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Ruboty and
SKI
Meguro.rb #30
2020-01-31 Fri.
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pp self
● Masataka “pocke” Kuwabara
● Work for BIt Journey, Inc.
● Live in ruby-jp.slack.com
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Agenda
● I implemented SKI combinator calculus with
Ruboty, so I’ll describe the implemetation
○ What’s Ruboty
○ What’s SKI combinator calculus
○ How implement SKI combinator calculus in
Ruboty
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What’s Ruboty
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Ruboty
● A chat bot framework written in Ruby
● https://github.com/r7kamura/ruboty
● Customizable by plugins written in Ruby
● Ruboty lives in ruby-jp.slack.com
○ Join us from https://ruby-jp.github.io/!
○ It is developed in
https://github.com/pocke/ruboty-ruby-jp.
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Ruboty example
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What’s SKI combinator
calculus
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I’m not sure!!!
● I’m not familiar with it
● But, I’ll try to describe it!
● Please give me advices if I’m wrong
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SKI combinator calculus
● A programming language (maybe)
● The program examples:
○ Ix, Kxy, Sxyz
○ S(K(SI))Kxy
● It replaces itself with 3 rules
○ The rules are S, K and I
● I’ll describe rule with reversed order
● It manipulates a string in this slide, but actually
it manipulates a tree in general
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Rule I
● “I” takes one argument and returns it
● In other words, it’s just removed
● For example:
○ Ix => x
○ Iy => y
○ IIx => Ix => x
○ Ixyz => xyz
○ I(xyz) => xyz
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Rule K
● “K” takes two arguments and returns the first
one
● For example:
○ Kxy => x
○ K(xyz)(abc) => xyz
○ Kixy => iy => y
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Rule S
● It takes three arguments, and returns “first
third(second third)”
● For example:
○ Sxyz => xz(yz)
○ S(K(SI))Kxy => K(SI)x(Kx)y => SI(Kx)y =>
Iy(Kxy) => y(Kxy) => yx
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How implement
SKI combinator calculus in
Ruboty
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The easiest way: Create a plugin
● We can create a plugin with writing the
algorithm in Ruby
● But it is not interesting! It is too easy!
● So, I went to more difficult way
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More difficult way: Combination of plugins
● We can combine plugins to implement SKI
combinator calculus
● I used taiki45/ruboty-echo and
r7kamura/ruboty-replace
● I’ll describe these plguins
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ruboty-echo
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ruboty-echo
● “Ruboty repeats everything...”
● It’s super simple.
● ruboty echo hello
○ => Ruboty says “hello”
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HACK: ruboty reacts itself
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ruboty-replace
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ruboty-replace
● “Replace given message with registered
patterns for other handlers.”
● Like alias
● example
○ ruboty replace hello (.+) with
echo こんにちは \1 さん
○ “ruboty hello pocke”
will be replaced with
“ruboty echo こんにちは pocke さん”
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String#gsub!
● ruboty-replace just uses String#gsub!
● For example:
○ ruboty replace hello (.+) with
echo こんにちは \1 さん
○ msg.gsub!(/hello (.+)/,
“echo こんにちは \1 さん”)
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Combine them
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Make a loop (DO NOT TRY IT⚠)
● We can make an infinite loop with them easily
● Just say the following command⚠
○ ruboty replace loop with echo ruboty loop
● If you say “ruboty loop”,
ruboty says “ruboty loop”,
then ruboty says “ruboty loop”,
then ruboty says “ruboty loop”,
then ruboty says “ruboty loop”,
then ruboty says “ruboty loop”,
then ruboty says “ruboty loop”,
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It means we get “while” expression
● It equals “while true do … end”
● And, we already have String#gsub! by
ruboty-replace
● If we can implement SKI only by “while” and
gsub!, we can implement SKI with the plugins
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The regular expressions
(?(?:[()]|[^ski])*)s(?[^()]|\(\g
+\))(?[^()]|\(\g+\))(?[^()]|\(\g<
expr3>+\))(?.*)
(?(?:[()]|[^ski])*)k(?[^()]|\(\g
+\))(?[^()]|\(\g+\))(?.*)$
(?(?:[()]|[^ski])*)\((?(?[^()]
|\(\g+\))*)\)(?.*)
(?(?:[()]|[^ski])*)i(?.+)
(?(?:[()]|[^ski])*)$
(?.*[ski].*)$
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The result
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How create the
regexps
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expr_gen
expr_gen = -> (n) {
"(?
[^()] |
\\(\\g+\\))
"
}
● Generate a string that matches an “expression”
● Recursive regexp by “\g”
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simple
simple =
'(?(?:
[()] |
[^ski])*)
'
● String that matches simple string
● Simple string is not calculated
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I
I = /^#{simple}i(?.+)/
$i = '\k\k'
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K
K =
/^#{simple}k#{expr_gen.(1)}#{expr_ge
n.(2)}(?.*)$/
$k = '\k\k\k'
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S
S =
/^#{simple}s#{expr_gen.(1)}#{expr_ge
n.(2)}#{expr_gen.(3)}(?.*)/
$s =
'\k(\k\k)(\k\k)\k'
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Reduce parens
P =
/^#{simple}\((?#{expr_gen.(
1)}*)\)(?.*)/
$p = '\k\k\k'
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while and gsub!
def ski(str)
() while str.gsub!(S, $s) ||
str.gsub!(K, $k) ||
str.gsub!(I, $i) ||
str.gsub!(P, $p)
str
end
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Conclusion
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Conclusion
● We learn Ruboty and SKI, and Regexp
● We can implement SKI in Slack without “code”
● For more information:
○ The Ruby program: https://bit.ly/2RI1Ckd
○ Japanese blog: https://bit.ly/2vs0fNE
Thanks for listening!