ski.rb

expr_gen = -> (n) { "(?<expr#{n}>[^()]|\\(\\g<expr#{n}>+\\))" }
simple = '(?<simple>(?:[()]|[^ski])*)'

S = /^#{simple}s#{expr_gen.(1)}#{expr_gen.(2)}#{expr_gen.(3)}(?<rest>.*)/
K = /^#{simple}k#{expr_gen.(1)}#{expr_gen.(2)}(?<rest>.*)$/
I = /^#{simple}i(?<rest>.+)/
P = /^#{simple}\((?<content>#{expr_gen.(1)}*)\)(?<rest>.*)/

$s = '\k<simple>(\k<expr1>\k<expr3>)(\k<expr2>\k<expr3>)\k<rest>'
$k = '\k<simple>\k<expr1>\k<rest>'
$i = '\k<simple>\k<rest>'
$p = '\k<simple>\k<content>\k<rest>'

def ski(str)
  () while str.gsub!(S, $s) ||
           str.gsub!(K, $k) ||
           str.gsub!(I, $i) ||
           str.gsub!(P, $p)
  str
end


p ski('sxyza') == 'xzyza'
p ski('kxy') == 'x'
p ski('ixx') == 'xx'
p ski('(x)y') == 'xy'
p ski('kixy') == 'y'
p ski('(ix)') == 'x'
p ski('s(k(si))kAB') == 'BA'

X = /#{simple}$/
$x = 'echo \k<simple>'

Y = /(?<content>.*[ski].*)$/
$y = 'echo ruboty ski \k<content>'


[S, $s, K, $k, P, $p, I, $i].each_slice(2) do |a, b|
  puts "ruboty replace ^ruboty ski #{a.inspect[2..-2]} with ruboty ski #{b}"
end

[X, $x, Y, $y].each_slice(2) do |a, b|
  puts "ruboty replace ^ruboty ski #{a.inspect[1..-2]} with ruboty #{b}"
end

https://pocke.hatenablog.com/entry/2020/01/30/020916