advent-2015-7.rb

input = File.read("7_input.txt").gsub("OR", "|").gsub("AND", "&").gsub("LSHIFT", "<<").gsub("RSHIFT", ">>").gsub("NOT", "~").lines.map(&:chomp)

@map = {}
input.each do |expression|
  left_side, right_side = expression.split("->")
  @map[right_side.strip] = left_side
end

@memo = {}
def evaluate(label)
  return @memo[label] if @memo[label]

  label.scan(/[a-z]+/).uniq.each do |cap|
    label.gsub!(cap, evaluate(@map[cap]).to_s)
  end

  @memo[label] = eval(label)
end

puts evaluate(@map["a"])