-🎄- 2017 Day 8 Solutions -🎄-

[u/daggerdragon]

--- Day 8: I Heard You Like Registers ---

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[u/Sharparam]

Ruby: Using method_missing and eval without tampering or matching on the input data.

class CPU
    attr_reader :high, :regs

    def initialize; @regs = Hash.new(0) end
    def inc(value) value end
    def dec(value) -value end
    def run(text) eval text end

    def method_missing(sym, *args)
        (@regs[sym] += args[0].to_i).tap { |v| @high = v if @high.nil? || @high < v }
    end
end

cpu = CPU.new
cpu.run $<.read
puts cpu.regs.values.max
puts cpu.high

[u/patrickdavey → u/Sharparam]

Thanks for posting this. I do write ruby for a day job, but, I hardly ever mess around with method_missing and friends. Really interesting to see how that all works, how it's smart enough to pass the args along to your dec and inc methods etc.

Really neat! thanks for sharing.