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#!/usr/bin/env ruby # Ruby Quiz 156: Internal Rate of Return # Jesse Merriman, Maxima version # (http://www.jessemerriman.com/project/ltf) require 'ltf' include LTF class Array def map_with_index mapped = [] each_with_index { |x, i| mapped << yield(x, i) } mapped end end if __FILE__ == $0 cash_flows = ARGV[0..-2] accuracy = ARGV[-1].to_i eq = '0 = ' + cash_flows.map_with_index { |x, i| "#{x}/(1+irr)^#{i}" }.join(' + ') max = Maxima.new "fpprec: #{accuracy};" max.puts "res: solve([#{eq}], [irr]);" sols = [] num_sols = max.puts('length(res);').to_i num_sols.times { |i| sols << max.puts("bfloat(res[#{i+1}]);") } real_sols, complex_sols = [], [] sols.each do |s| if /%i/.match(s) complex_sols << s else real_sols << s end end puts 'Real solutions:' puts ' ' + real_sols.join("\n ") puts 'Complex solutions:' puts ' ' + complex_sols.join("\n ") max.quit end

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