如何在哈希中将键的值设置为另外两个键的值的差值？

Question

我想设置＆＃34; vars [＆＃39; dif＆＃39;]＆＃34;根据＆＃34; globalvars [＆＃39; days＆＃39;]＆＃34;的价值差异和＆＃34; globalvars [＆＃39;供应＆＃39;]＆＃34; （设置＆＃39; dif＆＃39;天＆＃39; - ＆＃39;供应＆＃39;）

任何能告诉我如何做到这一点的答案都会有所帮助，即使这意味着我需要完全改变我的代码，但我更希望它以我保存代码的方式完成。

globalvars = { 'days' => 0 , 'supplies' => 0 }

puts "Please input the number of days the trip will take."
globalvars['days'] = gets.chomp
puts "Please input the number of days worth of supplies each person can carry."
globalvars['supplies'] = gets.chomp
puts globalvars

puts ;
puts "Press RETURN to continue."
gets


if (globalvars['days'] <= globalvars['supplies'])
    then
    puts "No helpers are needed."
    puts "Press RETURN to continue."
    gets
else
    puts "Helpers are needed."
    puts "Press RETURN to continue."
    gets
end


vars = { 'man' => 0 , 'varx' => 0 , 'dif' => 0 }
vars['man'] = globalvars['supplies']
vars['dif'] = globalvars['days'] - globalvars['supplies'] "< this is the line"

puts vars


puts ;
puts "Press RETURN to exit."
gets

如果有人知道如何使获取命令只接受某个键，例如输入，按下，请将其添加到您的答案中。