File: throwcatch.rb

Project: throw_catch -- Throw/Catch Lab 

#!/usr/bin/env ruby

CatchStack = []

def cc_catch(sym)
  callcc { |cc|
    CatchStack.push([sym, cc])
    yield
  }
ensure
  CatchStack.pop
end

def cc_throw(sym, value=nil)
  while ! CatchStack.empty? && CatchStack.last[0] != sym
    CatchStack.pop
  end
  fail NameError, "uncaught throw `#{sym}'" if CatchStack.empty?
  CatchStack.last[1].call(value)
end

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