README

I made this file to scratch an itch. I'm learning Python and I found they have "new" control flows. They have a while/else. This made me go to Wikipedia and see if there were any others I was ignoring. This in turn made me come to exit_when. It's like a Case statement with a While mixed in.

Will I ever use it? Dunno. Have I found any useful scenario? Not yet.

(I'm sure a better Rubyist can make a better implementation. If someone knows a better way, please let me know.)

Enjoy.

exit_when.rb

def infinite_loop
  yield while(true)
end
def exit_when(options)
  found = false
  result = nil
  result_yield = nil
  infinite_loop {
    result_yield = yield
    if (options.keys.include? result_yield) ||
       (options.keys.include? result_yield.class and 
        result_yield = result_yield.class)
      result = options[result_yield]
      break
    end
  }
  if result.is_a? Proc
    result.call(result_yield)
  else
    result
  end
end

def while_else(clauses)
  called_once = false
  while (clauses[:condition].call) do
    called_once = true
    clauses[:body].call
  end
  clauses[:else].call unless called_once
end

if __FILE__ == $0
  rslt = exit_when(
    1 => 'one',
    Symbol => proc {|x| puts x},
  '12' => String
  ) {
    number = (rand * 15).floor
    puts number
    ('12' if number == 12) or
    (:even if number % 2 == 0) or
    number
  }
  puts rslt unless rslt.nil?

  def buy_upgrades(credits_available)
    while_else({ :condition => proc {credits_available > 0},
      :body => proc{credits_available -= (rand * 3).floor
        puts "#{credits_available} left"},
          :else => proc{puts "No upgrade possible."}
    })
  end

  puts "----------------"
  buy_upgrades(10)
  puts "----------------"
  buy_upgrades(0)
end