Minutes 2024-11-14

Came from RedTeam meeting on LLM jailbreaking
1. Won cool stickers!
2. LUG stickers #soon
Ron's talk on Regex!
1. What is an alphabet
2. Strings are a finite series of characters
  1. We typically use "w" to represent strings, for "word"
  2. Lamba (λ) = empty string
3. Languages are represented by "L"
4. Machine takes strings (w) and determines if it's in the language (L)
5. Finite Automata
  1. Example automata that only accepts an even length string
6. Regular Expressions
  1. ∅ = empty set ={}
  2. r = hello
    1. only accepts the word "hello"
  3. r = a * b
    1. L(r) = {"a", "b"}
    2. The language contains both "a" and "b"
  4. Kleene Star (*)
    1. Only way to represent an infinite number of an expression
    2. r = a*
      1. L(r) = {λ, "a", "aa", "aaa", ...}
    3. r = (ab + c)*
      1. ab + c matches any instance of "ab" or "c"
      2. (ab + c)* = L{λ, "ab", "c", "abab", "abc", "cccab", ...}
      3. r = (d + ∅)
        L(d) = {"d"}
        
        L{∅} = {}
        
        {"d"} ∪ {} = {"d"}
        
        You cannot append "nothing" (AKA ∅) to a string but you can append an empty string (AKA λ)
7. grep + Regex
  1. grep uses an 'extended' version of regex
  2. [] - "any of", [abcd], [0-9]
  3. [^] - "none of", [^aeiuo]
  4. ? - "maybe", colou?r
    1. matches both color and colour
  5. |= +
  6. + - 1-or-more
    1. the Kleene star is essentially '0-or-more'
8. Live demo!
  1. Grepping for strings inside hamlet
    1. grep hamlet
    2. grep 'z.*z' - matching any number of characters between two z's
      1. Specific behavior depends on the implementation, most are greedy
      2. z.*z would likely match "zz" on a line that had "zzz", but some implementations may match "zzz"
    3. Matching all lines with 13 words in them
9. Common Extensions
  1. Groups
    1. In Grep, need to use -P flag for "Perl" mode (-E for "extended" does not allow you to use groups)
  2. Lookaround
    1. Matches text without being part of the matched text
    2. Replacing all instances of "John Smith" with "Jack Smith" in a text file that also has "John Cena"
  3. Replacing all instanced of "hamlet" with "bamlet" using :s/hamlet/bamlet/g in vim
10. Language Theory
  1. What makes a language regular?
  2. if it can be described using a Regular Expression!
11. Regular Automata
  1. Limited state, can only read input once
12. Chomsky's Hierarchy
  1. Regular expressions are at the bottom of this pyramid
  2. Context-free, Context-sensitive, and Recursively enumerable expressions sit above regular expressions, in that order
  3. Turing machines above all of those
  4. Regular expression cannot replace your programming language
  5. Some regular language implementation decide languages that aren't regular! >:(
    1. ^(a(?1)?b)$
    2. More akin to "context-free" expressions
    3. Ron will literally murder them (very real and true)
13. Does Tech teach anything that covers beyond context-free in undergrad?
  1. no :(
What WM does Ron use?
1. Xmonad, customized in a weird way exactly to his liking
  1. A true gentoo user
Why do people call gentoo a "meta-distribution"?
1. They call themselves that, but they're really more like a regular distribution
2. Only time Josh ever heard of "meta-distribution" was in reference to Bedrock Linux, since it's a distro you install other distributions inside of
Does Tech teach pumping lemmas?
1. They were supposed to
2. Josh doesn't remember it
Allen continues his ventures in gaming on one of the GLRC servers
1. Why?
  1. Free power
2. How are you going to get around anticheat?
  1. "idk"
Domino's BOGO deal for more LUG Pizza parties? [1]
Wrapped up briefly talking about recent FOSS drama
1. Stallman report
  1. Drew report
2. Linus is back to his old self on the Linux mailing list
  1. Russian maintainer stuff
  2. BTRFS filesystem
eboard Taco Bell trip