()())())())) * (((((()())())())())()) (((((()())())())())(()())) * (((((()())())())(()()))()) (((((()())())())(()()))(()())) (((((()())())())(()()))((()())())) (((((()())())())(()()))(((()())())())) I added asterisks in front of the primes. Here's the set of 16-bit ints: https://gist.github.com/cieplak/213fb4c88581d8971b274b7ec647... The regex just checks if the string ends with '())': cat integers.txt | grep '())$' | nl | tail -1

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